CINXE.COM

<!DOCTYPE html> <html class="client-nojs vector-feature-language-in-header-enabled vector-feature-language-in-main-page-header-disabled vector-feature-page-tools-pinned-disabled vector-feature-toc-pinned-clientpref-1 vector-feature-main-menu-pinned-disabled vector-feature-limited-width-clientpref-1 vector-feature-limited-width-content-enabled vector-feature-custom-font-size-clientpref-1 vector-feature-appearance-pinned-clientpref-1 vector-feature-night-mode-enabled skin-theme-clientpref-day vector-sticky-header-enabled vector-toc-available" lang="en" dir="ltr"> <head> <meta charset="UTF-8"> <title>Altruism (biology) - Wikipedia</title> <script>(function(){var className="client-js vector-feature-language-in-header-enabled vector-feature-language-in-main-page-header-disabled vector-feature-page-tools-pinned-disabled vector-feature-toc-pinned-clientpref-1 vector-feature-main-menu-pinned-disabled vector-feature-limited-width-clientpref-1 vector-feature-limited-width-content-enabled vector-feature-custom-font-size-clientpref-1 vector-feature-appearance-pinned-clientpref-1 vector-feature-night-mode-enabled skin-theme-clientpref-day vector-sticky-header-enabled vector-toc-available";var cookie=document.cookie.match(/(?:^|; )enwikimwclientpreferences=([^;]+)/);if(cookie){cookie[1].split('%2C').forEach(function(pref){className=className.replace(new RegExp('(^| )'+pref.replace(/-clientpref-\w+$|[^\w-]+/g,'')+'-clientpref-\\w+( |$)'),'$1'+pref+'$2');});}document.documentElement.className=className;}());RLCONF={"wgBreakFrames":false,"wgSeparatorTransformTable":["",""],"wgDigitTransformTable":["",""],"wgDefaultDateFormat":"dmy","wgMonthNames":["","January","February","March","April","May","June","July","August","September","October","November","December"],"wgRequestId":"06ac60d7-72b7-4114-9535-80f8495b7d84","wgCanonicalNamespace":"","wgCanonicalSpecialPageName":false,"wgNamespaceNumber":0,"wgPageName":"Altruism_(biology)","wgTitle":"Altruism (biology)","wgCurRevisionId":1282159263,"wgRevisionId":1282159263,"wgArticleId":2021591,"wgIsArticle":true,"wgIsRedirect":false,"wgAction":"view","wgUserName":null,"wgUserGroups":["*"],"wgCategories":["CS1 German-language sources (de)","Webarchive template wayback links","Articles with short description","Short description is different from Wikidata","Use mdy dates from February 2015","Wikipedia articles needing clarification from August 2014","All articles with unsourced statements","Articles with unsourced statements from August 2022","Behavioral ecology","Ethology","Altruism","Evolutionary psychology"],"wgPageViewLanguage":"en","wgPageContentLanguage":"en","wgPageContentModel":"wikitext","wgRelevantPageName":"Altruism_(biology)","wgRelevantArticleId":2021591,"wgIsProbablyEditable":true,"wgRelevantPageIsProbablyEditable":true,"wgRestrictionEdit":[],"wgRestrictionMove":[],"wgNoticeProject":"wikipedia","wgCiteReferencePreviewsActive":false,"wgFlaggedRevsParams":{"tags":{"status":{"levels":1}}},"wgMediaViewerOnClick":true,"wgMediaViewerEnabledByDefault":true,"wgPopupsFlags":0,"wgVisualEditor":{"pageLanguageCode":"en","pageLanguageDir":"ltr","pageVariantFallbacks":"en"},"wgMFDisplayWikibaseDescriptions":{"search":true,"watchlist":true,"tagline":false,"nearby":true},"wgWMESchemaEditAttemptStepOversample":false,"wgWMEPageLength":60000,"wgEditSubmitButtonLabelPublish":true,"wgULSPosition":"interlanguage","wgULSisCompactLinksEnabled":false,"wgVector2022LanguageInHeader":true,"wgULSisLanguageSelectorEmpty":false,"wgWikibaseItemId":"Q2559380","wgCheckUserClientHintsHeadersJsApi":["brands","architecture","bitness","fullVersionList","mobile","model","platform","platformVersion"],"GEHomepageSuggestedEditsEnableTopics":true,"wgGETopicsMatchModeEnabled":false,"wgGELevelingUpEnabledForUser":false}; RLSTATE={"ext.globalCssJs.user.styles":"ready","site.styles":"ready","user.styles":"ready","ext.globalCssJs.user":"ready","user":"ready","user.options":"loading","ext.cite.styles":"ready","skins.vector.search.codex.styles":"ready","skins.vector.styles":"ready","skins.vector.icons":"ready","jquery.makeCollapsible.styles":"ready","ext.wikimediamessages.styles":"ready","ext.visualEditor.desktopArticleTarget.noscript":"ready","ext.uls.interlanguage":"ready","wikibase.client.init":"ready","ext.wikimediaBadges":"ready"};RLPAGEMODULES=["ext.cite.ux-enhancements","mediawiki.page.media","site","mediawiki.page.ready","jquery.makeCollapsible","mediawiki.toc","skins.vector.js","ext.centralNotice.geoIP","ext.centralNotice.startUp","ext.gadget.ReferenceTooltips","ext.gadget.switcher","ext.urlShortener.toolbar","ext.centralauth.centralautologin","mmv.bootstrap","ext.popups","ext.visualEditor.desktopArticleTarget.init","ext.visualEditor.targetLoader","ext.echo.centralauth","ext.eventLogging","ext.wikimediaEvents","ext.navigationTiming","ext.uls.interface","ext.cx.eventlogging.campaigns","ext.cx.uls.quick.actions","wikibase.client.vector-2022","ext.checkUser.clientHints","ext.quicksurveys.init","ext.growthExperiments.SuggestedEditSession"];</script> <script>(RLQ=window.RLQ||[]).push(function(){mw.loader.impl(function(){return["user.options@12s5i",function($,jQuery,require,module){mw.user.tokens.set({"patrolToken":"+\\","watchToken":"+\\","csrfToken":"+\\"}); }];});});</script> <link rel="stylesheet" href="/w/load.php?lang=en&modules=ext.cite.styles%7Cext.uls.interlanguage%7Cext.visualEditor.desktopArticleTarget.noscript%7Cext.wikimediaBadges%7Cext.wikimediamessages.styles%7Cjquery.makeCollapsible.styles%7Cskins.vector.icons%2Cstyles%7Cskins.vector.search.codex.styles%7Cwikibase.client.init&only=styles&skin=vector-2022"> <script async="" src="/w/load.php?lang=en&modules=startup&only=scripts&raw=1&skin=vector-2022"></script> <meta name="ResourceLoaderDynamicStyles" content=""> <link rel="stylesheet" href="/w/load.php?lang=en&modules=site.styles&only=styles&skin=vector-2022"> <meta name="generator" content="MediaWiki 1.44.0-wmf.22"> <meta name="referrer" content="origin"> <meta name="referrer" content="origin-when-cross-origin"> <meta name="robots" content="max-image-preview:standard"> <meta name="format-detection" content="telephone=no"> <meta property="og:image" content="https://upload.wikimedia.org/wikipedia/commons/thumb/b/b5/Grooming_monkeys.jpg/1200px-Grooming_monkeys.jpg"> <meta property="og:image:width" content="1200"> <meta property="og:image:height" content="854"> <meta property="og:image" content="https://upload.wikimedia.org/wikipedia/commons/thumb/b/b5/Grooming_monkeys.jpg/960px-Grooming_monkeys.jpg"> <meta property="og:image:width" content="800"> <meta property="og:image:height" content="569"> <meta property="og:image:width" content="640"> <meta property="og:image:height" content="456"> <meta name="viewport" content="width=1120"> <meta property="og:title" content="Altruism (biology) - Wikipedia"> <meta property="og:type" content="website"> <link rel="preconnect" href="//upload.wikimedia.org"> <link rel="alternate" media="only screen and (max-width: 640px)" href="//en.m.wikipedia.org/wiki/Altruism_(biology)"> <link rel="alternate" type="application/x-wiki" title="Edit this page" href="/w/index.php?title=Altruism_(biology)&action=edit"> <link rel="apple-touch-icon" href="/static/apple-touch/wikipedia.png"> <link rel="icon" href="/static/favicon/wikipedia.ico"> <link rel="search" type="application/opensearchdescription+xml" href="/w/rest.php/v1/search" title="Wikipedia (en)"> <link rel="EditURI" type="application/rsd+xml" href="//en.wikipedia.org/w/api.php?action=rsd"> <link rel="canonical" href="https://en.wikipedia.org/wiki/Altruism_(biology)"> <link rel="license" href="https://creativecommons.org/licenses/by-sa/4.0/deed.en"> <link rel="alternate" type="application/atom+xml" title="Wikipedia Atom feed" href="/w/index.php?title=Special:RecentChanges&feed=atom"> <link rel="dns-prefetch" href="//meta.wikimedia.org" /> <link rel="dns-prefetch" href="login.wikimedia.org"> </head> <body class="skin--responsive skin-vector skin-vector-search-vue mediawiki ltr sitedir-ltr mw-hide-empty-elt ns-0 ns-subject mw-editable page-Altruism_biology rootpage-Altruism_biology skin-vector-2022 action-view"><a class="mw-jump-link" href="#bodyContent">Jump to content</a> <div class="vector-header-container"> <header class="vector-header mw-header"> <div class="vector-header-start"> <nav class="vector-main-menu-landmark" aria-label="Site"> <div id="vector-main-menu-dropdown" class="vector-dropdown vector-main-menu-dropdown vector-button-flush-left vector-button-flush-right" title="Main menu" > <input type="checkbox" id="vector-main-menu-dropdown-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-main-menu-dropdown" class="vector-dropdown-checkbox " aria-label="Main menu" > <label id="vector-main-menu-dropdown-label" for="vector-main-menu-dropdown-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-menu mw-ui-icon-wikimedia-menu"></span> <span class="vector-dropdown-label-text">Main menu</span> </label> <div class="vector-dropdown-content"> <div id="vector-main-menu-unpinned-container" class="vector-unpinned-container"> <div id="vector-main-menu" class="vector-main-menu vector-pinnable-element"> <div class="vector-pinnable-header vector-main-menu-pinnable-header vector-pinnable-header-unpinned" data-feature-name="main-menu-pinned" data-pinnable-element-id="vector-main-menu" data-pinned-container-id="vector-main-menu-pinned-container" data-unpinned-container-id="vector-main-menu-unpinned-container" > <div class="vector-pinnable-header-label">Main menu</div> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-pin-button" data-event-name="pinnable-header.vector-main-menu.pin">move to sidebar</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-main-menu.unpin">hide</button> </div> <div id="p-navigation" class="vector-menu mw-portlet mw-portlet-navigation" > <div class="vector-menu-heading"> Navigation </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="n-mainpage-description" class="mw-list-item"><a href="/wiki/Main_Page" title="Visit the main page [z]" accesskey="z"><span>Main page</span></a></li><li id="n-contents" class="mw-list-item"><a href="/wiki/Wikipedia:Contents" title="Guides to browsing Wikipedia"><span>Contents</span></a></li><li id="n-currentevents" class="mw-list-item"><a href="/wiki/Portal:Current_events" title="Articles related to current events"><span>Current events</span></a></li><li id="n-randompage" class="mw-list-item"><a href="/wiki/Special:Random" title="Visit a randomly selected article [x]" accesskey="x"><span>Random article</span></a></li><li id="n-aboutsite" class="mw-list-item"><a href="/wiki/Wikipedia:About" title="Learn about Wikipedia and how it works"><span>About Wikipedia</span></a></li><li id="n-contactpage" class="mw-list-item"><a href="//en.wikipedia.org/wiki/Wikipedia:Contact_us" title="How to contact Wikipedia"><span>Contact us</span></a></li> </ul> </div> </div> <div id="p-interaction" class="vector-menu mw-portlet mw-portlet-interaction" > <div class="vector-menu-heading"> Contribute </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="n-help" class="mw-list-item"><a href="/wiki/Help:Contents" title="Guidance on how to use and edit Wikipedia"><span>Help</span></a></li><li id="n-introduction" class="mw-list-item"><a href="/wiki/Help:Introduction" title="Learn how to edit Wikipedia"><span>Learn to edit</span></a></li><li id="n-portal" class="mw-list-item"><a href="/wiki/Wikipedia:Community_portal" title="The hub for editors"><span>Community portal</span></a></li><li id="n-recentchanges" class="mw-list-item"><a href="/wiki/Special:RecentChanges" title="A list of recent changes to Wikipedia [r]" accesskey="r"><span>Recent changes</span></a></li><li id="n-upload" class="mw-list-item"><a href="/wiki/Wikipedia:File_upload_wizard" title="Add images or other media for use on Wikipedia"><span>Upload file</span></a></li><li id="n-specialpages" class="mw-list-item"><a href="/wiki/Special:SpecialPages"><span>Special pages</span></a></li> </ul> </div> </div> </div> </div> </div> </div> </nav> <a href="/wiki/Main_Page" class="mw-logo"> <img class="mw-logo-icon" src="/static/images/icons/wikipedia.png" alt="" aria-hidden="true" height="50" width="50"> <span class="mw-logo-container skin-invert"> <img class="mw-logo-wordmark" alt="Wikipedia" src="/static/images/mobile/copyright/wikipedia-wordmark-en.svg" style="width: 7.5em; height: 1.125em;"> <img class="mw-logo-tagline" alt="The Free Encyclopedia" src="/static/images/mobile/copyright/wikipedia-tagline-en.svg" width="117" height="13" style="width: 7.3125em; height: 0.8125em;"> </span> </a> </div> <div class="vector-header-end"> <div id="p-search" role="search" class="vector-search-box-vue vector-search-box-collapses vector-search-box-show-thumbnail vector-search-box-auto-expand-width vector-search-box"> <a href="/wiki/Special:Search" class="cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only search-toggle" title="Search Wikipedia [f]" accesskey="f"><span class="vector-icon mw-ui-icon-search mw-ui-icon-wikimedia-search"></span> <span>Search</span> </a> <div class="vector-typeahead-search-container"> <div class="cdx-typeahead-search cdx-typeahead-search--show-thumbnail cdx-typeahead-search--auto-expand-width"> <form action="/w/index.php" id="searchform" class="cdx-search-input cdx-search-input--has-end-button"> <div id="simpleSearch" class="cdx-search-input__input-wrapper" data-search-loc="header-moved"> <div class="cdx-text-input cdx-text-input--has-start-icon"> <input class="cdx-text-input__input" type="search" name="search" placeholder="Search Wikipedia" aria-label="Search Wikipedia" autocapitalize="sentences" title="Search Wikipedia [f]" accesskey="f" id="searchInput" > <span class="cdx-text-input__icon cdx-text-input__start-icon"></span> </div> <input type="hidden" name="title" value="Special:Search"> </div> <button class="cdx-button cdx-search-input__end-button">Search</button> </form> </div> </div> </div> <nav class="vector-user-links vector-user-links-wide" aria-label="Personal tools"> <div class="vector-user-links-main"> <div id="p-vector-user-menu-preferences" class="vector-menu mw-portlet emptyPortlet" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> </ul> </div> </div> <div id="p-vector-user-menu-userpage" class="vector-menu mw-portlet emptyPortlet" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> </ul> </div> </div> <nav class="vector-appearance-landmark" aria-label="Appearance"> <div id="vector-appearance-dropdown" class="vector-dropdown " title="Change the appearance of the page's font size, width, and color" > <input type="checkbox" id="vector-appearance-dropdown-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-appearance-dropdown" class="vector-dropdown-checkbox " aria-label="Appearance" > <label id="vector-appearance-dropdown-label" for="vector-appearance-dropdown-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-appearance mw-ui-icon-wikimedia-appearance"></span> <span class="vector-dropdown-label-text">Appearance</span> </label> <div class="vector-dropdown-content"> <div id="vector-appearance-unpinned-container" class="vector-unpinned-container"> </div> </div> </div> </nav> <div id="p-vector-user-menu-notifications" class="vector-menu mw-portlet emptyPortlet" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> </ul> </div> </div> <div id="p-vector-user-menu-overflow" class="vector-menu mw-portlet" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="pt-sitesupport-2" class="user-links-collapsible-item mw-list-item user-links-collapsible-item"><a data-mw="interface" href="https://donate.wikimedia.org/?wmf_source=donate&wmf_medium=sidebar&wmf_campaign=en.wikipedia.org&uselang=en" class=""><span>Donate</span></a> </li> <li id="pt-createaccount-2" class="user-links-collapsible-item mw-list-item user-links-collapsible-item"><a data-mw="interface" href="/w/index.php?title=Special:CreateAccount&returnto=Altruism+%28biology%29" title="You are encouraged to create an account and log in; however, it is not mandatory" class=""><span>Create account</span></a> </li> <li id="pt-login-2" class="user-links-collapsible-item mw-list-item user-links-collapsible-item"><a data-mw="interface" href="/w/index.php?title=Special:UserLogin&returnto=Altruism+%28biology%29" title="You're encouraged to log in; however, it's not mandatory. [o]" accesskey="o" class=""><span>Log in</span></a> </li> </ul> </div> </div> </div> <div id="vector-user-links-dropdown" class="vector-dropdown vector-user-menu vector-button-flush-right vector-user-menu-logged-out" title="Log in and more options" > <input type="checkbox" id="vector-user-links-dropdown-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-user-links-dropdown" class="vector-dropdown-checkbox " aria-label="Personal tools" > <label id="vector-user-links-dropdown-label" for="vector-user-links-dropdown-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-ellipsis mw-ui-icon-wikimedia-ellipsis"></span> <span class="vector-dropdown-label-text">Personal tools</span> </label> <div class="vector-dropdown-content"> <div id="p-personal" class="vector-menu mw-portlet mw-portlet-personal user-links-collapsible-item" title="User menu" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="pt-sitesupport" class="user-links-collapsible-item mw-list-item"><a href="https://donate.wikimedia.org/?wmf_source=donate&wmf_medium=sidebar&wmf_campaign=en.wikipedia.org&uselang=en"><span>Donate</span></a></li><li id="pt-createaccount" class="user-links-collapsible-item mw-list-item"><a href="/w/index.php?title=Special:CreateAccount&returnto=Altruism+%28biology%29" title="You are encouraged to create an account and log in; however, it is not mandatory"><span class="vector-icon mw-ui-icon-userAdd mw-ui-icon-wikimedia-userAdd"></span> <span>Create account</span></a></li><li id="pt-login" class="user-links-collapsible-item mw-list-item"><a href="/w/index.php?title=Special:UserLogin&returnto=Altruism+%28biology%29" title="You're encouraged to log in; however, it's not mandatory. [o]" accesskey="o"><span class="vector-icon mw-ui-icon-logIn mw-ui-icon-wikimedia-logIn"></span> <span>Log in</span></a></li> </ul> </div> </div> <div id="p-user-menu-anon-editor" class="vector-menu mw-portlet mw-portlet-user-menu-anon-editor" > <div class="vector-menu-heading"> Pages for logged out editors <a href="/wiki/Help:Introduction" aria-label="Learn more about editing"><span>learn more</span></a> </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="pt-anoncontribs" class="mw-list-item"><a href="/wiki/Special:MyContributions" title="A list of edits made from this IP address [y]" accesskey="y"><span>Contributions</span></a></li><li id="pt-anontalk" class="mw-list-item"><a href="/wiki/Special:MyTalk" title="Discussion about edits from this IP address [n]" accesskey="n"><span>Talk</span></a></li> </ul> </div> </div> </div> </div> </nav> </div> </header> </div> <div class="mw-page-container"> <div class="mw-page-container-inner"> <div class="vector-sitenotice-container"> <div id="siteNotice"></div> </div> <div class="vector-column-start"> <div class="vector-main-menu-container"> <div id="mw-navigation"> <nav id="mw-panel" class="vector-main-menu-landmark" aria-label="Site"> <div id="vector-main-menu-pinned-container" class="vector-pinned-container"> </div> </nav> </div> </div> <div class="vector-sticky-pinned-container"> <nav id="mw-panel-toc" aria-label="Contents" data-event-name="ui.sidebar-toc" class="mw-table-of-contents-container vector-toc-landmark"> <div id="vector-toc-pinned-container" class="vector-pinned-container"> <div id="vector-toc" class="vector-toc vector-pinnable-element"> <div class="vector-pinnable-header vector-toc-pinnable-header vector-pinnable-header-pinned" data-feature-name="toc-pinned" data-pinnable-element-id="vector-toc" > <h2 class="vector-pinnable-header-label">Contents</h2> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-pin-button" data-event-name="pinnable-header.vector-toc.pin">move to sidebar</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-toc.unpin">hide</button> </div> <ul class="vector-toc-contents" id="mw-panel-toc-list"> <li id="toc-mw-content-text" class="vector-toc-list-item vector-toc-level-1"> <a href="#" class="vector-toc-link"> <div class="vector-toc-text">(Top)</div> </a> </li> <li id="toc-Overview" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Overview"> <div class="vector-toc-text"> <span class="vector-toc-numb">1</span> <span>Overview</span> </div> </a> <ul id="toc-Overview-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Implications_in_evolutionary_theory" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Implications_in_evolutionary_theory"> <div class="vector-toc-text"> <span class="vector-toc-numb">2</span> <span>Implications in evolutionary theory</span> </div> </a> <ul id="toc-Implications_in_evolutionary_theory-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Reciprocity_mechanisms" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Reciprocity_mechanisms"> <div class="vector-toc-text"> <span class="vector-toc-numb">3</span> <span>Reciprocity mechanisms</span> </div> </a> <button aria-controls="toc-Reciprocity_mechanisms-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Reciprocity mechanisms subsection</span> </button> <ul id="toc-Reciprocity_mechanisms-sublist" class="vector-toc-list"> <li id="toc-Symmetry-based" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Symmetry-based"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.1</span> <span>Symmetry-based</span> </div> </a> <ul id="toc-Symmetry-based-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Attitudinal" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Attitudinal"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.2</span> <span>Attitudinal</span> </div> </a> <ul id="toc-Attitudinal-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Calculated" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Calculated"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.3</span> <span>Calculated</span> </div> </a> <ul id="toc-Calculated-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Biological_market_theory" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Biological_market_theory"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>Biological market theory</span> </div> </a> <ul id="toc-Biological_market_theory-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Examples_in_vertebrates" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Examples_in_vertebrates"> <div class="vector-toc-text"> <span class="vector-toc-numb">5</span> <span>Examples in vertebrates</span> </div> </a> <button aria-controls="toc-Examples_in_vertebrates-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Examples in vertebrates subsection</span> </button> <ul id="toc-Examples_in_vertebrates-sublist" class="vector-toc-list"> <li id="toc-Mammals" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Mammals"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.1</span> <span>Mammals</span> </div> </a> <ul id="toc-Mammals-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Birds" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Birds"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.2</span> <span>Birds</span> </div> </a> <ul id="toc-Birds-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Fish" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Fish"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.3</span> <span>Fish</span> </div> </a> <ul id="toc-Fish-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Examples_in_invertebrates" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Examples_in_invertebrates"> <div class="vector-toc-text"> <span class="vector-toc-numb">6</span> <span>Examples in invertebrates</span> </div> </a> <ul id="toc-Examples_in_invertebrates-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Examples_in_protists" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Examples_in_protists"> <div class="vector-toc-text"> <span class="vector-toc-numb">7</span> <span>Examples in protists</span> </div> </a> <ul id="toc-Examples_in_protists-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Examples_in_plants" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Examples_in_plants"> <div class="vector-toc-text"> <span class="vector-toc-numb">8</span> <span>Examples in plants</span> </div> </a> <ul id="toc-Examples_in_plants-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-See_also" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#See_also"> <div class="vector-toc-text"> <span class="vector-toc-numb">9</span> <span>See also</span> </div> </a> <ul id="toc-See_also-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Foot_note" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Foot_note"> <div class="vector-toc-text"> <span class="vector-toc-numb">10</span> <span>Foot note</span> </div> </a> <ul id="toc-Foot_note-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-References" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#References"> <div class="vector-toc-text"> <span class="vector-toc-numb">11</span> <span>References</span> </div> </a> <ul id="toc-References-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Further_reading" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Further_reading"> <div class="vector-toc-text"> <span class="vector-toc-numb">12</span> <span>Further reading</span> </div> </a> <ul id="toc-Further_reading-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-External_links" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#External_links"> <div class="vector-toc-text"> <span class="vector-toc-numb">13</span> <span>External links</span> </div> </a> <ul id="toc-External_links-sublist" class="vector-toc-list"> </ul> </li> </ul> </div> </div> </nav> </div> </div> <div class="mw-content-container"> <main id="content" class="mw-body"> <header class="mw-body-header vector-page-titlebar"> <nav aria-label="Contents" class="vector-toc-landmark"> <div id="vector-page-titlebar-toc" class="vector-dropdown vector-page-titlebar-toc vector-button-flush-left" title="Table of Contents" > <input type="checkbox" id="vector-page-titlebar-toc-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-page-titlebar-toc" class="vector-dropdown-checkbox " aria-label="Toggle the table of contents" > <label id="vector-page-titlebar-toc-label" for="vector-page-titlebar-toc-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-listBullet mw-ui-icon-wikimedia-listBullet"></span> <span class="vector-dropdown-label-text">Toggle the table of contents</span> </label> <div class="vector-dropdown-content"> <div id="vector-page-titlebar-toc-unpinned-container" class="vector-unpinned-container"> </div> </div> </div> </nav> <h1 id="firstHeading" class="firstHeading mw-first-heading"><span class="mw-page-title-main">Altruism (biology)</span></h1> <div id="p-lang-btn" class="vector-dropdown mw-portlet mw-portlet-lang" > <input type="checkbox" id="p-lang-btn-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-p-lang-btn" class="vector-dropdown-checkbox mw-interlanguage-selector" aria-label="Go to an article in another language. Available in 10 languages" > <label id="p-lang-btn-label" for="p-lang-btn-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--action-progressive mw-portlet-lang-heading-10" aria-hidden="true" ><span class="vector-icon mw-ui-icon-language-progressive mw-ui-icon-wikimedia-language-progressive"></span> <span class="vector-dropdown-label-text">10 languages</span> </label> <div class="vector-dropdown-content"> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li class="interlanguage-link interwiki-es mw-list-item"><a href="https://es.wikipedia.org/wiki/Altruismo_biol%C3%B3gico" title="Altruismo biológico – Spanish" lang="es" hreflang="es" data-title="Altruismo biológico" data-language-autonym="Español" data-language-local-name="Spanish" class="interlanguage-link-target"><span>Español</span></a></li><li class="interlanguage-link interwiki-fa badge-Q17437798 badge-goodarticle mw-list-item" title="good article badge"><a href="https://fa.wikipedia.org/wiki/%D9%86%D9%88%D8%B9%E2%80%8C%D8%AF%D9%88%D8%B3%D8%AA%DB%8C_(%D8%B2%DB%8C%D8%B3%D8%AA%E2%80%8C%D8%B4%D9%86%D8%A7%D8%B3%DB%8C)" title="نوع‌دوستی (زیست‌شناسی) – Persian" lang="fa" hreflang="fa" data-title="نوع‌دوستی (زیست‌شناسی)" data-language-autonym="فارسی" data-language-local-name="Persian" class="interlanguage-link-target"><span>فارسی</span></a></li><li class="interlanguage-link interwiki-fr mw-list-item"><a href="https://fr.wikipedia.org/wiki/Altruisme_(biologie)" title="Altruisme (biologie) – French" lang="fr" hreflang="fr" data-title="Altruisme (biologie)" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-it mw-list-item"><a href="https://it.wikipedia.org/wiki/Altruismo_(biologia)" title="Altruismo (biologia) – Italian" lang="it" hreflang="it" data-title="Altruismo (biologia)" data-language-autonym="Italiano" data-language-local-name="Italian" class="interlanguage-link-target"><span>Italiano</span></a></li><li class="interlanguage-link interwiki-he mw-list-item"><a href="https://he.wikipedia.org/wiki/%D7%96%D7%95%D7%9C%D7%AA%D7%A0%D7%95%D7%AA_(%D7%91%D7%99%D7%95%D7%9C%D7%95%D7%92%D7%99%D7%94)" title="זולתנות (ביולוגיה) – Hebrew" lang="he" hreflang="he" data-title="זולתנות (ביולוגיה)" data-language-autonym="עברית" data-language-local-name="Hebrew" class="interlanguage-link-target"><span>עברית</span></a></li><li class="interlanguage-link interwiki-ja mw-list-item"><a href="https://ja.wikipedia.org/wiki/%E5%88%A9%E4%BB%96%E7%9A%84%E8%A1%8C%E5%8B%95" title="利他的行動 – Japanese" lang="ja" hreflang="ja" data-title="利他的行動" data-language-autonym="日本語" data-language-local-name="Japanese" class="interlanguage-link-target"><span>日本語</span></a></li><li class="interlanguage-link interwiki-ru mw-list-item"><a href="https://ru.wikipedia.org/wiki/%D0%90%D0%BB%D1%8C%D1%82%D1%80%D1%83%D0%B8%D0%B7%D0%BC_(%D0%B1%D0%B8%D0%BE%D0%BB%D0%BE%D0%B3%D0%B8%D1%87%D0%B5%D1%81%D0%BA%D0%B8%D0%B9)" title="Альтруизм (биологический) – Russian" lang="ru" hreflang="ru" data-title="Альтруизм (биологический)" data-language-autonym="Русский" data-language-local-name="Russian" class="interlanguage-link-target"><span>Русский</span></a></li><li class="interlanguage-link interwiki-sv mw-list-item"><a href="https://sv.wikipedia.org/wiki/Biologisk_altruism" title="Biologisk altruism – Swedish" lang="sv" hreflang="sv" data-title="Biologisk altruism" data-language-autonym="Svenska" data-language-local-name="Swedish" class="interlanguage-link-target"><span>Svenska</span></a></li><li class="interlanguage-link interwiki-uk mw-list-item"><a href="https://uk.wikipedia.org/wiki/%D0%90%D0%BB%D1%8C%D1%82%D1%80%D1%83%D1%97%D0%B7%D0%BC_%D1%83_%D1%82%D0%B2%D0%B0%D1%80%D0%B8%D0%BD" title="Альтруїзм у тварин – Ukrainian" lang="uk" hreflang="uk" data-title="Альтруїзм у тварин" data-language-autonym="Українська" data-language-local-name="Ukrainian" class="interlanguage-link-target"><span>Українська</span></a></li><li class="interlanguage-link interwiki-vi mw-list-item"><a href="https://vi.wikipedia.org/wiki/T%E1%BA%ADp_t%C3%ADnh_v%E1%BB%8B_tha" title="Tập tính vị tha – Vietnamese" lang="vi" hreflang="vi" data-title="Tập tính vị tha" data-language-autonym="Tiếng Việt" data-language-local-name="Vietnamese" class="interlanguage-link-target"><span>Tiếng Việt</span></a></li> </ul> <div class="after-portlet after-portlet-lang"><span class="wb-langlinks-edit wb-langlinks-link"><a href="https://www.wikidata.org/wiki/Special:EntityPage/Q2559380#sitelinks-wikipedia" title="Edit interlanguage links" class="wbc-editpage">Edit links</a></span></div> </div> </div> </div> </header> <div class="vector-page-toolbar"> <div class="vector-page-toolbar-container"> <div id="left-navigation"> <nav aria-label="Namespaces"> <div id="p-associated-pages" class="vector-menu vector-menu-tabs mw-portlet mw-portlet-associated-pages" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="ca-nstab-main" class="selected vector-tab-noicon mw-list-item"><a href="/wiki/Altruism_(biology)" title="View the content page [c]" accesskey="c"><span>Article</span></a></li><li id="ca-talk" class="vector-tab-noicon mw-list-item"><a href="/wiki/Talk:Altruism_(biology)" rel="discussion" title="Discuss improvements to the content page [t]" accesskey="t"><span>Talk</span></a></li> </ul> </div> </div> <div id="vector-variants-dropdown" class="vector-dropdown emptyPortlet" > <input type="checkbox" id="vector-variants-dropdown-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-variants-dropdown" class="vector-dropdown-checkbox " aria-label="Change language variant" > <label id="vector-variants-dropdown-label" for="vector-variants-dropdown-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet" aria-hidden="true" ><span class="vector-dropdown-label-text">English</span> </label> <div class="vector-dropdown-content"> <div id="p-variants" class="vector-menu mw-portlet mw-portlet-variants emptyPortlet" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> </ul> </div> </div> </div> </div> </nav> </div> <div id="right-navigation" class="vector-collapsible"> <nav aria-label="Views"> <div id="p-views" class="vector-menu vector-menu-tabs mw-portlet mw-portlet-views" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="ca-view" class="selected vector-tab-noicon mw-list-item"><a href="/wiki/Altruism_(biology)"><span>Read</span></a></li><li id="ca-edit" class="vector-tab-noicon mw-list-item"><a href="/w/index.php?title=Altruism_(biology)&action=edit" title="Edit this page [e]" accesskey="e"><span>Edit</span></a></li><li id="ca-history" class="vector-tab-noicon mw-list-item"><a href="/w/index.php?title=Altruism_(biology)&action=history" title="Past revisions of this page [h]" accesskey="h"><span>View history</span></a></li> </ul> </div> </div> </nav> <nav class="vector-page-tools-landmark" aria-label="Page tools"> <div id="vector-page-tools-dropdown" class="vector-dropdown vector-page-tools-dropdown" > <input type="checkbox" id="vector-page-tools-dropdown-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-page-tools-dropdown" class="vector-dropdown-checkbox " aria-label="Tools" > <label id="vector-page-tools-dropdown-label" for="vector-page-tools-dropdown-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet" aria-hidden="true" ><span class="vector-dropdown-label-text">Tools</span> </label> <div class="vector-dropdown-content"> <div id="vector-page-tools-unpinned-container" class="vector-unpinned-container"> <div id="vector-page-tools" class="vector-page-tools vector-pinnable-element"> <div class="vector-pinnable-header vector-page-tools-pinnable-header vector-pinnable-header-unpinned" data-feature-name="page-tools-pinned" data-pinnable-element-id="vector-page-tools" data-pinned-container-id="vector-page-tools-pinned-container" data-unpinned-container-id="vector-page-tools-unpinned-container" > <div class="vector-pinnable-header-label">Tools</div> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-pin-button" data-event-name="pinnable-header.vector-page-tools.pin">move to sidebar</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-page-tools.unpin">hide</button> </div> <div id="p-cactions" class="vector-menu mw-portlet mw-portlet-cactions emptyPortlet vector-has-collapsible-items" title="More options" > <div class="vector-menu-heading"> Actions </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="ca-more-view" class="selected vector-more-collapsible-item mw-list-item"><a href="/wiki/Altruism_(biology)"><span>Read</span></a></li><li id="ca-more-edit" class="vector-more-collapsible-item mw-list-item"><a href="/w/index.php?title=Altruism_(biology)&action=edit" title="Edit this page [e]" accesskey="e"><span>Edit</span></a></li><li id="ca-more-history" class="vector-more-collapsible-item mw-list-item"><a href="/w/index.php?title=Altruism_(biology)&action=history"><span>View history</span></a></li> </ul> </div> </div> <div id="p-tb" class="vector-menu mw-portlet mw-portlet-tb" > <div class="vector-menu-heading"> General </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="t-whatlinkshere" class="mw-list-item"><a href="/wiki/Special:WhatLinksHere/Altruism_(biology)" title="List of all English Wikipedia pages containing links to this page [j]" accesskey="j"><span>What links here</span></a></li><li id="t-recentchangeslinked" class="mw-list-item"><a href="/wiki/Special:RecentChangesLinked/Altruism_(biology)" rel="nofollow" title="Recent changes in pages linked from this page [k]" accesskey="k"><span>Related changes</span></a></li><li id="t-upload" class="mw-list-item"><a href="//en.wikipedia.org/wiki/Wikipedia:File_Upload_Wizard" title="Upload files [u]" accesskey="u"><span>Upload file</span></a></li><li id="t-permalink" class="mw-list-item"><a href="/w/index.php?title=Altruism_(biology)&oldid=1282159263" title="Permanent link to this revision of this page"><span>Permanent link</span></a></li><li id="t-info" class="mw-list-item"><a href="/w/index.php?title=Altruism_(biology)&action=info" title="More information about this page"><span>Page information</span></a></li><li id="t-cite" class="mw-list-item"><a href="/w/index.php?title=Special:CiteThisPage&page=Altruism_%28biology%29&id=1282159263&wpFormIdentifier=titleform" title="Information on how to cite this page"><span>Cite this page</span></a></li><li id="t-urlshortener" class="mw-list-item"><a href="/w/index.php?title=Special:UrlShortener&url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FAltruism_%28biology%29"><span>Get shortened URL</span></a></li><li id="t-urlshortener-qrcode" class="mw-list-item"><a href="/w/index.php?title=Special:QrCode&url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FAltruism_%28biology%29"><span>Download QR code</span></a></li> </ul> </div> </div> <div id="p-coll-print_export" class="vector-menu mw-portlet mw-portlet-coll-print_export" > <div class="vector-menu-heading"> Print/export </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="coll-download-as-rl" class="mw-list-item"><a href="/w/index.php?title=Special:DownloadAsPdf&page=Altruism_%28biology%29&action=show-download-screen" title="Download this page as a PDF file"><span>Download as PDF</span></a></li><li id="t-print" class="mw-list-item"><a href="/w/index.php?title=Altruism_(biology)&printable=yes" title="Printable version of this page [p]" accesskey="p"><span>Printable version</span></a></li> </ul> </div> </div> <div id="p-wikibase-otherprojects" class="vector-menu mw-portlet mw-portlet-wikibase-otherprojects" > <div class="vector-menu-heading"> In other projects </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="t-wikibase" class="wb-otherproject-link wb-otherproject-wikibase-dataitem mw-list-item"><a href="https://www.wikidata.org/wiki/Special:EntityPage/Q2559380" title="Structured data on this page hosted by Wikidata [g]" accesskey="g"><span>Wikidata item</span></a></li> </ul> </div> </div> </div> </div> </div> </div> </nav> </div> </div> </div> <div class="vector-column-end"> <div class="vector-sticky-pinned-container"> <nav class="vector-page-tools-landmark" aria-label="Page tools"> <div id="vector-page-tools-pinned-container" class="vector-pinned-container"> </div> </nav> <nav class="vector-appearance-landmark" aria-label="Appearance"> <div id="vector-appearance-pinned-container" class="vector-pinned-container"> <div id="vector-appearance" class="vector-appearance vector-pinnable-element"> <div class="vector-pinnable-header vector-appearance-pinnable-header vector-pinnable-header-pinned" data-feature-name="appearance-pinned" data-pinnable-element-id="vector-appearance" data-pinned-container-id="vector-appearance-pinned-container" data-unpinned-container-id="vector-appearance-unpinned-container" > <div class="vector-pinnable-header-label">Appearance</div> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-pin-button" data-event-name="pinnable-header.vector-appearance.pin">move to sidebar</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-appearance.unpin">hide</button> </div> </div> </div> </nav> </div> </div> <div id="bodyContent" class="vector-body" aria-labelledby="firstHeading" data-mw-ve-target-container> <div class="vector-body-before-content"> <div class="mw-indicators"> </div> <div id="siteSub" class="noprint">From Wikipedia, the free encyclopedia</div> </div> <div id="contentSub"><div id="mw-content-subtitle"></div></div> <div id="mw-content-text" class="mw-body-content"><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none">Behaviour that increases the fitness of another while decreasing the fitness of self</div> <p class="mw-empty-elt"> </p> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Grooming_monkeys.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/b/b5/Grooming_monkeys.jpg/250px-Grooming_monkeys.jpg" decoding="async" width="220" height="157" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/b5/Grooming_monkeys.jpg/330px-Grooming_monkeys.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/b5/Grooming_monkeys.jpg/500px-Grooming_monkeys.jpg 2x" data-file-width="1832" data-file-height="1304" /></a><figcaption>Olive baboons grooming</figcaption></figure> <p>In <a href="/wiki/Biology" title="Biology">biology</a>, <b>altruism</b> refers to behaviour by an individual that increases the <a href="/wiki/Fitness_(biology)" title="Fitness (biology)">fitness</a> of another individual while decreasing their own.<sup id="cite_ref-Bell_2008_1-0" class="reference"><a href="#cite_note-Bell_2008-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> Altruism in this sense is different from the philosophical concept of altruism, in which an action would only be called "altruistic" if it was done with the conscious intention of helping another. In the behavioural sense, there is no such requirement. As such, it is not evaluated in moral terms—it is the consequences of an action for reproductive fitness that determine whether the action is considered altruistic, not the intentions, if any, with which the action is performed.<sup id="cite_ref-Okasha_2008_2-0" class="reference"><a href="#cite_note-Okasha_2008-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> </p><p>The term <i>altruism</i> was coined by the French philosopher <a href="/wiki/Auguste_Comte" title="Auguste Comte">Auguste Comte</a> in French, as <i>altruisme</i>, for an <a href="/wiki/Antonym" class="mw-redirect" title="Antonym">antonym</a> of egoism.<sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> He derived it from the Italian <i>altrui</i>, which in turn was derived from Latin <i>alteri</i>, meaning "other people" or "somebody else".<sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> </p><p>Altruistic behaviours appear most obviously in <a href="/wiki/Kin_selection" title="Kin selection">kin relationships</a>, such as in parenting, but may also be evident among wider social groups, such as in social insects. They allow an individual to increase the success of its genes by helping relatives that share those genes.<sup id="cite_ref-Davies_2012_6-0" class="reference"><a href="#cite_note-Davies_2012-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> Obligate altruism is the permanent loss of direct fitness (with potential for indirect fitness gain).<sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> For example, honey bee workers may forage for the colony. Facultative altruism is temporary loss of direct fitness (with potential for indirect fitness gain followed by personal reproduction). For example, a <a href="/wiki/Florida_scrub_jay" title="Florida scrub jay">Florida scrub jay</a> may help at the nest, then gain parental territory.<sup id="cite_ref-8" class="reference"><a href="#cite_note-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Overview">Overview</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Altruism_(biology)&action=edit&section=1" title="Edit section: Overview"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>In <a href="/wiki/Ethology" title="Ethology">ethology</a> (the study of behavior), and more generally in the study of <a href="/wiki/Evolution_of_eusociality" title="Evolution of eusociality">social evolution</a>, on occasion, some animals do behave in ways that reduce their individual fitness but increase the fitness of other individuals in the population; this is a functional definition of altruism.<sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> Research in <a href="/wiki/Evolutionary_theory" class="mw-redirect" title="Evolutionary theory">evolutionary theory</a> has been applied to social behaviour, including altruism. Cases of animals helping individuals to whom they are closely related can be explained by <a href="/wiki/Kin_selection" title="Kin selection">kin selection</a>, and are not considered true altruism. Beyond the physical exertions that in some species mothers and in some species fathers undertake to protect their young, extreme examples of sacrifice may occur. One example is <a href="/wiki/Matriphagy" title="Matriphagy">matriphagy</a> (the consumption of the mother by her offspring) in the spider <i><a href="/wiki/Stegodyphus" title="Stegodyphus">Stegodyphus</a></i>; another example is a male spider allowing a female fertilized by him to eat him. <a href="/wiki/Hamilton%27s_rule" class="mw-redirect" title="Hamilton's rule">Hamilton's rule</a> describes the benefit of such altruism in terms of <a href="/wiki/Sewall_Wright" title="Sewall Wright">Wright's</a> <a href="/wiki/Coefficient_of_relationship" title="Coefficient of relationship">coefficient of relationship</a> to the beneficiary and the benefit granted to the beneficiary minus the cost to the sacrificer. Should this sum be greater than zero a fitness gain will result from the sacrifice. </p><p>When apparent altruism is not between kin, it may be based on <a href="/wiki/Reciprocal_altruism" title="Reciprocal altruism">reciprocity</a>. A monkey will present its back to another monkey, who will pick out parasites; after a time the roles will be reversed. Such reciprocity will pay off, in evolutionary terms, as long as the costs of helping are less than the benefits of being helped and as long as animals will not gain in the long run by "cheating"—that is to say, by receiving favours without returning them. This is elaborated on in <a href="/wiki/Evolutionary_game_theory" title="Evolutionary game theory">evolutionary game theory</a> and specifically the <a href="/wiki/Prisoner%27s_dilemma" title="Prisoner's dilemma">prisoner's dilemma</a> as social theory. </p> <div class="mw-heading mw-heading2"><h2 id="Implications_in_evolutionary_theory">Implications in evolutionary theory</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Altruism_(biology)&action=edit&section=2" title="Edit section: Implications in evolutionary theory"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Canis_lupus_pack_surrounding_Bison.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/4/45/Canis_lupus_pack_surrounding_Bison.jpg/250px-Canis_lupus_pack_surrounding_Bison.jpg" decoding="async" width="250" height="202" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/4/45/Canis_lupus_pack_surrounding_Bison.jpg/500px-Canis_lupus_pack_surrounding_Bison.jpg 1.5x" data-file-width="599" data-file-height="484" /></a><figcaption>Cooperative hunting by wolves allows them to tackle much larger and more nutritious prey than any individual wolf could handle. However, such cooperation could, potentially, be exploited by selfish individuals who do not expose themselves to the dangers of the hunt, but nevertheless share in the spoils.</figcaption></figure> <p>The existence of altruism in nature is at first sight puzzling, because altruistic behaviour reduces the likelihood that an individual will reproduce. The idea that <i><a href="/wiki/Group_selection" title="Group selection">group selection</a></i> might explain the evolution of altruism was first broached by Darwin himself in <a href="/wiki/The_Descent_of_Man,_and_Selection_in_Relation_to_Sex" title="The Descent of Man, and Selection in Relation to Sex">The Descent of Man, and Selection in Relation to Sex</a>, (1871). The concept of group selection has had a chequered and controversial history in evolutionary biology but the uncritical 'good of the species' tradition came to an abrupt halt in the 1960s, due largely to the work of <a href="/wiki/George_C._Williams_(biologist)" class="mw-redirect" title="George C. Williams (biologist)">George C. Williams</a>,<sup id="cite_ref-10" class="reference"><a href="#cite_note-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> and <a href="/wiki/John_Maynard_Smith" title="John Maynard Smith">John Maynard Smith</a><sup id="cite_ref-11" class="reference"><a href="#cite_note-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> as well as <a href="/wiki/Richard_Dawkins" title="Richard Dawkins">Richard Dawkins</a>.<sup id="cite_ref-River_Out_of_Eden_12-0" class="reference"><a href="#cite_note-River_Out_of_Eden-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-13" class="reference"><a href="#cite_note-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-14" class="reference"><a href="#cite_note-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-15" class="reference"><a href="#cite_note-15"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup> These evolutionary theorists pointed out that <a href="/wiki/Natural_selection" title="Natural selection">natural selection</a> acts on the individual, and that it is the individual's fitness (number of offspring and grand-offspring produced compared to the rest of the population) that drives evolution. A group advantage (e.g. hunting in a pack) that is disadvantageous to the individual (who might be harmed during the hunt, when it could avoid injury by hanging back from the pack but still share in the spoils) cannot evolve, because the selfish individual will leave, on average, more offspring than those who join the pack and suffer injuries as a result. If the selfishness is hereditary, this will ultimately result in the population consisting entirely of selfish individuals. However, in the 1960s and 1970s an alternative to the "group selection" theory emerged. This was the <a href="/wiki/Kin_selection" title="Kin selection">kin selection</a> theory, due originally to <a href="/wiki/W._D._Hamilton" title="W. D. Hamilton">W. D. Hamilton</a>.<sup id="cite_ref-Hamilton_1964_16-0" class="reference"><a href="#cite_note-Hamilton_1964-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup> Kin selection is an instance of <a href="/wiki/Inclusive_fitness" title="Inclusive fitness">inclusive fitness</a>, which is based on the notion that an individual shares only half its genes with each offspring, but also with each full <a href="/wiki/Sib_(anthropology)" title="Sib (anthropology)">sibling</a> (See footnote<sup id="cite_ref-19" class="reference"><a href="#cite_note-19"><span class="cite-bracket">[</span>nb 1<span class="cite-bracket">]</span></a></sup>). From an evolutionary genetic point of view it is therefore as advantageous to help with the upbringing of full sibs as it is to produce and raise one's own offspring. The two activities are evolutionarily entirely equivalent. Co-operative breeding (i.e. helping one's parents raise sibs—provided they are full sibs) could thus evolve without the need for group-level selection. This quickly gained prominence among biologists interested in the evolution of social behaviour.<sup id="cite_ref-Okasha_2008_2-1" class="reference"><a href="#cite_note-Okasha_2008-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> </p><p>In 1971 <a href="/wiki/Robert_Trivers" title="Robert Trivers">Robert Trivers</a><sup id="cite_ref-20" class="reference"><a href="#cite_note-20"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup> introduced his <a href="/wiki/Reciprocal_altruism" title="Reciprocal altruism">reciprocal altruism</a> theory to explain the evolution of helping at the nest of an unrelated breeding pair of birds. He argued that an individual might act as a helper if there was a high probabilistic expectation of being helped by the recipients at some later date. If, however, the recipients did not reciprocate when it was possible to do so, the altruistic interaction with these recipients would be permanently terminated. But if the recipients did not cheat then the reciprocal altruism would continue indefinitely to both parties' advantage.<sup id="cite_ref-21" class="reference"><a href="#cite_note-21"><span class="cite-bracket">[</span>20<span class="cite-bracket">]</span></a></sup> This model was considered by many (e.g. West-Eberhard<sup id="cite_ref-22" class="reference"><a href="#cite_note-22"><span class="cite-bracket">[</span>21<span class="cite-bracket">]</span></a></sup> and Dawkins<sup id="cite_ref-23" class="reference"><a href="#cite_note-23"><span class="cite-bracket">[</span>22<span class="cite-bracket">]</span></a></sup>) to be <a href="/wiki/Evolutionarily_stable_strategy" title="Evolutionarily stable strategy">evolutionarily unstable</a> because it is prone to invasion by cheats for the same reason that cooperative hunting can be invaded and replaced by cheats. However, Trivers did make reference to the <a href="/w/index.php?title=Prisoner%27s_dilemma_game&action=edit&redlink=1" class="new" title="Prisoner's dilemma game (page does not exist)">prisoner's dilemma game</a> which, 10 years later, would restore interest in Trivers' reciprocal altruism theory, but under the title of "tit-for-tat".<sup id="cite_ref-Axelrod_1989_24-0" class="reference"><a href="#cite_note-Axelrod_1989-24"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup> </p><p>In its original form the Prisoner's Dilemma Game (PDG) described two awaiting trial prisoners, A and B, each faced with the choice of betraying the other or remaining silent. The "<a href="/wiki/Game_theory" title="Game theory">game</a>" has four possible outcomes: (a) they both betray each other, and are both sentenced to two years in prison; (b) A betrays B, which sets A free and B is sentenced to four years in prison; (c) B betrays A, with the same result as (b) except that it is B who is set free and the other spends four years in jail; (d) both remain silent, resulting in a six-month sentence each. Clearly (d) ("cooperation") is the best mutual strategy, but from the point of view of the individual betrayal is unbeatable (resulting in being set free, or getting only a two-year sentence). Remaining silent results in a four-year or six-month sentence. This is exemplified by a further example of the PDG: two strangers attend a restaurant together and decide to split the bill. The mutually best ploy would be for both parties to order the cheapest items on the menu (mutual cooperation). But if one member of the party exploits the situation by ordering the most expensive items, then it is best for the other member to do likewise. In fact, if the fellow diner's personality is completely unknown, and the two diners are unlikely ever to meet again, it is always in one's own best interests to eat as expensively as possible. Situations in nature that are subject to the same dynamics (rewards and penalties) as the PDG define cooperative behaviour: it is never in the individual's fitness interests to cooperate, even though mutual cooperation rewards the two contestants (together) more highly than any other strategy.<sup id="cite_ref-Sigmund_1993_25-0" class="reference"><a href="#cite_note-Sigmund_1993-25"><span class="cite-bracket">[</span>24<span class="cite-bracket">]</span></a></sup> Cooperation cannot evolve under these circumstances. </p><p>However, in 1981 Axelrod and Hamilton<sup id="cite_ref-Axelrod_1989_24-1" class="reference"><a href="#cite_note-Axelrod_1989-24"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup> noted that if the same contestants in the PDG meet repeatedly (the so-called Iterated Prisoner's Dilemma game, IPD) then tit-for-tat (foreshadowed by Robert Triver's reciprocal altruism theory) is a robust strategy which promotes altruism.<sup id="cite_ref-Axelrod_1989_24-2" class="reference"><a href="#cite_note-Axelrod_1989-24"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Sigmund_1993_25-1" class="reference"><a href="#cite_note-Sigmund_1993-25"><span class="cite-bracket">[</span>24<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-26" class="reference"><a href="#cite_note-26"><span class="cite-bracket">[</span>25<span class="cite-bracket">]</span></a></sup> In "tit-for-tat" both players' opening moves are cooperation. Thereafter each contestant repeats the other player's last move, resulting in a seemingly endless sequence of mutually cooperative moves. However, mistakes severely undermine tit-for-tat's effectiveness, giving rise to prolonged sequences of betrayal, which can only be rectified by another mistake. Since these initial discoveries, all the other possible IPD game strategies have been identified (16 possibilities in all, including, for instance, "generous tit-for-tat", which behaves like "tit-for-tat", except that it cooperates with a small probability when the opponent's last move was "betray".<sup id="cite_ref-27" class="reference"><a href="#cite_note-27"><span class="cite-bracket">[</span>26<span class="cite-bracket">]</span></a></sup>), but all can be outperformed by at least one of the other strategies, should one of the players switch to such a strategy. The result is that none is <a href="/wiki/Evolutionarily_stable_strategy" title="Evolutionarily stable strategy">evolutionarily stable</a>, and any prolonged series of the iterated prisoner's dilemma game, in which alternative strategies arise at random, gives rise to a chaotic sequence of strategy changes that never ends.<sup id="cite_ref-Sigmund_1993_25-2" class="reference"><a href="#cite_note-Sigmund_1993-25"><span class="cite-bracket">[</span>24<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-28" class="reference"><a href="#cite_note-28"><span class="cite-bracket">[</span>27<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Koeslag_1997_29-0" class="reference"><a href="#cite_note-Koeslag_1997-29"><span class="cite-bracket">[</span>28<span class="cite-bracket">]</span></a></sup> </p> <style data-mw-deduplicate="TemplateStyles:r1273380762/mw-parser-output/.tmulti">.mw-parser-output .tmulti .multiimageinner{display:flex;flex-direction:column}.mw-parser-output .tmulti .trow{display:flex;flex-direction:row;clear:left;flex-wrap:wrap;width:100%;box-sizing:border-box}.mw-parser-output .tmulti .tsingle{margin:1px;float:left}.mw-parser-output .tmulti .theader{clear:both;font-weight:bold;text-align:center;align-self:center;background-color:transparent;width:100%}.mw-parser-output .tmulti .thumbcaption{background-color:transparent}.mw-parser-output .tmulti .text-align-left{text-align:left}.mw-parser-output .tmulti .text-align-right{text-align:right}.mw-parser-output .tmulti .text-align-center{text-align:center}@media all and (max-width:720px){.mw-parser-output .tmulti .thumbinner{width:100%!important;box-sizing:border-box;max-width:none!important;align-items:center}.mw-parser-output .tmulti .trow{justify-content:center}.mw-parser-output .tmulti .tsingle{float:none!important;max-width:100%!important;box-sizing:border-box;text-align:center}.mw-parser-output .tmulti .tsingle .thumbcaption{text-align:left}.mw-parser-output .tmulti .trow>.thumbcaption{text-align:center}}@media screen{html.skin-theme-clientpref-night .mw-parser-output .tmulti .multiimageinner span:not(.skin-invert-image):not(.skin-invert):not(.bg-transparent) img{background-color:white}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .tmulti .multiimageinner span:not(.skin-invert-image):not(.skin-invert):not(.bg-transparent) img{background-color:white}}</style><div class="thumb tmulti tright"><div class="thumbinner multiimageinner" style="width:618px;max-width:618px"><div class="trow"><div class="theader">The handicap principle</div></div><div class="trow"><div class="tsingle" style="width:232px;max-width:232px"><div class="thumbimage"><span typeof="mw:File"><a href="/wiki/File:Paonroue.JPG" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/0/05/Paonroue.JPG/230px-Paonroue.JPG" decoding="async" width="230" height="173" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/0/05/Paonroue.JPG/345px-Paonroue.JPG 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/0/05/Paonroue.JPG/460px-Paonroue.JPG 2x" data-file-width="2048" data-file-height="1536" /></a></span></div><div class="thumbcaption">A male peacock with its beautiful but clumsy, aerodynamically unsound tail—a handicap, comparable to a race horse's handicap.</div></div><div class="tsingle" style="width:382px;max-width:382px"><div class="thumbimage"><span typeof="mw:File"><a href="/wiki/File:Curlin_in_the_Final_Turn_in_the_2008_Stephen_Foster_Handicap_(2972085393).jpg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/b/b7/Curlin_in_the_Final_Turn_in_the_2008_Stephen_Foster_Handicap_%282972085393%29.jpg/380px-Curlin_in_the_Final_Turn_in_the_2008_Stephen_Foster_Handicap_%282972085393%29.jpg" decoding="async" width="380" height="173" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/b/b7/Curlin_in_the_Final_Turn_in_the_2008_Stephen_Foster_Handicap_%282972085393%29.jpg/570px-Curlin_in_the_Final_Turn_in_the_2008_Stephen_Foster_Handicap_%282972085393%29.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/b/b7/Curlin_in_the_Final_Turn_in_the_2008_Stephen_Foster_Handicap_%282972085393%29.jpg/760px-Curlin_in_the_Final_Turn_in_the_2008_Stephen_Foster_Handicap_%282972085393%29.jpg 2x" data-file-width="887" data-file-height="404" /></a></span></div><div class="thumbcaption">The best horses in a <a href="/wiki/Handicap_(horse_racing)" title="Handicap (horse racing)">handicap race</a> carry the largest weights, so the size of the handicap is a measure of the animal's quality</div></div></div></div></div> <p>In the light of the Iterated Prisoner's Dilemma Game failing to provide a full answer to the evolution of cooperation or altruism, several alternative explanations have been proposed. </p><p>There are striking parallels between altruistic acts and exaggerated <a href="/wiki/Sexual_selection" title="Sexual selection">sexual ornaments</a> displayed by some animals, particularly certain bird species, such as, amongst others, the <a href="/wiki/Peafowl" title="Peafowl">peacock</a>. Both are costly in fitness terms, and both are generally conspicuous to other members of the population or species. This led <a href="/wiki/Amotz_Zahavi" title="Amotz Zahavi">Amotz Zahavi</a> to suggest that both might be <a href="/wiki/Signalling_theory" title="Signalling theory">fitness signals</a> rendered evolutionarily stable by his <a href="/wiki/Handicap_principle" title="Handicap principle">handicap principle</a>.<sup id="cite_ref-30" class="reference"><a href="#cite_note-30"><span class="cite-bracket">[</span>29<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Zahavi_1997_31-0" class="reference"><a href="#cite_note-Zahavi_1997-31"><span class="cite-bracket">[</span>30<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-32" class="reference"><a href="#cite_note-32"><span class="cite-bracket">[</span>31<span class="cite-bracket">]</span></a></sup> If a signal is to remain reliable, and generally resistant to falsification, <a href="/wiki/Signalling_theory#Sports_handicapping_metaphor" title="Signalling theory">the signal</a> has to be evolutionarily costly.<sup id="cite_ref-33" class="reference"><a href="#cite_note-33"><span class="cite-bracket">[</span>32<span class="cite-bracket">]</span></a></sup> Thus, if a (low fitness) liar were to use the highly costly signal, which seriously eroded its real fitness, it would find it difficult to maintain a semblance of normality.<sup id="cite_ref-34" class="reference"><a href="#cite_note-34"><span class="cite-bracket">[</span>33<span class="cite-bracket">]</span></a></sup> Zahavi borrowed the term "handicap principle" from sports handicapping systems. These systems are aimed at reducing disparities in performance, thereby making the outcome of contests less predictable. In a horse <a href="/wiki/Handicap_(horse_racing)" title="Handicap (horse racing)">handicap race</a>, provenly faster horses are given heavier weights to carry under their saddles than inherently slower horses. Similarly, in <a href="/wiki/Golf_handicap" class="mw-redirect" title="Golf handicap">amateur golf</a>, better golfers have fewer strokes subtracted from their raw scores than the less talented players. The handicap therefore correlates with unhandicapped performance, making it possible, if one knows nothing about the horses, to predict which unhandicapped horse would win an open race. It would be the one handicapped with the greatest weight in the saddle. The handicaps in nature are highly visible, and therefore a peahen, for instance, would be able to deduce the health of a potential mate by comparing its handicap (the size of the peacock's tail) with those of the other males. The loss of the male's fitness caused by the handicap is offset by its increased access to females, which is as much of a fitness concern as is its health. An altruistic act is, by definition, similarly costly. It would therefore also signal fitness, and is probably as attractive to females as a physical handicap. If this is the case altruism is evolutionarily stabilized by <a href="/wiki/Sexual_selection" title="Sexual selection">sexual selection</a>.<sup id="cite_ref-Zahavi_1997_31-1" class="reference"><a href="#cite_note-Zahavi_1997-31"><span class="cite-bracket">[</span>30<span class="cite-bracket">]</span></a></sup> </p> <figure class="mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Flickr_-_Rainbirder_-_African_pygmy-kingfisher_(Ceyx_pictus).jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Flickr_-_Rainbirder_-_African_pygmy-kingfisher_%28Ceyx_pictus%29.jpg/330px-Flickr_-_Rainbirder_-_African_pygmy-kingfisher_%28Ceyx_pictus%29.jpg" decoding="async" width="270" height="176" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Flickr_-_Rainbirder_-_African_pygmy-kingfisher_%28Ceyx_pictus%29.jpg/500px-Flickr_-_Rainbirder_-_African_pygmy-kingfisher_%28Ceyx_pictus%29.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Flickr_-_Rainbirder_-_African_pygmy-kingfisher_%28Ceyx_pictus%29.jpg/540px-Flickr_-_Rainbirder_-_African_pygmy-kingfisher_%28Ceyx_pictus%29.jpg 2x" data-file-width="800" data-file-height="522" /></a><figcaption><a href="/wiki/African_pygmy_kingfisher" title="African pygmy kingfisher">African pygmy kingfisher</a>, showing details of appearance and colouration that are shared by all African pygmy kingfishers to a high degree of fidelity.<sup id="cite_ref-35" class="reference"><a href="#cite_note-35"><span class="cite-bracket">[</span>34<span class="cite-bracket">]</span></a></sup></figcaption></figure> <p>There is an alternate strategy for identifying fit mates which does not rely on one gender having exaggerated sexual ornaments or other handicaps, but is generally applicable to most, if not all sexual creatures. It derives from the concept that the change in appearance and functionality caused by a <a href="/wiki/Silent_mutation" title="Silent mutation">non-silent</a> <a href="/wiki/Mutation" title="Mutation">mutation</a> will generally stand out in a population. This is because that altered appearance and functionality will be unusual, peculiar, and different from the norm within that population. The norm against which these unusual features are judged is made up of fit attributes that have attained their plurality through <a href="/wiki/Natural_selection" title="Natural selection">natural selection</a>, while less adaptive attributes will be in the minority or frankly rare.<sup id="cite_ref-Fisher_1930_36-0" class="reference"><a href="#cite_note-Fisher_1930-36"><span class="cite-bracket">[</span>35<span class="cite-bracket">]</span></a></sup> Since the overwhelming majority of mutant features are maladaptive, and it is impossible to predict evolution's future direction, sexual creatures would be expected to <a href="/wiki/Koinophilia" title="Koinophilia">prefer mates with the fewest unusual or minority features</a>.<sup id="cite_ref-Fisher_1930_36-1" class="reference"><a href="#cite_note-Fisher_1930-36"><span class="cite-bracket">[</span>35<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-37" class="reference"><a href="#cite_note-37"><span class="cite-bracket">[</span>36<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Langlois_1990_38-0" class="reference"><a href="#cite_note-Langlois_1990-38"><span class="cite-bracket">[</span>37<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Koeslag_1990_39-0" class="reference"><a href="#cite_note-Koeslag_1990-39"><span class="cite-bracket">[</span>38<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Poelstra_2014_40-0" class="reference"><a href="#cite_note-Poelstra_2014-40"><span class="cite-bracket">[</span>39<span class="cite-bracket">]</span></a></sup> This will have the effect of a sexual population rapidly shedding peripheral phenotypic features and canalizing the entire outward appearance and behaviour so that all the members of that population will begin to look remarkably similar in every detail, as illustrated in the accompanying photograph of the <a href="/wiki/African_pygmy_kingfisher" title="African pygmy kingfisher">African pygmy kingfisher</a>, <i>Ispidina picta</i>. Once a population has become as homogeneous in appearance as is typical of most species, its entire repertoire of behaviours will also be rendered <a href="/wiki/Evolutionarily_stable_strategy" title="Evolutionarily stable strategy">evolutionarily stable</a>, including any altruistic, cooperative and social characteristics. Thus, in the example of the selfish individual who hangs back from the rest of the hunting pack, but who nevertheless joins in the spoils, that individual will be recognized as being different from the norm, and will therefore find it difficult to attract a mate.<sup id="cite_ref-Koeslag_1990_39-1" class="reference"><a href="#cite_note-Koeslag_1990-39"><span class="cite-bracket">[</span>38<span class="cite-bracket">]</span></a></sup> Its genes will therefore have only a very small probability of being passed on to the next generation, thus evolutionarily stabilizing cooperation and social interactions at whatever level of complexity is the norm in that population.<sup id="cite_ref-Koeslag_1997_29-1" class="reference"><a href="#cite_note-Koeslag_1997-29"><span class="cite-bracket">[</span>28<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Koeslag_2003_41-0" class="reference"><a href="#cite_note-Koeslag_2003-41"><span class="cite-bracket">[</span>40<span class="cite-bracket">]</span></a></sup> </p><p>Contrary to the mainstream dogma, a recently published article .<sup id="cite_ref-42" class="reference"><a href="#cite_note-42"><span class="cite-bracket">[</span>41<span class="cite-bracket">]</span></a></sup> using agent-based models demonstrates that several crucial mechanisms, such as kin selection, punishment, multilevel selection, and spatial structure, cannot rescue the evolution of cooperation. The new findings revive a long-standing puzzle in the evolution theory. In addition, the work has potential therapeutic benefits for numerous incurable diseases </p> <div class="mw-heading mw-heading2"><h2 id="Reciprocity_mechanisms">Reciprocity mechanisms</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Altruism_(biology)&action=edit&section=3" title="Edit section: Reciprocity mechanisms"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Altruism in animals describes a range of behaviors performed by animals that may be to their own disadvantage but which benefit others.<sup id="cite_ref-43" class="reference"><a href="#cite_note-43"><span class="cite-bracket">[</span>42<span class="cite-bracket">]</span></a></sup> The costs and benefits are measured in terms of reproductive fitness, or expected number of offspring. So by behaving altruistically, an organism reduces the number of offspring it is likely to produce itself, but boosts the likelihood that other organisms are to produce offspring. There are other forms of altruism in nature other than risk-taking behavior, such as reciprocal altruism. This biological notion of altruism is not identical to the everyday human concept. For humans, an action would only be called 'altruistic' if it was done with the conscious intention of helping another. Yet in the biological sense there is no such requirement. Instead, until we can communicate directly with other species, an accurate theory to describe altruistic acts between species is Biological Market Theory. Humans and other animals exchange benefits in several ways, known technically as reciprocity mechanism. No matter what the mechanism, the common thread is that benefits find their way back to the original giver. </p> <div class="mw-heading mw-heading3"><h3 id="Symmetry-based">Symmetry-based</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Altruism_(biology)&action=edit&section=4" title="Edit section: Symmetry-based"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Also known as the "buddy-system", mutual affection between two parties prompts similar behavior in both directions without need to track of daily give-and-take, so long as the overall relationship remains satisfactory. This is one of the most common mechanisms of reciprocity in nature, this kind is present in humans, primates, and many other mammals. </p> <div class="mw-heading mw-heading3"><h3 id="Attitudinal">Attitudinal</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Altruism_(biology)&action=edit&section=5" title="Edit section: Attitudinal"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Also known as, "If you're nice, I'll be nice too." This mechanism of reciprocity is similar to the heuristic of the golden rule, "Treat others how you would like to be treated." Parties mirror one another's attitudes, exchanging favors on the spot. Instant attitudinal reciprocity occurs among monkeys, and people often rely on it with strangers and acquaintances. </p> <div class="mw-heading mw-heading3"><h3 id="Calculated">Calculated</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Altruism_(biology)&action=edit&section=6" title="Edit section: Calculated"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Also known as, "what have you done for me lately?" Individuals keep track of the benefits they exchange with particular partners, which helps them decide to whom to return favors. This mechanism is typical of chimpanzees and very common among human relationships.<sup id="cite_ref-pmid15915815_44-0" class="reference"><a href="#cite_note-pmid15915815-44"><span class="cite-bracket">[</span>43<span class="cite-bracket">]</span></a></sup> Yet some opposing experimental research suggests that calculated or contingent reciprocity does not spontaneously arise in laboratory experimental settings, despite patterns of behavior. </p> <div class="mw-heading mw-heading2"><h2 id="Biological_market_theory">Biological market theory</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Altruism_(biology)&action=edit&section=7" title="Edit section: Biological market theory"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Biological market theory is an extension of the idea of reciprocal altruism, as a mechanism to explain altruistic acts between unrelated individuals in a more flexible system of exchanging commodities. The term 'biological market' was first used by Ronald Noe and Hammerstein in 1994 to refer to all the interactions between organisms in which different organisms function as 'traders' that exchange goods and services such as food and water, grooming, warning calls, shelter, etc. Biological market theory consists of five formal characteristics which present a basis for altruism. </p> <ol><li>Commodities are exchanged between individuals that differ in the degree of control over those commodities.</li> <li>Trading partners are chosen from a number of potential partners.</li> <li>There is competition among the members of the chosen class to be the most attractive partner. This competition by 'outbidding' causes an increase in the value of the commodity offered.</li> <li>Supply and demand determine the bartering value of commodities exchanged.</li> <li>Commodities on offer can be advertised. As in commercial advertisements there is a potential for false information.<sup id="cite_ref-45" class="reference"><a href="#cite_note-45"><span class="cite-bracket">[</span>44<span class="cite-bracket">]</span></a></sup></li></ol> <figure class="mw-default-size mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Epinephelus_tukula_is_cleaned_by_two_Labroides_dimidiatus.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/4/45/Epinephelus_tukula_is_cleaned_by_two_Labroides_dimidiatus.jpg/250px-Epinephelus_tukula_is_cleaned_by_two_Labroides_dimidiatus.jpg" decoding="async" width="220" height="165" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/4/45/Epinephelus_tukula_is_cleaned_by_two_Labroides_dimidiatus.jpg/330px-Epinephelus_tukula_is_cleaned_by_two_Labroides_dimidiatus.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/4/45/Epinephelus_tukula_is_cleaned_by_two_Labroides_dimidiatus.jpg/500px-Epinephelus_tukula_is_cleaned_by_two_Labroides_dimidiatus.jpg 2x" data-file-width="1024" data-file-height="768" /></a><figcaption><div class="center">Two <a href="/wiki/Bluestreak_cleaner_wrasse" title="Bluestreak cleaner wrasse">bluestreak cleaner wrasses</a> cleaning a <a href="/wiki/Potato_cod" class="mw-redirect" title="Potato cod">potato cod</a></div></figcaption></figure> <p>The applicability of biological market theory with its emphasis on partner choice is evident in the interactions between the <a href="/wiki/Cleaner_wrasse" class="mw-redirect" title="Cleaner wrasse">cleaner wrasse</a> and its "client" <a href="/wiki/Reef_fish" class="mw-redirect" title="Reef fish">reef fish</a>. <a href="/wiki/Cleaner_fish" title="Cleaner fish">Cleaners</a> have small territories, which the majority of reef fish species actively visit to invite inspection of their surface, gills, and mouth. Clients benefit from the removal of <a href="/wiki/Fish_diseases_and_parasites" title="Fish diseases and parasites">parasites</a> while cleaners benefit from the access to a food source. Some particularly choosy client species have large home ranges that cover several <a href="/wiki/Cleaning_station" title="Cleaning station">cleaning stations</a>, whereas other clients have small ranges and have access to one cleaning station only (resident clients). Field observations, field manipulations, and laboratory experiments revealed that whether or not a client has choice options influences several aspects of both cleaner and client behaviour. Cleaners give choosy clients priority of access. Choosy clients switch partners if cheated by a cleaner by taking a bite of out of the cleaner, whereas resident clients punish cheats. Cleaners and resident clients, but not choosy clients, build up relationships before normal cleaning interactions take place. Cleaners are particularly cooperative if choosy clients are bystanders of an interaction but less so when resident clients are bystanders.<sup id="cite_ref-46" class="reference"><a href="#cite_note-46"><span class="cite-bracket">[</span>45<span class="cite-bracket">]</span></a></sup> </p><p>Researchers tested whether wild white-handed <a href="/wiki/Gibbon" title="Gibbon">gibbon</a> males from <a href="/wiki/Khao_Yai_National_Park" title="Khao Yai National Park">Khao Yai National Park</a>, Thailand, increased their grooming activity when the female partner was fertile.<sup id="cite_ref-47" class="reference"><a href="#cite_note-47"><span class="cite-bracket">[</span>46<span class="cite-bracket">]</span></a></sup> Adult females and males of our study population are codominant (in terms of aggression), they live in pairs or small multi male groups and mate promiscuously. They found that males groomed females more than vice versa and more grooming was exchanged when females were cycling than during pregnancy or lactation. The number of copulations/day was elevated when females were cycling, and females copulated more frequently with males on days when they received more grooming. When males increased their grooming efforts, females also increased their grooming of males, perhaps to equalize give and take. Although grooming might be reciprocated because of intrinsic benefits of receiving grooming, males also interchange grooming as a commodity for sexual opportunities during a female's fertile period.<sup class="noprint Inline-Template" style="margin-left:0.1em; white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Please_clarify" title="Wikipedia:Please clarify"><span title="The text near this tag may need clarification or removal of jargon. (August 2014)">clarification needed</span></a></i>]</sup><sup id="cite_ref-48" class="reference"><a href="#cite_note-48"><span class="cite-bracket">[</span>47<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Examples_in_vertebrates">Examples in vertebrates</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Altruism_(biology)&action=edit&section=8" title="Edit section: Examples in vertebrates"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <div class="mw-heading mw-heading3"><h3 id="Mammals">Mammals</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Altruism_(biology)&action=edit&section=9" title="Edit section: Mammals"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/Wolf" title="Wolf">Wolves</a> and <a href="/wiki/Dog" title="Dog">wild dogs</a> bring meat back to members of the pack not present at the kill;<sup id="cite_ref-49" class="reference"><a href="#cite_note-49"><span class="cite-bracket">[</span>48<span class="cite-bracket">]</span></a></sup> in harsh conditions, the breeding pair of wolves take the greatest share to continue to produce pups.<sup id="cite_ref-50" class="reference"><a href="#cite_note-50"><span class="cite-bracket">[</span>49<span class="cite-bracket">]</span></a></sup></li> <li><a href="/wiki/Mongooses" class="mw-redirect" title="Mongooses">Mongooses</a> support elderly, sick, or injured animals.<sup id="cite_ref-51" class="reference"><a href="#cite_note-51"><span class="cite-bracket">[</span>50<span class="cite-bracket">]</span></a></sup></li> <li><a href="/wiki/Meerkats" class="mw-redirect" title="Meerkats">Meerkats</a> often have one standing guard to warn while the rest feed in case of predator attack.<sup id="cite_ref-52" class="reference"><a href="#cite_note-52"><span class="cite-bracket">[</span>51<span class="cite-bracket">]</span></a></sup></li> <li><a href="/wiki/Raccoon" title="Raccoon">Raccoons</a> inform <a href="/wiki/Conspecificity" class="mw-redirect" title="Conspecificity">conspecifics</a> about feeding grounds by droppings left on <a href="/wiki/Raccoon_latrine" class="mw-redirect" title="Raccoon latrine">commonly shared latrines</a>. A similar information system has been observed to be used by <a href="/wiki/Common_raven" title="Common raven">common ravens</a>.<sup id="cite_ref-53" class="reference"><a href="#cite_note-53"><span class="cite-bracket">[</span>52<span class="cite-bracket">]</span></a></sup></li> <li>Male <a href="/wiki/Baboon" title="Baboon">baboons</a> threaten predators and cover the rear as the troop retreats.<sup id="cite_ref-54" class="reference"><a href="#cite_note-54"><span class="cite-bracket">[</span>53<span class="cite-bracket">]</span></a></sup></li> <li><a href="/wiki/Gibbon" title="Gibbon">Gibbons</a> and <a href="/wiki/Common_chimpanzee" class="mw-redirect" title="Common chimpanzee">chimpanzees</a> with food will, in response to a gesture, share their food with others of the group.<sup id="cite_ref-55" class="reference"><a href="#cite_note-55"><span class="cite-bracket">[</span>54<span class="cite-bracket">]</span></a></sup> Chimpanzees will help humans and <a href="/wiki/Conspecificity" class="mw-redirect" title="Conspecificity">conspecifics</a> without any reward in return.<sup id="cite_ref-56" class="reference"><a href="#cite_note-56"><span class="cite-bracket">[</span>55<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-57" class="reference"><a href="#cite_note-57"><span class="cite-bracket">[</span>56<span class="cite-bracket">]</span></a></sup></li> <li><a href="/wiki/Bonobo" title="Bonobo">Bonobos</a> have been observed aiding injured or disabled bonobos.<sup id="cite_ref-58" class="reference"><a href="#cite_note-58"><span class="cite-bracket">[</span>57<span class="cite-bracket">]</span></a></sup></li> <li><a href="/wiki/Vampire_bats" class="mw-redirect" title="Vampire bats">Vampire bats</a> commonly regurgitate blood to share with unlucky or sick roost mates that have been unable to find a meal, often forming a <a href="/wiki/Buddy_system" title="Buddy system">buddy system</a>.<sup id="cite_ref-59" class="reference"><a href="#cite_note-59"><span class="cite-bracket">[</span>58<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-60" class="reference"><a href="#cite_note-60"><span class="cite-bracket">[</span>59<span class="cite-bracket">]</span></a></sup></li> <li><a href="/wiki/Vervet_monkey" title="Vervet monkey">Vervet monkeys</a> give alarm calls to warn fellow monkeys of the presence of predators, even though in doing so they attract attention to themselves, increasing their personal chance of being attacked.<sup id="cite_ref-61" class="reference"><a href="#cite_note-61"><span class="cite-bracket">[</span>60<span class="cite-bracket">]</span></a></sup></li> <li><a href="/wiki/Lemurs" class="mw-redirect" title="Lemurs">Lemurs</a> of all ages and of both sexes will take care of infants unrelated to them.<sup id="cite_ref-62" class="reference"><a href="#cite_note-62"><span class="cite-bracket">[</span>61<span class="cite-bracket">]</span></a></sup></li> <li><a href="/wiki/Dolphin" title="Dolphin">Dolphins</a> support sick or injured members of their pod, swimming under them for hours at a time and pushing them to the surface so they can breathe.<sup id="cite_ref-63" class="reference"><a href="#cite_note-63"><span class="cite-bracket">[</span>62<span class="cite-bracket">]</span></a></sup></li> <li><a href="/wiki/Walrus" title="Walrus">Walruses</a> have been seen adopting orphans who lost their parents to predators.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (August 2022)">citation needed</span></a></i>]</sup></li> <li><a href="/wiki/African_buffalo" title="African buffalo">African buffalo</a> will rescue a member of the herd captured by predators. (See <a href="/wiki/Battle_at_Kruger" title="Battle at Kruger">Battle at Kruger</a>.)<sup id="cite_ref-64" class="reference"><a href="#cite_note-64"><span class="cite-bracket">[</span>63<span class="cite-bracket">]</span></a></sup></li> <li><a href="/wiki/Humpback_whale" title="Humpback whale">Humpback whales</a> have been observed protecting other species from killer whales.<sup id="cite_ref-65" class="reference"><a href="#cite_note-65"><span class="cite-bracket">[</span>64<span class="cite-bracket">]</span></a></sup></li> <li>Male <a href="/wiki/Przewalski%27s_horse" title="Przewalski's horse">Przewalski's horses</a> have been observed engaging in intervention behaviour when their group members were threatened. They did not distinguish between kin and non-kin members. It has been theorized that they may do this to promote group cohesion and reduce social disruption within the group.<sup id="cite_ref-66" class="reference"><a href="#cite_note-66"><span class="cite-bracket">[</span>65<span class="cite-bracket">]</span></a></sup></li></ul> <div class="mw-heading mw-heading3"><h3 id="Birds">Birds</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Altruism_(biology)&action=edit&section=10" title="Edit section: Birds"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li>In numerous bird species, a breeding pair receives support in raising its young from other "helper" birds, including help with the feeding of its fledglings.<sup id="cite_ref-67" class="reference"><a href="#cite_note-67"><span class="cite-bracket">[</span>66<span class="cite-bracket">]</span></a></sup> Some will even go as far as protecting an unrelated bird's young from predators.<sup id="cite_ref-68" class="reference"><a href="#cite_note-68"><span class="cite-bracket">[</span>67<span class="cite-bracket">]</span></a></sup></li></ul> <div class="mw-heading mw-heading3"><h3 id="Fish">Fish</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Altruism_(biology)&action=edit&section=11" title="Edit section: Fish"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><i><a href="/wiki/Harpagifer_bispinis" title="Harpagifer bispinis">Harpagifer bispinis</a></i>, a species of fish, live in social groups in the harsh environment of the <a href="/wiki/Antarctic_Peninsula" title="Antarctic Peninsula">Antarctic Peninsula</a>. If the parent guarding the nest of eggs is removed, a usually male replacement unrelated to the parents guards the nest from predators and prevents fungal growth that would kill off the brood. There is no clear benefit to the male so the act may be considered altruistic.<sup id="cite_ref-pmid17814861_69-0" class="reference"><a href="#cite_note-pmid17814861-69"><span class="cite-bracket">[</span>68<span class="cite-bracket">]</span></a></sup></li></ul> <div class="mw-heading mw-heading2"><h2 id="Examples_in_invertebrates">Examples in invertebrates</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Altruism_(biology)&action=edit&section=12" title="Edit section: Examples in invertebrates"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li>Some termites, such as <i><a href="/wiki/Globitermes_sulphureus" title="Globitermes sulphureus">Globitermes sulphureus</a></i> and ants, such as <i><a href="/wiki/Camponotus_saundersi" class="mw-redirect" title="Camponotus saundersi">Camponotus saundersi</a></i> release a sticky secretion by fatally rupturing a specialized gland. This <a href="/wiki/Autothysis" title="Autothysis">autothysis</a> altruistically defends the <a href="/wiki/Ant_colony" title="Ant colony">colony</a> at the expense of the individual insect.<sup id="cite_ref-70" class="reference"><a href="#cite_note-70"><span class="cite-bracket">[</span>69<span class="cite-bracket">]</span></a></sup> This can be attributed to the fact that ants share their <a href="/wiki/Gene" title="Gene">genes</a> with the entire colony, and so this behaviour is evolutionarily beneficial (not necessarily for the individual ant but for the continuation of its genetic make-up).</li> <li><i><a href="/wiki/Synalpheus_regalis" title="Synalpheus regalis">Synalpheus regalis</a></i> is a species of eusocial marine snapping shrimp that lives in <a href="/wiki/Sponge" title="Sponge">sponges</a> in coral reefs. They live in colonies of about 300 individuals with one reproductive female.<sup id="cite_ref-Duffy_1996_71-0" class="reference"><a href="#cite_note-Duffy_1996-71"><span class="cite-bracket">[</span>70<span class="cite-bracket">]</span></a></sup> Other colony members defend the colony against intruders, forage, and care for the young.<sup id="cite_ref-Duffy_1996_71-1" class="reference"><a href="#cite_note-Duffy_1996-71"><span class="cite-bracket">[</span>70<span class="cite-bracket">]</span></a></sup> Eusociality in this system entails an adaptive division of labor which results in enhanced reproductive output of the breeders and inclusive fitness benefits for the nonbreeding helpers.<sup id="cite_ref-Duffy_2002_72-0" class="reference"><a href="#cite_note-Duffy_2002-72"><span class="cite-bracket">[</span>71<span class="cite-bracket">]</span></a></sup> <i>S. regalis</i> are exceptionally tolerant of <a href="/wiki/Conspecifics" class="mw-redirect" title="Conspecifics">conspecifics</a> within their colonies due to close genetic relatedness among nestmates. <a href="/wiki/Allozyme" class="mw-redirect" title="Allozyme">Allozyme</a> data reveals that <a href="/wiki/Relatedness" class="mw-redirect" title="Relatedness">relatedness</a> within colonies is high, which is an indication that colonies in this species represent close kin groups.<sup id="cite_ref-73" class="reference"><a href="#cite_note-73"><span class="cite-bracket">[</span>72<span class="cite-bracket">]</span></a></sup> The existence of such groups is an important prerequisite of explanations of social evolution based on <a href="/wiki/Kin_selection" title="Kin selection">kin selection</a>.<sup id="cite_ref-Duffy_2002_72-1" class="reference"><a href="#cite_note-Duffy_2002-72"><span class="cite-bracket">[</span>71<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Hamilton_1964_16-1" class="reference"><a href="#cite_note-Hamilton_1964-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Hamilton_1964b_74-0" class="reference"><a href="#cite_note-Hamilton_1964b-74"><span class="cite-bracket">[</span>73<span class="cite-bracket">]</span></a></sup></li></ul> <div class="mw-heading mw-heading2"><h2 id="Examples_in_protists">Examples in protists</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Altruism_(biology)&action=edit&section=13" title="Edit section: Examples in protists"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>An example of altruism is found in the cellular <a href="/wiki/Slime_mould" class="mw-redirect" title="Slime mould">slime moulds</a>, such as <i><a href="/wiki/Dictyostelid" title="Dictyostelid">Dictyostelium</a> mucoroides</i>. These protists live as individual <a href="/wiki/Amoeba" title="Amoeba">amoebae</a> until starved, at which point they aggregate and form a multicellular fruiting body in which some cells sacrifice themselves to promote the survival of other cells in the fruiting body.<sup id="cite_ref-Reference.com_75-0" class="reference"><a href="#cite_note-Reference.com-75"><span class="cite-bracket">[</span>74<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Examples_in_plants">Examples in plants</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Altruism_(biology)&action=edit&section=14" title="Edit section: Examples in plants"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>When it comes to altruism in <a href="/wiki/Kin_recognition" title="Kin recognition">kin</a>/non-kin recognition, few studies have focused on this trait in crops.<sup id="cite_ref-76" class="reference"><a href="#cite_note-76"><span class="cite-bracket">[</span>75<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-:0_77-0" class="reference"><a href="#cite_note-:0-77"><span class="cite-bracket">[</span>76<span class="cite-bracket">]</span></a></sup> Despite most crops growing in monocultures, there is evidence that they are able to recognize kin and other cultivars.<sup id="cite_ref-:0_77-1" class="reference"><a href="#cite_note-:0-77"><span class="cite-bracket">[</span>76<span class="cite-bracket">]</span></a></sup> For example, cultivated soybean plants were able to recognize a distant ancestor and unrelated neighbors.<sup id="cite_ref-:0_77-2" class="reference"><a href="#cite_note-:0-77"><span class="cite-bracket">[</span>76<span class="cite-bracket">]</span></a></sup> In that experiment, plants were grown in combinations of relation to each other (same cultivar or different cultivar) in pots and their biomass of stems, leaves, and roots were measured to see how the plants responded growing next to kin or non-kin. Crops, unlike wild plants, are highly cultivated. The evolution of traits such as altruism can thus be bred into them through the selection of the trait.<sup id="cite_ref-:1_78-0" class="reference"><a href="#cite_note-:1-78"><span class="cite-bracket">[</span>77<span class="cite-bracket">]</span></a></sup> In agriculture, the importance of yield is stressed, therefore breeding crop cultivars to favor altruism can decrease competitiveness and increase yield.<sup id="cite_ref-:1_78-1" class="reference"><a href="#cite_note-:1-78"><span class="cite-bracket">[</span>77<span class="cite-bracket">]</span></a></sup> It has been shown that using mass <a href="/wiki/Selection_methods_in_plant_breeding_based_on_mode_of_reproduction" title="Selection methods in plant breeding based on mode of reproduction">selection</a> early in the breeding process selects against altruism in an individual, but using mixed individual and <a href="/wiki/Group_selection" title="Group selection">group selection</a> favors altruism.<sup id="cite_ref-:1_78-2" class="reference"><a href="#cite_note-:1-78"><span class="cite-bracket">[</span>77<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Altruism_(biology)&action=edit&section=15" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/Inclusive_fitness" title="Inclusive fitness">Inclusive fitness</a></li> <li><a href="/wiki/Altruism" title="Altruism">Altruism</a></li> <li><a href="/wiki/Reciprocal_altruism" title="Reciprocal altruism">Reciprocal altruism</a></li> <li><a href="/wiki/Koinophilia#The_evolution_of_cooperation" title="Koinophilia">Koinophilia</a></li> <li><a href="/wiki/Cheating_(biology)" title="Cheating (biology)">Cheating (biology)</a></li> <li><a href="/wiki/Co-operation_(evolution)" class="mw-redirect" title="Co-operation (evolution)">Co-operation (evolution)</a></li> <li><a href="/wiki/Evolution_of_morality" title="Evolution of morality">Evolution of morality</a></li> <li><a href="/wiki/Evolutionarily_stable_strategy" title="Evolutionarily stable strategy">Evolutionarily stable strategy</a></li> <li><a href="/wiki/Evolutionary_ethics" title="Evolutionary ethics">Evolutionary ethics</a></li> <li><a href="/wiki/Gene-centered_view_of_evolution" title="Gene-centered view of evolution">Gene-centered view of evolution</a></li> <li><a href="/wiki/Sociobiology" title="Sociobiology">Sociobiology</a></li> <li><a href="/wiki/Rescue_behaviour" title="Rescue behaviour">Rescue behaviour</a></li></ul> <div class="mw-heading mw-heading2"><h2 id="Foot_note">Foot note</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Altruism_(biology)&action=edit&section=16" title="Edit section: Foot note"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist"> <div class="mw-references-wrap"><ol class="references"> <li id="cite_note-19"><span class="mw-cite-backlink"><b><a href="#cite_ref-19">^</a></b></span> <span class="reference-text">An individual's gene complement (or genome) can be represented by the letters of the alphabet. Each letter is represented twice: A<sub>1</sub> and A<sub>2</sub>. The subscript indicates from which parent that copy of A has come. Mostly the two copies are identical, but occasionally they differ slightly. When this individual reproduces sexually, one or other copy of A (chosen randomly) is passed on to offspring-1, who gets its other copy of A from the sexual partner. The same happens with genes B, C, D …. Z. If we denote the two sexual partners by means of subscripts "m" and "f", then the genome of the offspring they produce might consist of A<sub>m2</sub>/A<sub>f1</sub>, B<sub>m2</sub>/B<sub>f2</sub>, C<sub>m1</sub>/C<sub>f1</sub>, D<sub>m1</sub>/D<sub>f1</sub> …… Z<sub>m1</sub>/Z<sub>f2</sub>. Each parent has contributed exactly half of the offspring's genome. So individual "m" shares only half of its genome with its offspring. Suppose individuals "m" and "f" produce a second offspring (offspring-2), whose genome is determined in exactly the same manner. For this example, suppose their genome consists of 52 genes. There is a coin-flip 50% probability that offspring-2 will inherit the same copy of A from "m" as offspring-1 did (i.e. A<sub>m2</sub>). This also applies to gene B and so on through the alphabet. If a coin-flip "heads" means that gene X is the same in offspring-1 as it is in offspring-2, then in 26 flips of the coin, approximately half are going to be "heads", and the rest "tails", i.e. half the genes inherited from parent "m" will be the same in the two offspring. The same will happen to the genes inherited from parent "f". Thus of the 52 genes inherited from the two parents, on average, 13 +  13 =  26 (or half) will be identical in the two sibs. Thus sibs are genetically as similar to one another as a parent is to an offspring.<sup id="cite_ref-17" class="reference"><a href="#cite_note-17"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Smith_1989_18-0" class="reference"><a href="#cite_note-Smith_1989-18"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup></span> </li> </ol></div></div> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Altruism_(biology)&action=edit&section=17" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239543626" /><div class="reflist reflist-columns references-column-width" style="column-width: 33em;"> <ol class="references"> <li id="cite_note-Bell_2008-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-Bell_2008_1-0">^</a></b></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><cite id="CITEREFBell2008" class="citation book cs1">Bell G (2008). <span class="id-lock-limited" title="Free access subject to limited trial, subscription normally required"><a rel="nofollow" class="external text" href="https://archive.org/details/selectionmechani00bell_664"><i>Selection: The Mechanism of Evolution</i></a></span>. Oxford: Oxford University Press. pp. <a rel="nofollow" class="external text" href="https://archive.org/details/selectionmechani00bell_664/page/n381">367</a>–368. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-19-856972-5" title="Special:BookSources/978-0-19-856972-5"><bdi>978-0-19-856972-5</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Selection%3A+The+Mechanism+of+Evolution&rft.place=Oxford&rft.pages=367-368&rft.pub=Oxford+University+Press&rft.date=2008&rft.isbn=978-0-19-856972-5&rft.aulast=Bell&rft.aufirst=G&rft_id=https%3A%2F%2Farchive.org%2Fdetails%2Fselectionmechani00bell_664&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-Okasha_2008-2"><span class="mw-cite-backlink">^ <a href="#cite_ref-Okasha_2008_2-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Okasha_2008_2-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFOkasha2008" class="citation web cs1">Okasha S (2008). <a rel="nofollow" class="external text" href="http://plato.stanford.edu/entries/altruism-biological/">"Biological altruism"</a>. The Stanford Encyclopedia of Philosophy<span class="reference-accessdate">. Retrieved <span class="nowrap">July 20,</span> 2013</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Biological+altruism&rft.pub=The+Stanford+Encyclopedia+of+Philosophy&rft.date=2008&rft.aulast=Okasha&rft.aufirst=S&rft_id=http%3A%2F%2Fplato.stanford.edu%2Fentries%2Faltruism-biological%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-3"><span class="mw-cite-backlink"><b><a href="#cite_ref-3">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.etymonline.com/index.php?term=altruism">"altruism (n .)"</a>. <i>Online Etymology Dictionary</i>. Douglas Harper<span class="reference-accessdate">. Retrieved <span class="nowrap">September 19,</span> 2014</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Online+Etymology+Dictionary&rft.atitle=altruism+%28n+.%29&rft_id=http%3A%2F%2Fwww.etymonline.com%2Findex.php%3Fterm%3Daltruism&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-4">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFTeske2009" class="citation book cs1">Teske N (2009). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=7B38I2UEPa0C"><i>Political Activists in America: The Identity Construction Model of Political Participation</i></a>. University Park, Pa.: Pennsylvania State University Press. p. 101. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/9780271035468" title="Special:BookSources/9780271035468"><bdi>9780271035468</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Political+Activists+in+America%3A+The+Identity+Construction+Model+of+Political+Participation&rft.place=University+Park%2C+Pa.&rft.pages=101&rft.pub=Pennsylvania+State+University+Press&rft.date=2009&rft.isbn=9780271035468&rft.aulast=Teske&rft.aufirst=N&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3D7B38I2UEPa0C&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-5"><span class="mw-cite-backlink"><b><a href="#cite_ref-5">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFCiciloni1825" class="citation book cs1">Ciciloni F (1825). <a rel="nofollow" class="external text" href="https://archive.org/details/agrammaritalian00cicigoog"><i>A Grammar of the Italian Language</i></a>. London: John Murray. p. <a rel="nofollow" class="external text" href="https://archive.org/details/agrammaritalian00cicigoog/page/n81">64</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=A+Grammar+of+the+Italian+Language&rft.place=London&rft.pages=64&rft.pub=John+Murray&rft.date=1825&rft.aulast=Ciciloni&rft.aufirst=F&rft_id=https%3A%2F%2Farchive.org%2Fdetails%2Fagrammaritalian00cicigoog&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-Davies_2012-6"><span class="mw-cite-backlink"><b><a href="#cite_ref-Davies_2012_6-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFDaviesKrebsWest2012" class="citation book cs1">Davies NB, Krebs JR, West SA (April 9, 2012). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=G9mXO5asWi8C">"11"</a>. <i>An Introduction to Behavioural Ecology</i>. John Wiley & Sons. pp. <span class="nowrap">307–</span>333. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-1-4443-3949-9" title="Special:BookSources/978-1-4443-3949-9"><bdi>978-1-4443-3949-9</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=11&rft.btitle=An+Introduction+to+Behavioural+Ecology&rft.pages=%3Cspan+class%3D%22nowrap%22%3E307-%3C%2Fspan%3E333&rft.pub=John+Wiley+%26+Sons&rft.date=2012-04-09&rft.isbn=978-1-4443-3949-9&rft.aulast=Davies&rft.aufirst=NB&rft.au=Krebs%2C+JR&rft.au=West%2C+SA&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DG9mXO5asWi8C&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-7"><span class="mw-cite-backlink"><b><a href="#cite_ref-7">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFGalliardFerriéreDieckmann2003" class="citation journal cs1">Galliard, Jean-François Le; Ferriére, Regis; Dieckmann, Ulf (2003). <a rel="nofollow" class="external text" href="https://doi.org/10.1111%2Fj.0014-3820.2003.tb00211.x">"The Adaptive Dynamics of Altruism in Spatially Heterogeneous Populations"</a>. <i>Evolution</i>. <b>57</b> (1): <span class="nowrap">1–</span>17. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://doi.org/10.1111%2Fj.0014-3820.2003.tb00211.x">10.1111/j.0014-3820.2003.tb00211.x</a></span>. <a href="/wiki/ISSN_(identifier)" class="mw-redirect" title="ISSN (identifier)">ISSN</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/issn/1558-5646">1558-5646</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/12643563">12643563</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:13266199">13266199</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Evolution&rft.atitle=The+Adaptive+Dynamics+of+Altruism+in+Spatially+Heterogeneous+Populations&rft.volume=57&rft.issue=1&rft.pages=%3Cspan+class%3D%22nowrap%22%3E1-%3C%2Fspan%3E17&rft.date=2003&rft.issn=1558-5646&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A13266199%23id-name%3DS2CID&rft_id=info%3Apmid%2F12643563&rft_id=info%3Adoi%2F10.1111%2Fj.0014-3820.2003.tb00211.x&rft.aulast=Galliard&rft.aufirst=Jean-Fran%C3%A7ois+Le&rft.au=Ferri%C3%A9re%2C+Regis&rft.au=Dieckmann%2C+Ulf&rft_id=https%3A%2F%2Fdoi.org%2F10.1111%252Fj.0014-3820.2003.tb00211.x&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-8"><span class="mw-cite-backlink"><b><a href="#cite_ref-8">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFAlcock2009" class="citation book cs1">Alcock A (2009). <i>Animal Behavior</i> (9th ed.). Sinauer Associates. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0878932252" title="Special:BookSources/978-0878932252"><bdi>978-0878932252</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Animal+Behavior&rft.edition=9th&rft.pub=Sinauer+Associates&rft.date=2009&rft.isbn=978-0878932252&rft.aulast=Alcock&rft.aufirst=A&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-9"><span class="mw-cite-backlink"><b><a href="#cite_ref-9">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFTrivers1971" class="citation journal cs1"><a href="/wiki/Robert_L._Trivers" class="mw-redirect" title="Robert L. Trivers">Trivers RL</a> (1971). "The Evolution of Reciprocal Altruism". <i><a href="/wiki/The_Quarterly_Review_of_Biology" title="The Quarterly Review of Biology">The Quarterly Review of Biology</a></i>. <b>46</b> (1): <span class="nowrap">35–</span>57. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1086%2F406755">10.1086/406755</a>. <a href="/wiki/JSTOR_(identifier)" class="mw-redirect" title="JSTOR (identifier)">JSTOR</a> <a rel="nofollow" class="external text" href="https://www.jstor.org/stable/2822435">2822435</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:19027999">19027999</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=The+Quarterly+Review+of+Biology&rft.atitle=The+Evolution+of+Reciprocal+Altruism&rft.volume=46&rft.issue=1&rft.pages=%3Cspan+class%3D%22nowrap%22%3E35-%3C%2Fspan%3E57&rft.date=1971&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A19027999%23id-name%3DS2CID&rft_id=https%3A%2F%2Fwww.jstor.org%2Fstable%2F2822435%23id-name%3DJSTOR&rft_id=info%3Adoi%2F10.1086%2F406755&rft.aulast=Trivers&rft.aufirst=RL&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-10"><span class="mw-cite-backlink"><b><a href="#cite_ref-10">^</a></b></span> <span class="reference-text"><a href="/wiki/George_C._Williams_(biologist)" class="mw-redirect" title="George C. Williams (biologist)">Williams, G.C.</a> (1972) <a href="/wiki/Adaptation_and_Natural_Selection:_A_Critique_of_Some_Current_Evolutionary_Thought" class="mw-redirect" title="Adaptation and Natural Selection: A Critique of Some Current Evolutionary Thought">Adaptation and Natural Selection: A Critique of Some Current Evolutionary Thought</a>. Princeton University Press.<link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-691-02357-3" title="Special:BookSources/0-691-02357-3">0-691-02357-3</a></span> </li> <li id="cite_note-11"><span class="mw-cite-backlink"><b><a href="#cite_ref-11">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFSmith1964" class="citation journal cs1"><a href="/wiki/John_Maynard_Smith" title="John Maynard Smith">Smith JM</a> (1964). "Group selection and kin selection". <i><a href="/wiki/Nature_(journal)" title="Nature (journal)">Nature</a></i>. <b>201</b> (4924): <span class="nowrap">1145–</span>1147. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1964Natur.201.1145S">1964Natur.201.1145S</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1038%2F2011145a0">10.1038/2011145a0</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:4177102">4177102</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Nature&rft.atitle=Group+selection+and+kin+selection&rft.volume=201&rft.issue=4924&rft.pages=%3Cspan+class%3D%22nowrap%22%3E1145-%3C%2Fspan%3E1147&rft.date=1964&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A4177102%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1038%2F2011145a0&rft_id=info%3Abibcode%2F1964Natur.201.1145S&rft.aulast=Smith&rft.aufirst=JM&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-River_Out_of_Eden-12"><span class="mw-cite-backlink"><b><a href="#cite_ref-River_Out_of_Eden_12-0">^</a></b></span> <span class="reference-text">See the chapter <i><a href="/wiki/God%27s_utility_function" class="mw-redirect" title="God's utility function">God's utility function</a></i> in <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFDawkins1995" class="citation book cs1"><a href="/wiki/Richard_Dawkins" title="Richard Dawkins">Dawkins R</a> (1995). <a href="/wiki/River_Out_of_Eden" title="River Out of Eden"><i>River Out of Eden</i></a>. New York: Basic Books. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-465-06990-3" title="Special:BookSources/978-0-465-06990-3"><bdi>978-0-465-06990-3</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=River+Out+of+Eden&rft.place=New+York&rft.pub=Basic+Books&rft.date=1995&rft.isbn=978-0-465-06990-3&rft.aulast=Dawkins&rft.aufirst=R&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-13"><span class="mw-cite-backlink"><b><a href="#cite_ref-13">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFDawkins1994" class="citation journal cs1"><a href="/wiki/Richard_Dawkins" title="Richard Dawkins">Dawkins R</a> (1994). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20060915085010/http://www.simonyi.ox.ac.uk/dawkins/WorldOfDawkins-archive/Dawkins/Work/Articles/1994burying_the_vehicle.shtml">"Burying the Vehicle Commentary on Wilson & Sober: Group Selection"</a>. <i>Behavioral and Brain Sciences</i>. <b>17</b> (4): <span class="nowrap">616–</span>617. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1017%2Fs0140525x00036207">10.1017/s0140525x00036207</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:143378724">143378724</a>. Archived from <a rel="nofollow" class="external text" href="http://www.simonyi.ox.ac.uk/dawkins/WorldOfDawkins-archive/Dawkins/Work/Articles/1994burying_the_vehicle.shtml">the original</a> on September 15, 2006.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Behavioral+and+Brain+Sciences&rft.atitle=Burying+the+Vehicle+Commentary+on+Wilson+%26+Sober%3A+Group+Selection&rft.volume=17&rft.issue=4&rft.pages=%3Cspan+class%3D%22nowrap%22%3E616-%3C%2Fspan%3E617&rft.date=1994&rft_id=info%3Adoi%2F10.1017%2Fs0140525x00036207&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A143378724%23id-name%3DS2CID&rft.aulast=Dawkins&rft.aufirst=R&rft_id=http%3A%2F%2Fwww.simonyi.ox.ac.uk%2Fdawkins%2FWorldOfDawkins-archive%2FDawkins%2FWork%2FArticles%2F1994burying_the_vehicle.shtml&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-14"><span class="mw-cite-backlink"><b><a href="#cite_ref-14">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFDennett1994" class="citation journal cs1"><a href="/wiki/Daniel_Dennett" title="Daniel Dennett">Dennett DC</a> (1994). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20071227065311/http://cogprints.org/281/0/wilsonso.htm">"E Pluribus Unum? Commentary on Wilson & Sober: Group Selection"</a>. <i>Behavioral and Brain Sciences</i>. <b>17</b> (4): <span class="nowrap">617–</span>618. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1017%2Fs0140525x00036219">10.1017/s0140525x00036219</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:146359497">146359497</a>. Archived from <a rel="nofollow" class="external text" href="http://cogprints.org/281/0/wilsonso.htm">the original</a> on December 27, 2007.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Behavioral+and+Brain+Sciences&rft.atitle=E+Pluribus+Unum%3F+Commentary+on+Wilson+%26+Sober%3A+Group+Selection&rft.volume=17&rft.issue=4&rft.pages=%3Cspan+class%3D%22nowrap%22%3E617-%3C%2Fspan%3E618&rft.date=1994&rft_id=info%3Adoi%2F10.1017%2Fs0140525x00036219&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A146359497%23id-name%3DS2CID&rft.aulast=Dennett&rft.aufirst=DC&rft_id=http%3A%2F%2Fcogprints.org%2F281%2F0%2Fwilsonso.htm&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-15"><span class="mw-cite-backlink"><b><a href="#cite_ref-15">^</a></b></span> <span class="reference-text">Pinker, S. (2012). <a rel="nofollow" class="external text" href="http://edge.org/conversation/the-false-allure-of-group-selection">The False Allure of Group Selection</a>. Edge, Jun 19, 2012. <a rel="nofollow" class="external free" href="http://edge.org/conversation/the-false-allure-of-group-selection">http://edge.org/conversation/the-false-allure-of-group-selection</a></span> </li> <li id="cite_note-Hamilton_1964-16"><span class="mw-cite-backlink">^ <a href="#cite_ref-Hamilton_1964_16-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Hamilton_1964_16-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFHamilton1964" class="citation journal cs1">Hamilton WD (July 1964). "The genetical evolution of social behaviour. I". <i>Journal of Theoretical Biology</i>. <b>7</b> (1): <span class="nowrap">1–</span>16. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1964JThBi...7....1H">1964JThBi...7....1H</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1016%2F0022-5193%2864%2990038-4">10.1016/0022-5193(64)90038-4</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/5875341">5875341</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Journal+of+Theoretical+Biology&rft.atitle=The+genetical+evolution+of+social+behaviour.+I&rft.volume=7&rft.issue=1&rft.pages=%3Cspan+class%3D%22nowrap%22%3E1-%3C%2Fspan%3E16&rft.date=1964-07&rft_id=info%3Apmid%2F5875341&rft_id=info%3Adoi%2F10.1016%2F0022-5193%2864%2990038-4&rft_id=info%3Abibcode%2F1964JThBi...7....1H&rft.aulast=Hamilton&rft.aufirst=WD&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-17"><span class="mw-cite-backlink"><b><a href="#cite_ref-17">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFGrafen1984" class="citation book cs1">Grafen A (1984). "Natural selection, kin selection and group selection". In Krebs JR, Davies NB (eds.). <i>Behavioural Ecology. An Evolutionary Approach</i>. Oxford: Blackwell Scientific Publications. pp. <span class="nowrap">70–</span>71. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-632-00998-5" title="Special:BookSources/978-0-632-00998-5"><bdi>978-0-632-00998-5</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=Natural+selection%2C+kin+selection+and+group+selection&rft.btitle=Behavioural+Ecology.+An+Evolutionary+Approach.&rft.place=Oxford&rft.pages=%3Cspan+class%3D%22nowrap%22%3E70-%3C%2Fspan%3E71&rft.pub=Blackwell+Scientific+Publications&rft.date=1984&rft.isbn=978-0-632-00998-5&rft.aulast=Grafen&rft.aufirst=A&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-Smith_1989-18"><span class="mw-cite-backlink"><b><a href="#cite_ref-Smith_1989_18-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFSmith1989" class="citation book cs1">Smith JM (1989). "Evolution in structured populations.". <i>Evolutionary Genetics</i>. Oxford: Oxford University Press. pp. <span class="nowrap">173–</span>175. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0198542155" title="Special:BookSources/978-0198542155"><bdi>978-0198542155</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=Evolution+in+structured+populations.&rft.btitle=Evolutionary+Genetics.&rft.place=Oxford&rft.pages=%3Cspan+class%3D%22nowrap%22%3E173-%3C%2Fspan%3E175&rft.pub=Oxford+University+Press&rft.date=1989&rft.isbn=978-0198542155&rft.aulast=Smith&rft.aufirst=JM&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-20"><span class="mw-cite-backlink"><b><a href="#cite_ref-20">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFTrivers1971" class="citation journal cs1">Trivers RL (1971). "The evolution of reciprocal altruism". <i>Quarterly Review of Biology</i>. <b>46</b>: <span class="nowrap">35–</span>57. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1086%2F406755">10.1086/406755</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:19027999">19027999</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Quarterly+Review+of+Biology&rft.atitle=The+evolution+of+reciprocal+altruism&rft.volume=46&rft.pages=%3Cspan+class%3D%22nowrap%22%3E35-%3C%2Fspan%3E57&rft.date=1971&rft_id=info%3Adoi%2F10.1086%2F406755&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A19027999%23id-name%3DS2CID&rft.aulast=Trivers&rft.aufirst=RL&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-21"><span class="mw-cite-backlink"><b><a href="#cite_ref-21">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFEmlen1984" class="citation book cs1">Emlen ST (1984). "Cooperative breeding in birds and mammals.". In Krebs JR, Davies NB (eds.). <i>Behavioural Ecology. An Evolutionary Approach</i>. Oxford: Blackwell Scientific Publications. pp. <span class="nowrap">328–</span>329. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-632-00998-5" title="Special:BookSources/978-0-632-00998-5"><bdi>978-0-632-00998-5</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=Cooperative+breeding+in+birds+and+mammals.&rft.btitle=Behavioural+Ecology.+An+Evolutionary+Approach.&rft.place=Oxford&rft.pages=%3Cspan+class%3D%22nowrap%22%3E328-%3C%2Fspan%3E329&rft.pub=Blackwell+Scientific+Publications&rft.date=1984&rft.isbn=978-0-632-00998-5&rft.aulast=Emlen&rft.aufirst=ST&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-22"><span class="mw-cite-backlink"><b><a href="#cite_ref-22">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFEberhard1975" class="citation journal cs1">Eberhard MJ (1975). "The evolution of social behaviour by kin selection". <i>Quarterly Review of Biology</i>. <b>50</b>: <span class="nowrap">1–</span>33. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1086%2F408298">10.1086/408298</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:14459515">14459515</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Quarterly+Review+of+Biology&rft.atitle=The+evolution+of+social+behaviour+by+kin+selection&rft.volume=50&rft.pages=%3Cspan+class%3D%22nowrap%22%3E1-%3C%2Fspan%3E33&rft.date=1975&rft_id=info%3Adoi%2F10.1086%2F408298&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A14459515%23id-name%3DS2CID&rft.aulast=Eberhard&rft.aufirst=MJ&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-23"><span class="mw-cite-backlink"><b><a href="#cite_ref-23">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFDawkins1989" class="citation book cs1">Dawkins R (1989). <a rel="nofollow" class="external text" href="https://archive.org/details/selfishgene00dawkrich/page/183">"You scratch my back, I'll ride on yours."</a>. <i>The Selfish Gene</i>. Oxford: Oxford University Press. pp. <a rel="nofollow" class="external text" href="https://archive.org/details/selfishgene00dawkrich/page/183">183–185</a>. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0192860927" title="Special:BookSources/978-0192860927"><bdi>978-0192860927</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=You+scratch+my+back%2C+I%27ll+ride+on+yours.&rft.btitle=The+Selfish+Gene&rft.place=Oxford&rft.pages=183-185&rft.pub=Oxford+University+Press&rft.date=1989&rft.isbn=978-0192860927&rft.aulast=Dawkins&rft.aufirst=R&rft_id=https%3A%2F%2Farchive.org%2Fdetails%2Fselfishgene00dawkrich%2Fpage%2F183&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-Axelrod_1989-24"><span class="mw-cite-backlink">^ <a href="#cite_ref-Axelrod_1989_24-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Axelrod_1989_24-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-Axelrod_1989_24-2"><sup><i><b>c</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFAxelrodHamilton1981" class="citation journal cs1">Axelrod R, Hamilton WD (March 1981). "The evolution of cooperation". <i>Science</i>. <b>211</b> (4489): <span class="nowrap">1390–</span>6. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1981Sci...211.1390A">1981Sci...211.1390A</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1126%2Fscience.7466396">10.1126/science.7466396</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/7466396">7466396</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Science&rft.atitle=The+evolution+of+cooperation&rft.volume=211&rft.issue=4489&rft.pages=%3Cspan+class%3D%22nowrap%22%3E1390-%3C%2Fspan%3E6&rft.date=1981-03&rft_id=info%3Apmid%2F7466396&rft_id=info%3Adoi%2F10.1126%2Fscience.7466396&rft_id=info%3Abibcode%2F1981Sci...211.1390A&rft.aulast=Axelrod&rft.aufirst=R&rft.au=Hamilton%2C+WD&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-Sigmund_1993-25"><span class="mw-cite-backlink">^ <a href="#cite_ref-Sigmund_1993_25-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Sigmund_1993_25-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-Sigmund_1993_25-2"><sup><i><b>c</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFSigmund1993" class="citation book cs1">Sigmund K (1993). <i>Games of Life</i>. Oxford: Oxford University Press. pp. <span class="nowrap">180–</span>206. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/9780198546658" title="Special:BookSources/9780198546658"><bdi>9780198546658</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Games+of+Life.&rft.place=Oxford&rft.pages=%3Cspan+class%3D%22nowrap%22%3E180-%3C%2Fspan%3E206&rft.pub=Oxford+University+Press&rft.date=1993&rft.isbn=9780198546658&rft.aulast=Sigmund&rft.aufirst=K&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-26"><span class="mw-cite-backlink"><b><a href="#cite_ref-26">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFSmith1989" class="citation book cs1">Smith JM (1989). "Evolution in structured populations". <i>Evolutionary Genetics</i>. Oxford: Oxford University Press. pp. <span class="nowrap">168–</span>169, <span class="nowrap">181–</span>183. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0198542155" title="Special:BookSources/978-0198542155"><bdi>978-0198542155</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=Evolution+in+structured+populations&rft.btitle=Evolutionary+Genetics&rft.place=Oxford&rft.pages=%3Cspan+class%3D%22nowrap%22%3E168-%3C%2Fspan%3E169%2C+%3Cspan+class%3D%22nowrap%22%3E181-%3C%2Fspan%3E183&rft.pub=Oxford+University+Press&rft.date=1989&rft.isbn=978-0198542155&rft.aulast=Smith&rft.aufirst=JM&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-27"><span class="mw-cite-backlink"><b><a href="#cite_ref-27">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFGodfray1992" class="citation journal cs1">Godfray HC (1992). "The evolution of forgiveness". <i>Nature</i>. <b>355</b> (6357): <span class="nowrap">206–</span>207. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1992Natur.355..206G">1992Natur.355..206G</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1038%2F355206a0">10.1038/355206a0</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:4335611">4335611</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Nature&rft.atitle=The+evolution+of+forgiveness&rft.volume=355&rft.issue=6357&rft.pages=%3Cspan+class%3D%22nowrap%22%3E206-%3C%2Fspan%3E207&rft.date=1992&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A4335611%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1038%2F355206a0&rft_id=info%3Abibcode%2F1992Natur.355..206G&rft.aulast=Godfray&rft.aufirst=HC&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-28"><span class="mw-cite-backlink"><b><a href="#cite_ref-28">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFNowakSigmund1993" class="citation journal cs1">Nowak M, Sigmund K (June 1993). <a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC46660">"Chaos and the evolution of cooperation"</a>. <i>Proceedings of the National Academy of Sciences of the United States of America</i>. <b>90</b> (11): <span class="nowrap">5091–</span>4. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1993PNAS...90.5091N">1993PNAS...90.5091N</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://doi.org/10.1073%2Fpnas.90.11.5091">10.1073/pnas.90.11.5091</a></span>. <a href="/wiki/PMC_(identifier)" class="mw-redirect" title="PMC (identifier)">PMC</a> <span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC46660">46660</a></span>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/8506355">8506355</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Proceedings+of+the+National+Academy+of+Sciences+of+the+United+States+of+America&rft.atitle=Chaos+and+the+evolution+of+cooperation&rft.volume=90&rft.issue=11&rft.pages=%3Cspan+class%3D%22nowrap%22%3E5091-%3C%2Fspan%3E4&rft.date=1993-06&rft_id=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpmc%2Farticles%2FPMC46660%23id-name%3DPMC&rft_id=info%3Apmid%2F8506355&rft_id=info%3Adoi%2F10.1073%2Fpnas.90.11.5091&rft_id=info%3Abibcode%2F1993PNAS...90.5091N&rft.aulast=Nowak&rft.aufirst=M&rft.au=Sigmund%2C+K&rft_id=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpmc%2Farticles%2FPMC46660&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-Koeslag_1997-29"><span class="mw-cite-backlink">^ <a href="#cite_ref-Koeslag_1997_29-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Koeslag_1997_29-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFKoeslag1997" class="citation journal cs1">Koeslag JH (November 1997). "Sex, the Prisoner's Dilemma Game, and the evolutionary inevitability of cooperation". <i>Journal of Theoretical Biology</i>. <b>189</b> (1): <span class="nowrap">53–</span>61. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1997JThBi.189...53K">1997JThBi.189...53K</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1006%2Fjtbi.1997.0496">10.1006/jtbi.1997.0496</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/9398503">9398503</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Journal+of+Theoretical+Biology&rft.atitle=Sex%2C+the+Prisoner%27s+Dilemma+Game%2C+and+the+evolutionary+inevitability+of+cooperation&rft.volume=189&rft.issue=1&rft.pages=%3Cspan+class%3D%22nowrap%22%3E53-%3C%2Fspan%3E61&rft.date=1997-11&rft_id=info%3Apmid%2F9398503&rft_id=info%3Adoi%2F10.1006%2Fjtbi.1997.0496&rft_id=info%3Abibcode%2F1997JThBi.189...53K&rft.aulast=Koeslag&rft.aufirst=JH&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-30"><span class="mw-cite-backlink"><b><a href="#cite_ref-30">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFZahavi1975" class="citation journal cs1">Zahavi A (September 1975). "Mate selection-a selection for a handicap". <i>Journal of Theoretical Biology</i>. <b>53</b> (1): <span class="nowrap">205–</span>14. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1975JThBi..53..205Z">1975JThBi..53..205Z</a>. <a href="/wiki/CiteSeerX_(identifier)" class="mw-redirect" title="CiteSeerX (identifier)">CiteSeerX</a> <span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.586.3819">10.1.1.586.3819</a></span>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1016%2F0022-5193%2875%2990111-3">10.1016/0022-5193(75)90111-3</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/1195756">1195756</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Journal+of+Theoretical+Biology&rft.atitle=Mate+selection-a+selection+for+a+handicap&rft.volume=53&rft.issue=1&rft.pages=%3Cspan+class%3D%22nowrap%22%3E205-%3C%2Fspan%3E14&rft.date=1975-09&rft_id=https%3A%2F%2Fciteseerx.ist.psu.edu%2Fviewdoc%2Fsummary%3Fdoi%3D10.1.1.586.3819%23id-name%3DCiteSeerX&rft_id=info%3Apmid%2F1195756&rft_id=info%3Adoi%2F10.1016%2F0022-5193%2875%2990111-3&rft_id=info%3Abibcode%2F1975JThBi..53..205Z&rft.aulast=Zahavi&rft.aufirst=A&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-Zahavi_1997-31"><span class="mw-cite-backlink">^ <a href="#cite_ref-Zahavi_1997_31-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Zahavi_1997_31-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFZahavi1977" class="citation journal cs1">Zahavi A (August 1977). "The cost of honesty (further remarks on the handicap principle)". <i>Journal of Theoretical Biology</i>. <b>67</b> (3): <span class="nowrap">603–</span>5. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1977JThBi..67..603Z">1977JThBi..67..603Z</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1016%2F0022-5193%2877%2990061-3">10.1016/0022-5193(77)90061-3</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/904334">904334</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Journal+of+Theoretical+Biology&rft.atitle=The+cost+of+honesty+%28further+remarks+on+the+handicap+principle%29&rft.volume=67&rft.issue=3&rft.pages=%3Cspan+class%3D%22nowrap%22%3E603-%3C%2Fspan%3E5&rft.date=1977-08&rft_id=info%3Apmid%2F904334&rft_id=info%3Adoi%2F10.1016%2F0022-5193%2877%2990061-3&rft_id=info%3Abibcode%2F1977JThBi..67..603Z&rft.aulast=Zahavi&rft.aufirst=A&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-32"><span class="mw-cite-backlink"><b><a href="#cite_ref-32">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFZahavi1997" class="citation book cs1">Zahavi A (1997). <a rel="nofollow" class="external text" href="https://archive.org/details/handicapprincipl0000zeha"><i>The handicap principle: a missing piece of Darwin's puzzle</i></a>. Oxford: Oxford University Press. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-19-510035-8" title="Special:BookSources/978-0-19-510035-8"><bdi>978-0-19-510035-8</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+handicap+principle%3A+a+missing+piece+of+Darwin%27s+puzzle&rft.place=Oxford&rft.pub=Oxford+University+Press&rft.date=1997&rft.isbn=978-0-19-510035-8&rft.aulast=Zahavi&rft.aufirst=A&rft_id=https%3A%2F%2Farchive.org%2Fdetails%2Fhandicapprincipl0000zeha&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-33"><span class="mw-cite-backlink"><b><a href="#cite_ref-33">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFGrafen1990" class="citation journal cs1">Grafen A (June 1990). "Biological signals as handicaps". <i>Journal of Theoretical Biology</i>. <b>144</b> (4): <span class="nowrap">517–</span>46. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1990JThBi.144..517G">1990JThBi.144..517G</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1016%2FS0022-5193%2805%2980088-8">10.1016/S0022-5193(05)80088-8</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/2402153">2402153</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Journal+of+Theoretical+Biology&rft.atitle=Biological+signals+as+handicaps&rft.volume=144&rft.issue=4&rft.pages=%3Cspan+class%3D%22nowrap%22%3E517-%3C%2Fspan%3E46&rft.date=1990-06&rft_id=info%3Apmid%2F2402153&rft_id=info%3Adoi%2F10.1016%2FS0022-5193%2805%2980088-8&rft_id=info%3Abibcode%2F1990JThBi.144..517G&rft.aulast=Grafen&rft.aufirst=A&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-34"><span class="mw-cite-backlink"><b><a href="#cite_ref-34">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFJohnstoneGrafen1993" class="citation journal cs1">Johnstone RA, Grafen A (1993). "Dishonesty and the handicap principle". <i>Anim. Behav</i>. <b>46</b> (4): <span class="nowrap">759–</span>764. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1006%2Fanbe.1993.1253">10.1006/anbe.1993.1253</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:53191998">53191998</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Anim.+Behav.&rft.atitle=Dishonesty+and+the+handicap+principle&rft.volume=46&rft.issue=4&rft.pages=%3Cspan+class%3D%22nowrap%22%3E759-%3C%2Fspan%3E764&rft.date=1993&rft_id=info%3Adoi%2F10.1006%2Fanbe.1993.1253&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A53191998%23id-name%3DS2CID&rft.aulast=Johnstone&rft.aufirst=RA&rft.au=Grafen%2C+A&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-35"><span class="mw-cite-backlink"><b><a href="#cite_ref-35">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFHockeyDeanRyan2005" class="citation book cs1">Hockey PA, Dean WR, Ryan PG (2005). <i>Roberts Birds of Southern Africa</i>. Cape Town: Trustees of the John Voelcker Bird Book Fund. pp. 176, 193.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Roberts+Birds+of+Southern+Africa&rft.place=Cape+Town&rft.pages=176%2C+193&rft.pub=Trustees+of+the+John+Voelcker+Bird+Book+Fund&rft.date=2005&rft.aulast=Hockey&rft.aufirst=PA&rft.au=Dean%2C+WR&rft.au=Ryan%2C+PG&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-Fisher_1930-36"><span class="mw-cite-backlink">^ <a href="#cite_ref-Fisher_1930_36-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Fisher_1930_36-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFFisher1930" class="citation book cs1">Fisher R (1930). <i>The Genetical Theory of Natural Selection</i>. Oxford: Clarendon Press.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Genetical+Theory+of+Natural+Selection&rft.place=Oxford&rft.pub=Clarendon+Press&rft.date=1930&rft.aulast=Fisher&rft.aufirst=R&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span>.</span> </li> <li id="cite_note-37"><span class="mw-cite-backlink"><b><a href="#cite_ref-37">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFSymons1979" class="citation book cs1">Symons D (1979). <i>The Evolution of Human Sexuality</i>. Oxford: Oxford University Press.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+Evolution+of+Human+Sexuality&rft.place=Oxford&rft.pub=Oxford+University+Press&rft.date=1979&rft.aulast=Symons&rft.aufirst=D&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-Langlois_1990-38"><span class="mw-cite-backlink"><b><a href="#cite_ref-Langlois_1990_38-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFLangloisRoggman1990" class="citation journal cs1">Langlois JH, Roggman L (1990). "Attractive faces are only average". <i>Psychol. Sci</i>. <b>1</b> (2): <span class="nowrap">115–</span>121. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1111%2Fj.1467-9280.1990.tb00079.x">10.1111/j.1467-9280.1990.tb00079.x</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:18557871">18557871</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Psychol.+Sci.&rft.atitle=Attractive+faces+are+only+average&rft.volume=1&rft.issue=2&rft.pages=%3Cspan+class%3D%22nowrap%22%3E115-%3C%2Fspan%3E121&rft.date=1990&rft_id=info%3Adoi%2F10.1111%2Fj.1467-9280.1990.tb00079.x&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A18557871%23id-name%3DS2CID&rft.aulast=Langlois&rft.aufirst=JH&rft.au=Roggman%2C+L&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-Koeslag_1990-39"><span class="mw-cite-backlink">^ <a href="#cite_ref-Koeslag_1990_39-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Koeslag_1990_39-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFKoeslag1990" class="citation journal cs1">Koeslag JH (May 1990). "Koinophilia groups sexual creatures into species, promotes stasis, and stabilizes social behaviour". <i>Journal of Theoretical Biology</i>. <b>144</b> (1): <span class="nowrap">15–</span>35. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1990JThBi.144...15K">1990JThBi.144...15K</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1016%2Fs0022-5193%2805%2980297-8">10.1016/s0022-5193(05)80297-8</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/2200930">2200930</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Journal+of+Theoretical+Biology&rft.atitle=Koinophilia+groups+sexual+creatures+into+species%2C+promotes+stasis%2C+and+stabilizes+social+behaviour&rft.volume=144&rft.issue=1&rft.pages=%3Cspan+class%3D%22nowrap%22%3E15-%3C%2Fspan%3E35&rft.date=1990-05&rft_id=info%3Apmid%2F2200930&rft_id=info%3Adoi%2F10.1016%2Fs0022-5193%2805%2980297-8&rft_id=info%3Abibcode%2F1990JThBi.144...15K&rft.aulast=Koeslag&rft.aufirst=JH&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-Poelstra_2014-40"><span class="mw-cite-backlink"><b><a href="#cite_ref-Poelstra_2014_40-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFPoelstraVijayBossuLantz2014" class="citation journal cs1">Poelstra JW, Vijay N, Bossu CM, Lantz H, Ryll B, Müller I, et al. (June 2014). <a rel="nofollow" class="external text" href="http://nbn-resolving.de/urn:nbn:de:bsz:352-0-260687">"The genomic landscape underlying phenotypic integrity in the face of gene flow in crows"</a>. <i>Science</i>. <b>344</b> (6190): <span class="nowrap">1410–</span>4. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2014Sci...344.1410P">2014Sci...344.1410P</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1126%2Fscience.1253226">10.1126/science.1253226</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/24948738">24948738</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:14431499">14431499</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Science&rft.atitle=The+genomic+landscape+underlying+phenotypic+integrity+in+the+face+of+gene+flow+in+crows&rft.volume=344&rft.issue=6190&rft.pages=%3Cspan+class%3D%22nowrap%22%3E1410-%3C%2Fspan%3E4&rft.date=2014-06&rft_id=info%3Adoi%2F10.1126%2Fscience.1253226&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A14431499%23id-name%3DS2CID&rft_id=info%3Apmid%2F24948738&rft_id=info%3Abibcode%2F2014Sci...344.1410P&rft.aulast=Poelstra&rft.aufirst=JW&rft.au=Vijay%2C+N&rft.au=Bossu%2C+CM&rft.au=Lantz%2C+H&rft.au=Ryll%2C+B&rft.au=M%C3%BCller%2C+I&rft.au=Baglione%2C+V&rft.au=Unneberg%2C+P&rft.au=Wikelski%2C+M&rft.au=Grabherr%2C+MG&rft.au=Wolf%2C+JB&rft_id=http%3A%2F%2Fnbn-resolving.de%2Furn%3Anbn%3Ade%3Absz%3A352-0-260687&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-Koeslag_2003-41"><span class="mw-cite-backlink"><b><a href="#cite_ref-Koeslag_2003_41-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFKoeslagTerblanche2003" class="citation journal cs1">Koeslag JH, Terblanche E (October 2003). "Evolution of cooperation: cooperation defeats defection in the cornfield model". <i>Journal of Theoretical Biology</i>. <b>224</b> (3): <span class="nowrap">399–</span>410. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2003JThBi.224..399K">2003JThBi.224..399K</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1016%2Fs0022-5193%2803%2900188-7">10.1016/s0022-5193(03)00188-7</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/12941597">12941597</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Journal+of+Theoretical+Biology&rft.atitle=Evolution+of+cooperation%3A+cooperation+defeats+defection+in+the+cornfield+model&rft.volume=224&rft.issue=3&rft.pages=%3Cspan+class%3D%22nowrap%22%3E399-%3C%2Fspan%3E410&rft.date=2003-10&rft_id=info%3Apmid%2F12941597&rft_id=info%3Adoi%2F10.1016%2Fs0022-5193%2803%2900188-7&rft_id=info%3Abibcode%2F2003JThBi.224..399K&rft.aulast=Koeslag&rft.aufirst=JH&rft.au=Terblanche%2C+E&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-42"><span class="mw-cite-backlink"><b><a href="#cite_ref-42">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFIbrahim2022" class="citation journal cs1">Ibrahim, Ahmed (2022). <a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9449918">"The conditional defector strategies can violate the most crucial supporting mechanisms of cooperation"</a>. <i>Scientific Reports</i>. <b>12</b> (1): 15157. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2022NatSR..1215157I">2022NatSR..1215157I</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1038%2Fs41598-022-18797-2">10.1038/s41598-022-18797-2</a>. <a href="/wiki/PMC_(identifier)" class="mw-redirect" title="PMC (identifier)">PMC</a> <span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9449918">9449918</a></span>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/36071078">36071078</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Scientific+Reports&rft.atitle=The+conditional+defector+strategies+can+violate+the+most+crucial+supporting+mechanisms+of+cooperation&rft.volume=12&rft.issue=1&rft.pages=15157&rft.date=2022&rft_id=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpmc%2Farticles%2FPMC9449918%23id-name%3DPMC&rft_id=info%3Apmid%2F36071078&rft_id=info%3Adoi%2F10.1038%2Fs41598-022-18797-2&rft_id=info%3Abibcode%2F2022NatSR..1215157I&rft.aulast=Ibrahim&rft.aufirst=Ahmed&rft_id=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpmc%2Farticles%2FPMC9449918&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-43"><span class="mw-cite-backlink"><b><a href="#cite_ref-43">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://dictionary.reference.com/browse/altruism">"Altruism | Define Altruism at Dictionary.com"</a>. Dictionary.reference.com<span class="reference-accessdate">. Retrieved <span class="nowrap">June 4,</span> 2018</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Altruism+%26%23124%3B+Define+Altruism+at+Dictionary.com&rft.pub=Dictionary.reference.com&rft_id=http%3A%2F%2Fdictionary.reference.com%2Fbrowse%2Faltruism&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-pmid15915815-44"><span class="mw-cite-backlink"><b><a href="#cite_ref-pmid15915815_44-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFde_Waal2005" class="citation journal cs1">de Waal FB (April 2005). "How animals do business?". <i>Scientific American</i>. <b>292</b> (4): <span class="nowrap">54–</span>61. <a href="/wiki/JSTOR_(identifier)" class="mw-redirect" title="JSTOR (identifier)">JSTOR</a> <a rel="nofollow" class="external text" href="https://www.jstor.org/stable/26060958">26060958</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/15915815">15915815</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Scientific+American&rft.atitle=How+animals+do+business%3F&rft.volume=292&rft.issue=4&rft.pages=%3Cspan+class%3D%22nowrap%22%3E54-%3C%2Fspan%3E61&rft.date=2005-04&rft_id=https%3A%2F%2Fwww.jstor.org%2Fstable%2F26060958%23id-name%3DJSTOR&rft_id=info%3Apmid%2F15915815&rft.aulast=de+Waal&rft.aufirst=FB&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-45"><span class="mw-cite-backlink"><b><a href="#cite_ref-45">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFNoeVoelkl2013" class="citation book cs1">Noe R, Voelkl B (2013). "Cooperation and biological markets: The power of partner choice.". In Sterelny K, Joyce R, Calcott B, Fraser B (eds.). <i>Cooperation and its evolution</i>. Cambridge, MA US: The MIT Press. pp. <span class="nowrap">131–</span>151.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=Cooperation+and+biological+markets%3A+The+power+of+partner+choice.&rft.btitle=Cooperation+and+its+evolution&rft.place=Cambridge%2C+MA+US&rft.pages=%3Cspan+class%3D%22nowrap%22%3E131-%3C%2Fspan%3E151&rft.pub=The+MIT+Press&rft.date=2013&rft.aulast=Noe&rft.aufirst=R&rft.au=Voelkl%2C+B&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-46"><span class="mw-cite-backlink"><b><a href="#cite_ref-46">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFBsharyNoë2003" class="citation book cs1">Bshary R, Noë R (2003). "Biological markets: the ubiquitous influence of partner choice on the dynamics of cleaner fish-client reef fish interactions.". In Hammerstein P (ed.). <i>Genetic and cultural evolution of cooperation</i>. Vol. 9. Cambridge, MA US: MIT Press. pp. <span class="nowrap">167–</span>184.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=Biological+markets%3A+the+ubiquitous+influence+of+partner+choice+on+the+dynamics+of+cleaner+fish-client+reef+fish+interactions.&rft.btitle=Genetic+and+cultural+evolution+of+cooperation&rft.place=Cambridge%2C+MA+US&rft.pages=%3Cspan+class%3D%22nowrap%22%3E167-%3C%2Fspan%3E184&rft.pub=MIT+Press&rft.date=2003&rft.aulast=Bshary&rft.aufirst=R&rft.au=No%C3%AB%2C+R&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-47"><span class="mw-cite-backlink"><b><a href="#cite_ref-47">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFBareliiReichardMundry2011" class="citation journal cs1">Barelii C, Reichard U, Mundry R (2011). "Is grooming used as a commodity in wild white-handed gibbons, Hylobates lar?". <i>Animal Behaviour</i>. <b>82</b> (4): <span class="nowrap">801–</span>809. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1016%2Fj.anbehav.2011.07.012">10.1016/j.anbehav.2011.07.012</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:53190848">53190848</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Animal+Behaviour&rft.atitle=Is+grooming+used+as+a+commodity+in+wild+white-handed+gibbons%2C+Hylobates+lar%3F&rft.volume=82&rft.issue=4&rft.pages=%3Cspan+class%3D%22nowrap%22%3E801-%3C%2Fspan%3E809&rft.date=2011&rft_id=info%3Adoi%2F10.1016%2Fj.anbehav.2011.07.012&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A53190848%23id-name%3DS2CID&rft.aulast=Barelii&rft.aufirst=C&rft.au=Reichard%2C+U&rft.au=Mundry%2C+R&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-48"><span class="mw-cite-backlink"><b><a href="#cite_ref-48">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation journal cs1"><a rel="nofollow" class="external text" href="https://dx.doi.org/10.1016/0003-3472(67)90034-6">"Animal behaviour monographs"</a>. <i>Animal Behaviour</i>. <b>15</b> (4): <span class="nowrap">401–</span>402. October 1967. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1016%2F0003-3472%2867%2990034-6">10.1016/0003-3472(67)90034-6</a>. <a href="/wiki/ISSN_(identifier)" class="mw-redirect" title="ISSN (identifier)">ISSN</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/issn/0003-3472">0003-3472</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Animal+Behaviour&rft.atitle=Animal+behaviour+monographs&rft.volume=15&rft.issue=4&rft.pages=%3Cspan+class%3D%22nowrap%22%3E401-%3C%2Fspan%3E402&rft.date=1967-10&rft_id=info%3Adoi%2F10.1016%2F0003-3472%2867%2990034-6&rft.issn=0003-3472&rft_id=http%3A%2F%2Fdx.doi.org%2F10.1016%2F0003-3472%2867%2990034-6&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-49"><span class="mw-cite-backlink"><b><a href="#cite_ref-49">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFSinger2011" class="citation book cs1">Singer P (2011). <i>The expanding circle: ethics, evolution, and moral progress</i>. Princeton, NJ: Princeton University Press. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-1-4008-3843-1" title="Special:BookSources/978-1-4008-3843-1"><bdi>978-1-4008-3843-1</bdi></a>. <a href="/wiki/OCLC_(identifier)" class="mw-redirect" title="OCLC (identifier)">OCLC</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/oclc/733058004">733058004</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=The+expanding+circle%3A+ethics%2C+evolution%2C+and+moral+progress&rft.place=Princeton%2C+NJ&rft.pub=Princeton+University+Press&rft.date=2011&rft_id=info%3Aoclcnum%2F733058004&rft.isbn=978-1-4008-3843-1&rft.aulast=Singer&rft.aufirst=P&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-50"><span class="mw-cite-backlink"><b><a href="#cite_ref-50">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFMech2003" class="citation book cs1">Mech LD (2003). <i>Wolves: Behavior,Ecology and conservation</i>. university of Chicago press. p. 58. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-226-51696-7" title="Special:BookSources/978-0-226-51696-7"><bdi>978-0-226-51696-7</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Wolves%3A+Behavior%2CEcology+and+conservation&rft.pages=58&rft.pub=university+of+Chicago+press&rft.date=2003&rft.isbn=978-0-226-51696-7&rft.aulast=Mech&rft.aufirst=LD&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-51"><span class="mw-cite-backlink"><b><a href="#cite_ref-51">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFBaker1984" class="citation journal cs1">Baker CM (January 1, 1984). "Social care behaviour of captive slender mongooses (<i>Herpestes sanguineus</i>)". <i>Mammalia</i>. <b>48</b> (1): <span class="nowrap">43–</span>52. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1515%2Fmamm.1984.48.1.43">10.1515/mamm.1984.48.1.43</a>. <a href="/wiki/ISSN_(identifier)" class="mw-redirect" title="ISSN (identifier)">ISSN</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/issn/1864-1547">1864-1547</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:84868529">84868529</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Mammalia&rft.atitle=Social+care+behaviour+of+captive+slender+mongooses+%28Herpestes+sanguineus%29&rft.volume=48&rft.issue=1&rft.pages=%3Cspan+class%3D%22nowrap%22%3E43-%3C%2Fspan%3E52&rft.date=1984-01-01&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A84868529%23id-name%3DS2CID&rft.issn=1864-1547&rft_id=info%3Adoi%2F10.1515%2Fmamm.1984.48.1.43&rft.aulast=Baker&rft.aufirst=CM&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-52"><span class="mw-cite-backlink"><b><a href="#cite_ref-52">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFAllchin2009" class="citation journal cs1">Allchin D (September 2009). <a rel="nofollow" class="external text" href="https://doi.org/10.1007%2Fs12052-009-0167-7">"The evolution of morality"</a>. <i>Evolution: Education and Outreach</i>. <b>2</b> (4): <span class="nowrap">590–</span>601. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://doi.org/10.1007%2Fs12052-009-0167-7">10.1007/s12052-009-0167-7</a></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Evolution%3A+Education+and+Outreach&rft.atitle=The+evolution+of+morality&rft.volume=2&rft.issue=4&rft.pages=%3Cspan+class%3D%22nowrap%22%3E590-%3C%2Fspan%3E601&rft.date=2009-09&rft_id=info%3Adoi%2F10.1007%2Fs12052-009-0167-7&rft.aulast=Allchin&rft.aufirst=D&rft_id=https%3A%2F%2Fdoi.org%2F10.1007%252Fs12052-009-0167-7&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-53"><span class="mw-cite-backlink"><b><a href="#cite_ref-53">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFHohmannBartussekBöer2001" class="citation book cs1 cs1-prop-foreign-lang-source">Hohmann U, Bartussek I, Böer B (2001). <i>Der Waschbär</i> (in German). Reutlingen, Germany: Oertel+Spörer. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-3-88627-301-0" title="Special:BookSources/978-3-88627-301-0"><bdi>978-3-88627-301-0</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Der+Waschb%C3%A4r&rft.place=Reutlingen%2C+Germany&rft.pub=Oertel%2BSp%C3%B6rer&rft.date=2001&rft.isbn=978-3-88627-301-0&rft.aulast=Hohmann&rft.aufirst=U&rft.au=Bartussek%2C+I&rft.au=B%C3%B6er%2C+B&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-54"><span class="mw-cite-backlink"><b><a href="#cite_ref-54">^</a></b></span> <span class="reference-text">Robert Ardrey, <i>African Ganesis</i> (N.Y.: Dell publishers, 1961), pp. 80-81, 136.</span> </li> <li id="cite_note-55"><span class="mw-cite-backlink"><b><a href="#cite_ref-55">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFYamamotoHumleTanaka2009" class="citation journal cs1">Yamamoto S, Humle T, Tanaka M (October 2009). <a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2757899">"Chimpanzees help each other upon request"</a>. <i>PLOS ONE</i>. <b>4</b> (10): e7416. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2009PLoSO...4.7416Y">2009PLoSO...4.7416Y</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://doi.org/10.1371%2Fjournal.pone.0007416">10.1371/journal.pone.0007416</a></span>. <a href="/wiki/PMC_(identifier)" class="mw-redirect" title="PMC (identifier)">PMC</a> <span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2757899">2757899</a></span>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/19826478">19826478</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=PLOS+ONE&rft.atitle=Chimpanzees+help+each+other+upon+request&rft.volume=4&rft.issue=10&rft.pages=e7416&rft.date=2009-10&rft_id=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpmc%2Farticles%2FPMC2757899%23id-name%3DPMC&rft_id=info%3Apmid%2F19826478&rft_id=info%3Adoi%2F10.1371%2Fjournal.pone.0007416&rft_id=info%3Abibcode%2F2009PLoSO...4.7416Y&rft.aulast=Yamamoto&rft.aufirst=S&rft.au=Humle%2C+T&rft.au=Tanaka%2C+M&rft_id=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpmc%2Farticles%2FPMC2757899&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-56"><span class="mw-cite-backlink"><b><a href="#cite_ref-56">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.sciencedaily.com/releases/2007/06/070625085134.htm">"Human-like Altruism Shown In Chimpanzees"</a>. <i>ScienceDaily</i>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=ScienceDaily&rft.atitle=Human-like+Altruism+Shown+In+Chimpanzees&rft_id=https%3A%2F%2Fwww.sciencedaily.com%2Freleases%2F2007%2F06%2F070625085134.htm&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-57"><span class="mw-cite-backlink"><b><a href="#cite_ref-57">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFBrosnan_SFSilk_JBHenrich_JMareno_MC2009" class="citation journal cs1">Brosnan SF; <a href="/wiki/Joan_Silk" title="Joan Silk">Silk JB</a>; Henrich J; Mareno MC; Lambeth SP; Schapiro SJ (July 2009). <a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2698971">"Chimpanzees (Pan troglodytes) do not develop contingent reciprocity in an experimental task"</a>. <i>Animal Cognition</i>. <b>12</b> (4): <span class="nowrap">587–</span>97. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1007%2Fs10071-009-0218-z">10.1007/s10071-009-0218-z</a>. <a href="/wiki/PMC_(identifier)" class="mw-redirect" title="PMC (identifier)">PMC</a> <span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2698971">2698971</a></span>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/19259709">19259709</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Animal+Cognition&rft.atitle=Chimpanzees+%28Pan+troglodytes%29+do+not+develop+contingent+reciprocity+in+an+experimental+task&rft.volume=12&rft.issue=4&rft.pages=%3Cspan+class%3D%22nowrap%22%3E587-%3C%2Fspan%3E97&rft.date=2009-07&rft_id=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpmc%2Farticles%2FPMC2698971%23id-name%3DPMC&rft_id=info%3Apmid%2F19259709&rft_id=info%3Adoi%2F10.1007%2Fs10071-009-0218-z&rft.au=Brosnan+SF&rft.au=Silk+JB&rft.au=Henrich+J&rft.au=Mareno+MC&rft.au=Lambeth+SP&rft.au=Schapiro+SJ&rft_id=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpmc%2Farticles%2FPMC2698971&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-58"><span class="mw-cite-backlink"><b><a href="#cite_ref-58">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20051013062832/http://www.sciencefriday.com/pages/2005/Oct/hour2_100705.html">"October 7, 2005, Hour Two"</a>. Archived from <a rel="nofollow" class="external text" href="http://www.sciencefriday.com/pages/2005/Oct/hour2_100705.html">the original</a> on October 13, 2005<span class="reference-accessdate">. Retrieved <span class="nowrap">October 9,</span> 2005</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=October+7%2C+2005%2C+Hour+Two&rft_id=http%3A%2F%2Fwww.sciencefriday.com%2Fpages%2F2005%2FOct%2Fhour2_100705.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-59"><span class="mw-cite-backlink"><b><a href="#cite_ref-59">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFde_Waal1996" class="citation book cs1"><a href="/wiki/Frans_de_Waal" title="Frans de Waal">de Waal F</a> (1996). <a rel="nofollow" class="external text" href="https://archive.org/details/goodnaturedorigi00waal/page/20"><i>Good Natured</i></a>. <a href="/wiki/Harvard_University_Press" title="Harvard University Press">Harvard University Press</a>. pp. <a rel="nofollow" class="external text" href="https://archive.org/details/goodnaturedorigi00waal/page/20">20–21</a>. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-674-35660-3" title="Special:BookSources/978-0-674-35660-3"><bdi>978-0-674-35660-3</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Good+Natured&rft.pages=20-21&rft.pub=Harvard+University+Press&rft.date=1996&rft.isbn=978-0-674-35660-3&rft.aulast=de+Waal&rft.aufirst=F&rft_id=https%3A%2F%2Farchive.org%2Fdetails%2Fgoodnaturedorigi00waal%2Fpage%2F20&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-60"><span class="mw-cite-backlink"><b><a href="#cite_ref-60">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFPerry2002" class="citation web cs1">Perry J (April 19, 2002). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20090920154140/http://www.bio.davidson.edu/people/vecase/behavior/Spring2002/Perry/altruism.html">"Reciprocal Altruism in Vampire Bats"</a>. Archived from <a rel="nofollow" class="external text" href="http://www.bio.davidson.edu/people/vecase/behavior/Spring2002/Perry/altruism.html">the original</a> on September 20, 2009<span class="reference-accessdate">. Retrieved <span class="nowrap">October 10,</span> 2009</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Reciprocal+Altruism+in+Vampire+Bats&rft.date=2002-04-19&rft.aulast=Perry&rft.aufirst=J&rft_id=http%3A%2F%2Fwww.bio.davidson.edu%2Fpeople%2Fvecase%2Fbehavior%2FSpring2002%2FPerry%2Faltruism.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-61"><span class="mw-cite-backlink"><b><a href="#cite_ref-61">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFCheneySeyfarth1990" class="citation book cs1">Cheney DL, Seyfarth RM (1990). <span class="id-lock-registration" title="Free registration required"><a rel="nofollow" class="external text" href="https://archive.org/details/howmonkeysseewor00chenrich"><i>How monkeys see the world: Inside the mind of another species</i></a></span>. University of Chicago Press. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-226-10246-7" title="Special:BookSources/978-0-226-10246-7"><bdi>978-0-226-10246-7</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=How+monkeys+see+the+world%3A+Inside+the+mind+of+another+species&rft.pub=University+of+Chicago+Press&rft.date=1990&rft.isbn=978-0-226-10246-7&rft.aulast=Cheney&rft.aufirst=DL&rft.au=Seyfarth%2C+RM&rft_id=https%3A%2F%2Farchive.org%2Fdetails%2Fhowmonkeysseewor00chenrich&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-62"><span class="mw-cite-backlink"><b><a href="#cite_ref-62">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFPereiraIzard1989" class="citation journal cs1">Pereira ME, Izard MK (1989). "Lactation and care for unrelated infants in forest-living ringtailed Lemurs". <i>American Journal of Primatology</i>. <b>18</b> (2): <span class="nowrap">101–</span>108. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1002%2Fajp.1350180204">10.1002/ajp.1350180204</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/31964040">31964040</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:85433858">85433858</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=American+Journal+of+Primatology&rft.atitle=Lactation+and+care+for+unrelated+infants+in+forest-living+ringtailed+Lemurs&rft.volume=18&rft.issue=2&rft.pages=%3Cspan+class%3D%22nowrap%22%3E101-%3C%2Fspan%3E108&rft.date=1989&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A85433858%23id-name%3DS2CID&rft_id=info%3Apmid%2F31964040&rft_id=info%3Adoi%2F10.1002%2Fajp.1350180204&rft.aulast=Pereira&rft.aufirst=ME&rft.au=Izard%2C+MK&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-63"><span class="mw-cite-backlink"><b><a href="#cite_ref-63">^</a></b></span> <span class="reference-text">Davidson College, biology department (2001) <a rel="nofollow" class="external text" href="http://www.bio.davidson.edu/people/vecase/behavior/Spring2001/Ewart/Altruism.html">Bottlenose Dolphins – Altruism</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20100106122007/http://www.bio.davidson.edu/people/vecase/behavior/Spring2001/Ewart/Altruism.html">Archived</a> January 6, 2010, at the <a href="/wiki/Wayback_Machine" title="Wayback Machine">Wayback Machine</a>, article retrieved March 11, 2009. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20110927120530/http://www.bio.davidson.edu/people/vecase/behavior/Spring2001/Ewart/Altruism.html">Archived version</a></span> </li> <li id="cite_note-64"><span class="mw-cite-backlink"><b><a href="#cite_ref-64">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFBudzinskiSchlosberg2007" class="citation web cs1">Budzinski D, Schlosberg J (May 3, 2007). <a rel="nofollow" class="external text" href="https://www.youtube.com/watch?v=LU8DDYz68kM">"Battle at Kruger"</a>. <i>Youtube</i>. <a rel="nofollow" class="external text" href="https://ghostarchive.org/varchive/youtube/20211213/LU8DDYz68kM">Archived</a> from the original on December 13, 2021.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Youtube&rft.atitle=Battle+at+Kruger&rft.date=2007-05-03&rft.aulast=Budzinski&rft.aufirst=D&rft.au=Schlosberg%2C+J&rft_id=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DLU8DDYz68kM&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-65"><span class="mw-cite-backlink"><b><a href="#cite_ref-65">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFPitman2017" class="citation journal cs1">Pitman RL (2017). <a rel="nofollow" class="external text" href="https://doi.org/10.1111%2Fmms.12343">"Humpback whales interfering when mammal-eating killer whales attack other species: Mobbing behavior and interspecific altruism?"</a>. <i>Marine Mammal Science</i>. <b>33</b> (1): <span class="nowrap">7–</span>58. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2017MMamS..33....7P">2017MMamS..33....7P</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://doi.org/10.1111%2Fmms.12343">10.1111/mms.12343</a></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Marine+Mammal+Science&rft.atitle=Humpback+whales+interfering+when+mammal-eating+killer+whales+attack+other+species%3A+Mobbing+behavior+and+interspecific+altruism%3F&rft.volume=33&rft.issue=1&rft.pages=%3Cspan+class%3D%22nowrap%22%3E7-%3C%2Fspan%3E58&rft.date=2017&rft_id=info%3Adoi%2F10.1111%2Fmms.12343&rft_id=info%3Abibcode%2F2017MMamS..33....7P&rft.aulast=Pitman&rft.aufirst=RL&rft_id=https%3A%2F%2Fdoi.org%2F10.1111%252Fmms.12343&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-66"><span class="mw-cite-backlink"><b><a href="#cite_ref-66">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFKruegerSchneiderFlaugerHeinze2015" class="citation journal cs1">Krueger K, Schneider G, Flauger B, Heinze J (December 2015). <a rel="nofollow" class="external text" href="https://epub.uni-regensburg.de/36808/1/EpUB_UREG_Krueger_Heinze_%20Schneider_Flauger_Interventions_P_%20Animal_Behaviour.pdf">"Context-dependent third-party intervention in agonistic encounters of male Przewalski horses"</a> <span class="cs1-format">(PDF)</span>. <i>Behavioural Processes</i>. <b>121</b>: <span class="nowrap">54–</span>62. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1016%2Fj.beproc.2015.10.009">10.1016/j.beproc.2015.10.009</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/26478251">26478251</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:3647491">3647491</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Behavioural+Processes&rft.atitle=Context-dependent+third-party+intervention+in+agonistic+encounters+of+male+Przewalski+horses&rft.volume=121&rft.pages=%3Cspan+class%3D%22nowrap%22%3E54-%3C%2Fspan%3E62&rft.date=2015-12&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A3647491%23id-name%3DS2CID&rft_id=info%3Apmid%2F26478251&rft_id=info%3Adoi%2F10.1016%2Fj.beproc.2015.10.009&rft.aulast=Krueger&rft.aufirst=K&rft.au=Schneider%2C+G&rft.au=Flauger%2C+B&rft.au=Heinze%2C+J&rft_id=https%3A%2F%2Fepub.uni-regensburg.de%2F36808%2F1%2FEpUB_UREG_Krueger_Heinze_%2520Schneider_Flauger_Interventions_P_%2520Animal_Behaviour.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-67"><span class="mw-cite-backlink"><b><a href="#cite_ref-67">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFBrown2007" class="citation news cs1">Brown D (August 17, 2007). <a rel="nofollow" class="external text" href="https://www.washingtonpost.com/wp-dyn/content/article/2007/08/16/AR2007081602257.html">"Birds' Cooperative Breeding Sheds Light on Altruism"</a>. <i>The Washington Post</i><span class="reference-accessdate">. Retrieved <span class="nowrap">April 23,</span> 2010</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=The+Washington+Post&rft.atitle=Birds%27+Cooperative+Breeding+Sheds+Light+on+Altruism&rft.date=2007-08-17&rft.aulast=Brown&rft.aufirst=D&rft_id=https%3A%2F%2Fwww.washingtonpost.com%2Fwp-dyn%2Fcontent%2Farticle%2F2007%2F08%2F16%2FAR2007081602257.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-68"><span class="mw-cite-backlink"><b><a href="#cite_ref-68">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFFackelmann1989" class="citation news cs1">Fackelmann KA (1989). <a rel="nofollow" class="external text" href="http://findarticles.com/p/articles/mi_m1200/is_n23_v135/ai_7680117">"Avian altruism: African birds sacrifice self-interest to help their kin – white-fronted bee eaters"</a>. <i>Science News</i>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Science+News&rft.atitle=Avian+altruism%3A+African+birds+sacrifice+self-interest+to+help+their+kin+%E2%80%93+white-fronted+bee+eaters&rft.date=1989&rft.aulast=Fackelmann&rft.aufirst=KA&rft_id=http%3A%2F%2Ffindarticles.com%2Fp%2Farticles%2Fmi_m1200%2Fis_n23_v135%2Fai_7680117&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-pmid17814861-69"><span class="mw-cite-backlink"><b><a href="#cite_ref-pmid17814861_69-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFDaniels1979" class="citation journal cs1">Daniels RA (August 1979). "Nest Guard Replacement in the Antarctic Fish Harpagifer bispinis: Possible Altruistic Behavior". <i>Science</i>. <b>205</b> (4408). New York, N.Y.: <span class="nowrap">831–</span>3. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1979Sci...205..831D">1979Sci...205..831D</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1126%2Fscience.205.4408.831">10.1126/science.205.4408.831</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/17814861">17814861</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:1628887">1628887</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Science&rft.atitle=Nest+Guard+Replacement+in+the+Antarctic+Fish+Harpagifer+bispinis%3A+Possible+Altruistic+Behavior&rft.volume=205&rft.issue=4408&rft.pages=%3Cspan+class%3D%22nowrap%22%3E831-%3C%2Fspan%3E3&rft.date=1979-08&rft_id=info%3Adoi%2F10.1126%2Fscience.205.4408.831&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A1628887%23id-name%3DS2CID&rft_id=info%3Apmid%2F17814861&rft_id=info%3Abibcode%2F1979Sci...205..831D&rft.aulast=Daniels&rft.aufirst=RA&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-70"><span class="mw-cite-backlink"><b><a href="#cite_ref-70">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFBordereauRobertVan_TuyenPeppuy1997" class="citation journal cs1">Bordereau C, Robert A, Van Tuyen V, Peppuy A (1997). "Suicidal defensive behavior by frontal gland dehiscence in <i>Globitermes sulphureus</i> Haviland soldiers (Isoptera)". <i>Insectes Sociaux</i>. <b>44</b> (3): <span class="nowrap">289–</span>297. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1007%2Fs000400050049">10.1007/s000400050049</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:19770804">19770804</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Insectes+Sociaux&rft.atitle=Suicidal+defensive+behavior+by+frontal+gland+dehiscence+in+Globitermes+sulphureus+Haviland+soldiers+%28Isoptera%29&rft.volume=44&rft.issue=3&rft.pages=%3Cspan+class%3D%22nowrap%22%3E289-%3C%2Fspan%3E297&rft.date=1997&rft_id=info%3Adoi%2F10.1007%2Fs000400050049&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A19770804%23id-name%3DS2CID&rft.aulast=Bordereau&rft.aufirst=C&rft.au=Robert%2C+A&rft.au=Van+Tuyen%2C+V&rft.au=Peppuy%2C+A&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-Duffy_1996-71"><span class="mw-cite-backlink">^ <a href="#cite_ref-Duffy_1996_71-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Duffy_1996_71-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFDuffy1996" class="citation journal cs1">Duffy JE (1996). <a rel="nofollow" class="external text" href="http://decapoda.nhm.org/pdfs/25410/25410.pdf">"Eusociality in a coral-reef shrimp"</a> <span class="cs1-format">(PDF)</span>. <i><a href="/wiki/Nature_(journal)" title="Nature (journal)">Nature</a></i>. <b>381</b> (6582): <span class="nowrap">512–</span>514. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1996Natur.381..512D">1996Natur.381..512D</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1038%2F381512a0">10.1038/381512a0</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:33166806">33166806</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Nature&rft.atitle=Eusociality+in+a+coral-reef+shrimp&rft.volume=381&rft.issue=6582&rft.pages=%3Cspan+class%3D%22nowrap%22%3E512-%3C%2Fspan%3E514&rft.date=1996&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A33166806%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1038%2F381512a0&rft_id=info%3Abibcode%2F1996Natur.381..512D&rft.aulast=Duffy&rft.aufirst=JE&rft_id=http%3A%2F%2Fdecapoda.nhm.org%2Fpdfs%2F25410%2F25410.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-Duffy_2002-72"><span class="mw-cite-backlink">^ <a href="#cite_ref-Duffy_2002_72-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Duffy_2002_72-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFDuffyMorrisonMacdonald2002" class="citation journal cs1">Duffy JE, Morrison CL, Macdonald KS (2002). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20150803214955/http://www.vims.edu/research/units/labgroups/marine_biodiversity/publications/_pdf/Duffy_et_al_2002_BES.PDF">"Colony defense and behavioral differentiation in the eusocial shrimp <i>Synalpheus regalis</i>"</a> <span class="cs1-format">(PDF)</span>. <i><a href="/wiki/Behavioral_Ecology_and_Sociobiology" title="Behavioral Ecology and Sociobiology">Behavioral Ecology and Sociobiology</a></i>. <b>51</b> (5): <span class="nowrap">488–</span>495. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2002BEcoS..51..488D">2002BEcoS..51..488D</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1007%2Fs00265-002-0455-5">10.1007/s00265-002-0455-5</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:25384748">25384748</a>. Archived from <a rel="nofollow" class="external text" href="http://www.vims.edu/research/units/labgroups/marine_biodiversity/publications/_pdf/Duffy_et_al_2002_BES.PDF">the original</a> <span class="cs1-format">(PDF)</span> on August 3, 2015.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Behavioral+Ecology+and+Sociobiology&rft.atitle=Colony+defense+and+behavioral+differentiation+in+the+eusocial+shrimp+Synalpheus+regalis&rft.volume=51&rft.issue=5&rft.pages=%3Cspan+class%3D%22nowrap%22%3E488-%3C%2Fspan%3E495&rft.date=2002&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A25384748%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1007%2Fs00265-002-0455-5&rft_id=info%3Abibcode%2F2002BEcoS..51..488D&rft.aulast=Duffy&rft.aufirst=JE&rft.au=Morrison%2C+CL&rft.au=Macdonald%2C+KS&rft_id=http%3A%2F%2Fwww.vims.edu%2Fresearch%2Funits%2Flabgroups%2Fmarine_biodiversity%2Fpublications%2F_pdf%2FDuffy_et_al_2002_BES.PDF&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-73"><span class="mw-cite-backlink"><b><a href="#cite_ref-73">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFParkerSnowSchugBooton1998" class="citation journal cs1">Parker PG, Snow AA, Schug MD, Booton GC, Fuerst PA (1998). "What molecules can tell us about populations: Choosing and using a molecular marker". <i>Ecology</i>. <b>79</b> (2): <span class="nowrap">361–</span>382. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1998Ecol...79..361P">1998Ecol...79..361P</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.2307%2F176939">10.2307/176939</a>. <a href="/wiki/JSTOR_(identifier)" class="mw-redirect" title="JSTOR (identifier)">JSTOR</a> <a rel="nofollow" class="external text" href="https://www.jstor.org/stable/176939">176939</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Ecology&rft.atitle=What+molecules+can+tell+us+about+populations%3A+Choosing+and+using+a+molecular+marker&rft.volume=79&rft.issue=2&rft.pages=%3Cspan+class%3D%22nowrap%22%3E361-%3C%2Fspan%3E382&rft.date=1998&rft_id=https%3A%2F%2Fwww.jstor.org%2Fstable%2F176939%23id-name%3DJSTOR&rft_id=info%3Adoi%2F10.2307%2F176939&rft_id=info%3Abibcode%2F1998Ecol...79..361P&rft.aulast=Parker&rft.aufirst=PG&rft.au=Snow%2C+AA&rft.au=Schug%2C+MD&rft.au=Booton%2C+GC&rft.au=Fuerst%2C+PA&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-Hamilton_1964b-74"><span class="mw-cite-backlink"><b><a href="#cite_ref-Hamilton_1964b_74-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFHamilton1964" class="citation journal cs1">Hamilton WD (July 1964). "The genetical evolution of social behaviour. II". <i>Journal of Theoretical Biology</i>. <b>7</b> (1): <span class="nowrap">17–</span>52. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1964JThBi...7...17H">1964JThBi...7...17H</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1016%2F0022-5193%2864%2990039-6">10.1016/0022-5193(64)90039-6</a>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/5875340">5875340</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Journal+of+Theoretical+Biology&rft.atitle=The+genetical+evolution+of+social+behaviour.+II&rft.volume=7&rft.issue=1&rft.pages=%3Cspan+class%3D%22nowrap%22%3E17-%3C%2Fspan%3E52&rft.date=1964-07&rft_id=info%3Apmid%2F5875340&rft_id=info%3Adoi%2F10.1016%2F0022-5193%2864%2990039-6&rft_id=info%3Abibcode%2F1964JThBi...7...17H&rft.aulast=Hamilton&rft.aufirst=WD&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-Reference.com-75"><span class="mw-cite-backlink"><b><a href="#cite_ref-Reference.com_75-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20121108211148/http://www.reference.com/browse/altruism">"Altruism"</a>. Reference.com. Archived from <a rel="nofollow" class="external text" href="http://www.reference.com/browse/altruism">the original</a> on November 8, 2012<span class="reference-accessdate">. Retrieved <span class="nowrap">July 20,</span> 2013</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Altruism&rft.pub=Reference.com&rft_id=http%3A%2F%2Fwww.reference.com%2Fbrowse%2Faltruism&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-76"><span class="mw-cite-backlink"><b><a href="#cite_ref-76">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFFangClarkZhengIyer-Pascuzzi2013" class="citation journal cs1">Fang, Suqin; Clark, Randy T.; Zheng, Ying; Iyer-Pascuzzi, Anjali S.; Weitz, Joshua S.; Kochian, Leon V.; Edelsbrunner, Herbert; Liao, Hong; Benfey, Philip N. (February 12, 2013). <a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3574932">"Genotypic recognition and spatial responses by rice roots"</a>. <i>Proceedings of the National Academy of Sciences</i>. <b>110</b> (7): <span class="nowrap">2670–</span>2675. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2013PNAS..110.2670F">2013PNAS..110.2670F</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://doi.org/10.1073%2Fpnas.1222821110">10.1073/pnas.1222821110</a></span>. <a href="/wiki/ISSN_(identifier)" class="mw-redirect" title="ISSN (identifier)">ISSN</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/issn/0027-8424">0027-8424</a>. <a href="/wiki/PMC_(identifier)" class="mw-redirect" title="PMC (identifier)">PMC</a> <span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3574932">3574932</a></span>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/23362379">23362379</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Proceedings+of+the+National+Academy+of+Sciences&rft.atitle=Genotypic+recognition+and+spatial+responses+by+rice+roots&rft.volume=110&rft.issue=7&rft.pages=%3Cspan+class%3D%22nowrap%22%3E2670-%3C%2Fspan%3E2675&rft.date=2013-02-12&rft_id=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpmc%2Farticles%2FPMC3574932%23id-name%3DPMC&rft_id=info%3Abibcode%2F2013PNAS..110.2670F&rft_id=info%3Apmid%2F23362379&rft_id=info%3Adoi%2F10.1073%2Fpnas.1222821110&rft.issn=0027-8424&rft.aulast=Fang&rft.aufirst=Suqin&rft.au=Clark%2C+Randy+T.&rft.au=Zheng%2C+Ying&rft.au=Iyer-Pascuzzi%2C+Anjali+S.&rft.au=Weitz%2C+Joshua+S.&rft.au=Kochian%2C+Leon+V.&rft.au=Edelsbrunner%2C+Herbert&rft.au=Liao%2C+Hong&rft.au=Benfey%2C+Philip+N.&rft_id=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpmc%2Farticles%2FPMC3574932&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-:0-77"><span class="mw-cite-backlink">^ <a href="#cite_ref-:0_77-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-:0_77-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-:0_77-2"><sup><i><b>c</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFMurphyVan_AckerRajcanSwanton2017" class="citation journal cs1">Murphy, Guillermo P.; Van Acker, Rene; Rajcan, Istvan; Swanton, Clarence J. (2017). <a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5319353">"Identity recognition in response to different levels of genetic relatedness in commercial soya bean"</a>. <i>Royal Society Open Science</i>. <b>4</b> (1): 160879. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2017RSOS....460879M">2017RSOS....460879M</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1098%2Frsos.160879">10.1098/rsos.160879</a>. <a href="/wiki/PMC_(identifier)" class="mw-redirect" title="PMC (identifier)">PMC</a> <span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5319353">5319353</a></span>. <a href="/wiki/PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/28280587">28280587</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Royal+Society+Open+Science&rft.atitle=Identity+recognition+in+response+to+different+levels+of+genetic+relatedness+in+commercial+soya+bean&rft.volume=4&rft.issue=1&rft.pages=160879&rft.date=2017&rft_id=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpmc%2Farticles%2FPMC5319353%23id-name%3DPMC&rft_id=info%3Apmid%2F28280587&rft_id=info%3Adoi%2F10.1098%2Frsos.160879&rft_id=info%3Abibcode%2F2017RSOS....460879M&rft.aulast=Murphy&rft.aufirst=Guillermo+P.&rft.au=Van+Acker%2C+Rene&rft.au=Rajcan%2C+Istvan&rft.au=Swanton%2C+Clarence+J.&rft_id=https%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fpmc%2Farticles%2FPMC5319353&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> <li id="cite_note-:1-78"><span class="mw-cite-backlink">^ <a href="#cite_ref-:1_78-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-:1_78-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-:1_78-2"><sup><i><b>c</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFMurphySwantonVan_AckerDudley2017" class="citation journal cs1">Murphy, Guillermo P.; Swanton, Clarence J.; Van Acker, Rene C.; Dudley, Susan A. (July 2017). Gibson, David (ed.). <a rel="nofollow" class="external text" href="https://doi.org/10.1111%2F1365-2745.12787">"Kin recognition, multilevel selection and altruism in crop sustainability"</a>. <i>Journal of Ecology</i>. <b>105</b> (4): <span class="nowrap">930–</span>934. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2017JEcol.105..930M">2017JEcol.105..930M</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://doi.org/10.1111%2F1365-2745.12787">10.1111/1365-2745.12787</a></span>. <a href="/wiki/ISSN_(identifier)" class="mw-redirect" title="ISSN (identifier)">ISSN</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/issn/0022-0477">0022-0477</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:90467342">90467342</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Journal+of+Ecology&rft.atitle=Kin+recognition%2C+multilevel+selection+and+altruism+in+crop+sustainability&rft.volume=105&rft.issue=4&rft.pages=%3Cspan+class%3D%22nowrap%22%3E930-%3C%2Fspan%3E934&rft.date=2017-07&rft_id=info%3Adoi%2F10.1111%2F1365-2745.12787&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A90467342%23id-name%3DS2CID&rft.issn=0022-0477&rft_id=info%3Abibcode%2F2017JEcol.105..930M&rft.aulast=Murphy&rft.aufirst=Guillermo+P.&rft.au=Swanton%2C+Clarence+J.&rft.au=Van+Acker%2C+Rene+C.&rft.au=Dudley%2C+Susan+A.&rft_id=https%3A%2F%2Fdoi.org%2F10.1111%252F1365-2745.12787&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></span> </li> </ol></div> <div class="mw-heading mw-heading2"><h2 id="Further_reading">Further reading</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Altruism_(biology)&action=edit&section=18" title="Edit section: Further reading"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239549316">.mw-parser-output .refbegin{margin-bottom:0.5em}.mw-parser-output .refbegin-hanging-indents>ul{margin-left:0}.mw-parser-output .refbegin-hanging-indents>ul>li{margin-left:0;padding-left:3.2em;text-indent:-3.2em}.mw-parser-output .refbegin-hanging-indents ul,.mw-parser-output .refbegin-hanging-indents ul li{list-style:none}@media(max-width:720px){.mw-parser-output .refbegin-hanging-indents>ul>li{padding-left:1.6em;text-indent:-1.6em}}.mw-parser-output .refbegin-columns{margin-top:0.3em}.mw-parser-output .refbegin-columns ul{margin-top:0}.mw-parser-output .refbegin-columns li{page-break-inside:avoid;break-inside:avoid-column}@media screen{.mw-parser-output .refbegin{font-size:90%}}</style><div class="refbegin" style=""> <ul><li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFStoel2012" class="citation journal cs1">Stoel A (2012). <a rel="nofollow" class="external text" href="http://www.terasemjournals.com/PCJournal/PC0701/Papers/Stoel.pdf">"The meme of altruism and degrees of personhood"</a> <span class="cs1-format">(PDF)</span>. <i>Journal of Personal Cyberconsciousness</i>. <b>7</b> (1): <span class="nowrap">27–</span>36.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Journal+of+Personal+Cyberconsciousness&rft.atitle=The+meme+of+altruism+and+degrees+of+personhood&rft.volume=7&rft.issue=1&rft.pages=%3Cspan+class%3D%22nowrap%22%3E27-%3C%2Fspan%3E36&rft.date=2012&rft.aulast=Stoel&rft.aufirst=A&rft_id=http%3A%2F%2Fwww.terasemjournals.com%2FPCJournal%2FPC0701%2FPapers%2FStoel.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3AAltruism+%28biology%29" class="Z3988"></span></li></ul> </div> <div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Altruism_(biology)&action=edit&section=19" title="Edit section: External links"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a rel="nofollow" class="external text" href="http://plato.stanford.edu/entries/altruism-biological/">Biological Altruism </a></li> <li><a rel="nofollow" class="external text" href="http://www.iussi.org/">International Union for the Study of Social Insects</a></li> <li><a rel="nofollow" class="external text" href="https://web.archive.org/web/20060827121734/http://www.ruf.rice.edu/~evolve/pdf/20002001/CurBio2002_12_R832.pdf">Quick Guide: Kin Selection (Current Biology)</a></li> <li><a rel="nofollow" class="external text" href="https://web.archive.org/web/20070928003506/http://westgroup.icapb.ed.ac.uk/pdf/West_etal_06_altruism.pdf">Quick Guide: Altruism (Current Biology)</a></li> <li><a rel="nofollow" class="external text" href="https://web.archive.org/web/20061027145548/http://www.dogsinthenews.com/stories/060929a.php">"Mutt-ernal Instincts"</a> An article about dogs caring for other species' young (cats, tigers, etc.).</li></ul> <div class="navbox-styles"><style data-mw-deduplicate="TemplateStyles:r1129693374">.mw-parser-output .hlist dl,.mw-parser-output .hlist ol,.mw-parser-output .hlist ul{margin:0;padding:0}.mw-parser-output .hlist dd,.mw-parser-output .hlist dt,.mw-parser-output .hlist li{margin:0;display:inline}.mw-parser-output .hlist.inline,.mw-parser-output .hlist.inline dl,.mw-parser-output .hlist.inline ol,.mw-parser-output .hlist.inline ul,.mw-parser-output .hlist dl dl,.mw-parser-output .hlist dl ol,.mw-parser-output .hlist dl ul,.mw-parser-output .hlist ol dl,.mw-parser-output .hlist ol ol,.mw-parser-output .hlist ol ul,.mw-parser-output .hlist ul dl,.mw-parser-output .hlist ul ol,.mw-parser-output .hlist ul ul{display:inline}.mw-parser-output .hlist .mw-empty-li{display:none}.mw-parser-output .hlist dt::after{content:": "}.mw-parser-output .hlist dd::after,.mw-parser-output .hlist li::after{content:" · ";font-weight:bold}.mw-parser-output .hlist dd:last-child::after,.mw-parser-output .hlist dt:last-child::after,.mw-parser-output .hlist li:last-child::after{content:none}.mw-parser-output .hlist dd dd:first-child::before,.mw-parser-output .hlist dd dt:first-child::before,.mw-parser-output .hlist dd li:first-child::before,.mw-parser-output .hlist dt dd:first-child::before,.mw-parser-output .hlist dt dt:first-child::before,.mw-parser-output .hlist dt li:first-child::before,.mw-parser-output .hlist li dd:first-child::before,.mw-parser-output .hlist li dt:first-child::before,.mw-parser-output .hlist li li:first-child::before{content:" (";font-weight:normal}.mw-parser-output .hlist dd dd:last-child::after,.mw-parser-output .hlist dd dt:last-child::after,.mw-parser-output .hlist dd li:last-child::after,.mw-parser-output .hlist dt dd:last-child::after,.mw-parser-output .hlist dt dt:last-child::after,.mw-parser-output .hlist dt li:last-child::after,.mw-parser-output .hlist li dd:last-child::after,.mw-parser-output .hlist li dt:last-child::after,.mw-parser-output .hlist li li:last-child::after{content:")";font-weight:normal}.mw-parser-output .hlist ol{counter-reset:listitem}.mw-parser-output .hlist ol>li{counter-increment:listitem}.mw-parser-output .hlist ol>li::before{content:" "counter(listitem)"\a0 "}.mw-parser-output .hlist dd ol>li:first-child::before,.mw-parser-output .hlist dt ol>li:first-child::before,.mw-parser-output .hlist li ol>li:first-child::before{content:" ("counter(listitem)"\a0 "}</style><style data-mw-deduplicate="TemplateStyles:r1236075235">.mw-parser-output .navbox{box-sizing:border-box;border:1px solid #a2a9b1;width:100%;clear:both;font-size:88%;text-align:center;padding:1px;margin:1em auto 0}.mw-parser-output .navbox .navbox{margin-top:0}.mw-parser-output .navbox+.navbox,.mw-parser-output .navbox+.navbox-styles+.navbox{margin-top:-1px}.mw-parser-output .navbox-inner,.mw-parser-output .navbox-subgroup{width:100%}.mw-parser-output .navbox-group,.mw-parser-output .navbox-title,.mw-parser-output .navbox-abovebelow{padding:0.25em 1em;line-height:1.5em;text-align:center}.mw-parser-output .navbox-group{white-space:nowrap;text-align:right}.mw-parser-output .navbox,.mw-parser-output .navbox-subgroup{background-color:#fdfdfd}.mw-parser-output .navbox-list{line-height:1.5em;border-color:#fdfdfd}.mw-parser-output .navbox-list-with-group{text-align:left;border-left-width:2px;border-left-style:solid}.mw-parser-output tr+tr>.navbox-abovebelow,.mw-parser-output tr+tr>.navbox-group,.mw-parser-output tr+tr>.navbox-image,.mw-parser-output tr+tr>.navbox-list{border-top:2px solid #fdfdfd}.mw-parser-output .navbox-title{background-color:#ccf}.mw-parser-output .navbox-abovebelow,.mw-parser-output .navbox-group,.mw-parser-output .navbox-subgroup .navbox-title{background-color:#ddf}.mw-parser-output .navbox-subgroup .navbox-group,.mw-parser-output .navbox-subgroup .navbox-abovebelow{background-color:#e6e6ff}.mw-parser-output .navbox-even{background-color:#f7f7f7}.mw-parser-output .navbox-odd{background-color:transparent}.mw-parser-output .navbox .hlist td dl,.mw-parser-output .navbox .hlist td ol,.mw-parser-output .navbox .hlist td ul,.mw-parser-output .navbox td.hlist dl,.mw-parser-output .navbox td.hlist ol,.mw-parser-output .navbox td.hlist ul{padding:0.125em 0}.mw-parser-output .navbox .navbar{display:block;font-size:100%}.mw-parser-output .navbox-title .navbar{float:left;text-align:left;margin-right:0.5em}body.skin--responsive .mw-parser-output .navbox-image img{max-width:none!important}@media print{body.ns-0 .mw-parser-output .navbox{display:none!important}}</style></div><div role="navigation" class="navbox" aria-labelledby="Evolutionary_biology753" style="padding:3px"><table class="nowraplinks hlist mw-collapsible autocollapse navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="col" class="navbox-title" colspan="2"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374" /><style data-mw-deduplicate="TemplateStyles:r1239400231">.mw-parser-output .navbar{display:inline;font-size:88%;font-weight:normal}.mw-parser-output .navbar-collapse{float:left;text-align:left}.mw-parser-output .navbar-boxtext{word-spacing:0}.mw-parser-output .navbar ul{display:inline-block;white-space:nowrap;line-height:inherit}.mw-parser-output .navbar-brackets::before{margin-right:-0.125em;content:"[ "}.mw-parser-output .navbar-brackets::after{margin-left:-0.125em;content:" ]"}.mw-parser-output .navbar li{word-spacing:-0.125em}.mw-parser-output .navbar a>span,.mw-parser-output .navbar a>abbr{text-decoration:inherit}.mw-parser-output .navbar-mini abbr{font-variant:small-caps;border-bottom:none;text-decoration:none;cursor:inherit}.mw-parser-output .navbar-ct-full{font-size:114%;margin:0 7em}.mw-parser-output .navbar-ct-mini{font-size:114%;margin:0 4em}html.skin-theme-clientpref-night .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}@media(prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}}@media print{.mw-parser-output .navbar{display:none!important}}</style><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Evolution" title="Template:Evolution"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Evolution" title="Template talk:Evolution"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Evolution" title="Special:EditPage/Template:Evolution"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Evolutionary_biology753" style="font-size:114%;margin:0 4em"><a href="/wiki/Evolutionary_biology" title="Evolutionary biology">Evolutionary biology</a></div></th></tr><tr><td class="navbox-abovebelow" colspan="2"><div> <ul><li><a href="/wiki/Introduction_to_evolution" title="Introduction to evolution">Introduction</a></li> <li><a href="/wiki/Outline_of_evolution" title="Outline of evolution">Outline</a></li> <li><a href="/wiki/Timeline_of_the_evolutionary_history_of_life" title="Timeline of the evolutionary history of life">Timeline of evolution</a></li> <li><a href="/wiki/History_of_life" title="History of life">History of life</a></li> <li><a href="/wiki/Index_of_evolutionary_biology_articles" title="Index of evolutionary biology articles">Index</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Evolution" title="Evolution">Evolution</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Abiogenesis" title="Abiogenesis">Abiogenesis</a></li> <li><a href="/wiki/Adaptation" title="Adaptation">Adaptation</a></li> <li><a href="/wiki/Adaptive_radiation" title="Adaptive radiation">Adaptive radiation</a></li> <li><a class="mw-selflink selflink">Altruism</a> <ul><li><a href="/wiki/Cheating_(biology)" title="Cheating (biology)">Cheating</a></li> <li><a href="/wiki/Reciprocal_altruism" title="Reciprocal altruism">Reciprocal</a></li></ul></li> <li><a href="/wiki/Baldwin_effect" title="Baldwin effect">Baldwin effect</a></li> <li><a href="/wiki/Cladistics" title="Cladistics">Cladistics</a></li> <li><a href="/wiki/Coevolution" title="Coevolution">Coevolution</a> <ul><li><a href="/wiki/Mutualism_(biology)" title="Mutualism (biology)">Mutualism</a></li></ul></li> <li><a href="/wiki/Common_descent" title="Common descent">Common descent</a></li> <li><a href="/wiki/Convergent_evolution" title="Convergent evolution">Convergence</a></li> <li><a href="/wiki/Divergent_evolution" title="Divergent evolution">Divergence</a></li> <li><a href="/wiki/Earliest_known_life_forms" title="Earliest known life forms">Earliest known life forms</a></li> <li><a href="/wiki/Evidence_of_common_descent" title="Evidence of common descent">Evidence of evolution</a></li> <li><a href="/wiki/Evolutionary_arms_race" title="Evolutionary arms race">Evolutionary arms race</a></li> <li><a href="/wiki/Evolutionary_pressure" title="Evolutionary pressure">Evolutionary pressure</a></li> <li><a href="/wiki/Exaptation" title="Exaptation">Exaptation</a></li> <li><a href="/wiki/Extinction" title="Extinction">Extinction</a> <ul><li><a href="/wiki/Extinction_event" title="Extinction event">Event</a></li></ul></li> <li><a href="/wiki/Homology_(biology)" title="Homology (biology)">Homology</a></li> <li><a href="/wiki/Last_universal_common_ancestor" title="Last universal common ancestor">Last universal common ancestor</a></li> <li><a href="/wiki/Macroevolution" title="Macroevolution">Macroevolution</a></li> <li><a href="/wiki/Microevolution" title="Microevolution">Microevolution</a></li> <li><a href="/wiki/Evolutionary_mismatch" title="Evolutionary mismatch">Mismatch</a></li> <li><a href="/wiki/Nonadaptive_radiation" title="Nonadaptive radiation">Non-adaptive radiation</a></li> <li><a href="/wiki/Abiogenesis" title="Abiogenesis">Origin of life</a></li> <li><a href="/wiki/Panspermia" title="Panspermia">Panspermia</a></li> <li><a href="/wiki/Parallel_evolution" title="Parallel evolution">Parallel evolution</a></li> <li><a href="/wiki/Signalling_theory" title="Signalling theory">Signalling theory</a> <ul><li><a href="/wiki/Handicap_principle" title="Handicap principle">Handicap principle</a></li></ul></li> <li><a href="/wiki/Speciation" title="Speciation">Speciation</a> <ul><li><a href="/wiki/Species" title="Species">Species</a></li> <li><a href="/wiki/Species_complex" title="Species complex">Species complex</a></li></ul></li> <li><a href="/wiki/Evolutionary_taxonomy" title="Evolutionary taxonomy">Taxonomy</a></li> <li><a href="/wiki/Unit_of_selection" title="Unit of selection">Unit of selection</a> <ul><li><a href="/wiki/Gene-centered_view_of_evolution" title="Gene-centered view of evolution">Gene-centered view of evolution</a></li></ul></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Population_genetics" title="Population genetics">Population<br />genetics</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Selective_breeding" title="Selective breeding">Artificial selection</a></li> <li><a href="/wiki/Biodiversity" title="Biodiversity">Biodiversity</a></li> <li><a href="/wiki/Evolutionarily_stable_strategy" title="Evolutionarily stable strategy">Evolutionarily stable strategy</a></li> <li><a href="/wiki/Fisher%27s_principle" title="Fisher's principle">Fisher's principle</a></li> <li><a href="/wiki/Fitness_(biology)" title="Fitness (biology)">Fitness</a> <ul><li><a href="/wiki/Inclusive_fitness" title="Inclusive fitness">Inclusive</a></li></ul></li> <li><a href="/wiki/Gene_flow" title="Gene flow">Gene flow</a></li> <li><a href="/wiki/Genetic_drift" title="Genetic drift">Genetic drift</a></li> <li><a href="/wiki/Kin_selection" title="Kin selection">Kin selection</a> <ul><li><a href="/wiki/Parental_investment" title="Parental investment">Parental investment</a></li> <li><a href="/wiki/Parent%E2%80%93offspring_conflict" title="Parent–offspring conflict">Parent–offspring conflict</a></li></ul></li> <li><a href="/wiki/Mutation" title="Mutation">Mutation</a></li> <li><a href="/wiki/Population" title="Population">Population</a></li> <li><a href="/wiki/Natural_selection" title="Natural selection">Natural selection</a></li> <li><a href="/wiki/Sexual_dimorphism" title="Sexual dimorphism">Sexual dimorphism</a></li> <li><a href="/wiki/Sexual_selection" title="Sexual selection">Sexual selection</a> <ul><li><a href="/wiki/Sexual_selection_in_flowering_plants" title="Sexual selection in flowering plants">Flowering plants</a></li> <li><a href="/wiki/Sexual_selection_in_fungi" title="Sexual selection in fungi">Fungi</a></li> <li><a href="/wiki/Mate_choice" title="Mate choice">Mate choice</a></li></ul></li> <li><a href="/wiki/Social_selection" title="Social selection">Social selection</a></li> <li><a href="/wiki/Trivers%E2%80%93Willard_hypothesis" title="Trivers–Willard hypothesis">Trivers–Willard hypothesis</a></li> <li><a href="/wiki/Genetic_variation" title="Genetic variation">Variation</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Development</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Canalisation_(genetics)" title="Canalisation (genetics)">Canalisation</a></li> <li><a href="/wiki/Evolutionary_developmental_biology" title="Evolutionary developmental biology">Evolutionary developmental biology</a></li> <li><a href="/wiki/Genetic_assimilation" title="Genetic assimilation">Genetic assimilation</a></li> <li><a href="/wiki/Inversion_(evolutionary_biology)" title="Inversion (evolutionary biology)">Inversion</a></li> <li><a href="/wiki/Modularity_(biology)" title="Modularity (biology)">Modularity</a></li> <li><a href="/wiki/Phenotypic_plasticity" title="Phenotypic plasticity">Phenotypic plasticity</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Of <a href="/wiki/Taxon" title="Taxon">taxa</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Evolution_of_bacteria" title="Evolution of bacteria">Bacteria</a></li> <li><a href="/wiki/Evolution_of_birds" title="Evolution of birds">Birds</a> <ul><li><a href="/wiki/Origin_of_birds" title="Origin of birds">origin</a></li></ul></li> <li><a href="/wiki/Evolution_of_brachiopods" title="Evolution of brachiopods">Brachiopods</a></li> <li><a href="/wiki/Evolution_of_molluscs" title="Evolution of molluscs">Molluscs</a> <ul><li><a href="/wiki/Evolution_of_cephalopods" title="Evolution of cephalopods">Cephalopods</a></li></ul></li> <li><a href="/wiki/Dinosaur#Evolutionary_history" title="Dinosaur">Dinosaurs</a></li> <li><a href="/wiki/Evolution_of_fish" title="Evolution of fish">Fish</a></li> <li><a href="/wiki/Evolution_of_fungi" title="Evolution of fungi">Fungi</a></li> <li><a href="/wiki/Evolution_of_insects" title="Evolution of insects">Insects</a> <ul><li><a href="/wiki/Evolution_of_butterflies" title="Evolution of butterflies">butterflies</a></li></ul></li> <li><a href="/wiki/History_of_life" title="History of life">Life</a></li> <li><a href="/wiki/Evolution_of_mammals" title="Evolution of mammals">Mammals</a> <ul><li><a href="/wiki/Cat_gap" title="Cat gap">cats</a></li> <li><a href="/wiki/Canidae#Evolution" title="Canidae">canids</a> <ul><li><a href="/wiki/Evolution_of_the_wolf" title="Evolution of the wolf">wolves</a></li> <li><a href="/wiki/Domestication_of_the_dog" title="Domestication of the dog">dogs</a></li></ul></li> <li><a href="/wiki/Hyena#Evolution" title="Hyena">hyenas</a></li> <li><a href="/wiki/Evolution_of_cetaceans" title="Evolution of cetaceans">dolphins and whales</a></li> <li><a href="/wiki/Evolution_of_the_horse" title="Evolution of the horse">horses</a></li> <li><a href="/wiki/Evolution_of_Macropodidae" title="Evolution of Macropodidae">Kangaroos</a></li> <li><a href="/wiki/Evolution_of_primates" title="Evolution of primates">primates</a> <ul><li><a href="/wiki/Human_evolution" title="Human evolution">humans</a></li> <li><a href="/wiki/Evolution_of_lemurs" title="Evolution of lemurs">lemurs</a></li></ul></li> <li><a href="/wiki/Evolution_of_sirenians" title="Evolution of sirenians">sea cows</a></li></ul></li> <li><a href="/wiki/Evolutionary_history_of_plants" title="Evolutionary history of plants">Plants</a> <ul><li><a href="/wiki/Pollinator-mediated_selection" title="Pollinator-mediated selection">pollinator-mediated</a></li></ul></li> <li><a href="/wiki/Evolution_of_reptiles" title="Evolution of reptiles">Reptiles</a></li> <li><a href="/wiki/Evolution_of_spiders" title="Evolution of spiders">Spiders</a></li> <li><a href="/wiki/Evolution_of_tetrapods" title="Evolution of tetrapods">Tetrapods</a></li> <li><a href="/wiki/Viral_evolution" title="Viral evolution">Viruses</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Of <a href="/wiki/Organ_(anatomy)" class="mw-redirect" title="Organ (anatomy)">organs</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Evolution_of_cells" title="Evolution of cells">Cell</a></li> <li><a href="/wiki/Models_of_DNA_evolution" title="Models of DNA evolution">DNA</a></li> <li><a href="/wiki/Evolution_of_flagella" title="Evolution of flagella">Flagella</a></li> <li><a href="/wiki/Eukaryote#Origin_of_eukaryotes" title="Eukaryote">Eukaryotes</a> <ul><li><a href="/wiki/Symbiogenesis" title="Symbiogenesis">symbiogenesis</a></li> <li><a href="/wiki/Chromosome#Eukaryotes" title="Chromosome">chromosome</a></li> <li><a href="/wiki/Endomembrane_system#Evolution" title="Endomembrane system">endomembrane system</a></li> <li><a href="/wiki/Mitochondrion#Origin_and_evolution" title="Mitochondrion">mitochondria</a></li> <li><a href="/wiki/Cell_nucleus#Evolution" title="Cell nucleus">nucleus</a></li> <li><a href="/wiki/Plastid#Origin" title="Plastid">plastids</a></li></ul></li> <li>In animals <ul><li><a href="/wiki/Evolution_of_the_eye" title="Evolution of the eye">eye</a></li> <li><a href="/wiki/Hair#Evolution" title="Hair">hair</a></li> <li><a href="/wiki/Evolution_of_mammalian_auditory_ossicles" title="Evolution of mammalian auditory ossicles">auditory ossicle</a></li> <li><a href="/wiki/Evolution_of_nervous_systems" title="Evolution of nervous systems">nervous system</a></li> <li><a href="/wiki/Evolution_of_the_brain" title="Evolution of the brain">brain</a></li></ul></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Of <a href="/wiki/Biological_process" title="Biological process">processes</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Evolution_of_ageing" title="Evolution of ageing">Aging</a> <ul><li><a href="/wiki/Death#Evolution_of_aging_and_mortality" title="Death">Death</a></li> <li><a href="/wiki/Programmed_cell_death#Evolutionary_origin_of_mitochondrial_apoptosis" title="Programmed cell death">Programmed cell death</a></li></ul></li> <li><a href="/wiki/Origin_of_avian_flight" title="Origin of avian flight">Avian flight</a></li> <li><a href="/wiki/Evolution_of_biological_complexity" title="Evolution of biological complexity">Biological complexity</a></li> <li><a href="/wiki/Cooperation_(evolution)" title="Cooperation (evolution)">Cooperation</a></li> <li><a href="/wiki/Evolution_of_color_vision" title="Evolution of color vision">Color vision</a> <ul><li><a href="/wiki/Evolution_of_color_vision_in_primates" title="Evolution of color vision in primates">in primates</a></li></ul></li> <li><a href="/wiki/Evolution_of_emotion" title="Evolution of emotion">Emotion</a></li> <li><a href="/wiki/Empathy#Evolution_across_species" title="Empathy">Empathy</a></li> <li><a href="/wiki/Evolutionary_ethics" title="Evolutionary ethics">Ethics</a></li> <li><a href="/wiki/Evolution_of_eusociality" title="Evolution of eusociality">Eusociality</a></li> <li><a href="/wiki/Immune_system#Evolution_and_other_mechanisms" title="Immune system">Immune system</a></li> <li><a href="/wiki/Metabolism#Evolution" title="Metabolism">Metabolism</a></li> <li><a href="/wiki/Monogamy_in_animals" title="Monogamy in animals">Monogamy</a></li> <li><a href="/wiki/Evolution_of_morality" title="Evolution of morality">Morality</a></li> <li><a href="/wiki/Mosaic_evolution" title="Mosaic evolution">Mosaic evolution</a></li> <li><a href="/wiki/Multicellular_organism#Evolutionary_history" title="Multicellular organism">Multicellularity</a></li> <li><a href="/wiki/Evolution_of_sexual_reproduction" title="Evolution of sexual reproduction">Sexual reproduction</a> <ul><li><a href="/wiki/Anisogamy#Evolution" title="Anisogamy">Gamete differentiation/sexes</a></li> <li><a href="/wiki/Biological_life_cycle" title="Biological life cycle">Life cycles/nuclear phases</a></li> <li><a href="/wiki/Mating_type" title="Mating type">Mating types</a></li> <li><a href="/wiki/Origin_and_function_of_meiosis" title="Origin and function of meiosis">Meiosis</a></li> <li><a href="/wiki/Sex-determination_system#Evolution" title="Sex-determination system">Sex-determination</a></li></ul></li> <li><a href="/wiki/Evolution_of_snake_venom" title="Evolution of snake venom">Snake venom</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Tempo_and_Mode_in_Evolution" title="Tempo and Mode in Evolution">Tempo and modes</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Phyletic_gradualism" title="Phyletic gradualism">Gradualism</a>/<a href="/wiki/Punctuated_equilibrium" title="Punctuated equilibrium">Punctuated equilibrium</a>/<a href="/wiki/Saltation_(biology)" title="Saltation (biology)">Saltationism</a></li> <li><a href="/wiki/Point_mutation" title="Point mutation">Micromutation</a>/<a href="/wiki/Mutationism#Later_mutationist_theories" title="Mutationism">Macromutation</a></li> <li><a href="/wiki/Uniformitarianism" title="Uniformitarianism">Uniformitarianism</a>/<a href="/wiki/Catastrophism" title="Catastrophism">Catastrophism</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Speciation" title="Speciation">Speciation</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Allopatric_speciation" title="Allopatric speciation">Allopatric</a></li> <li><a href="/wiki/Anagenesis" title="Anagenesis">Anagenesis</a></li> <li><a href="/wiki/Catagenesis_(biology)" title="Catagenesis (biology)">Catagenesis</a></li> <li><a href="/wiki/Cladogenesis" title="Cladogenesis">Cladogenesis</a></li> <li><a href="/wiki/Cospeciation" title="Cospeciation">Cospeciation</a></li> <li><a href="/wiki/Ecological_speciation" title="Ecological speciation">Ecological</a></li> <li><a href="/wiki/Hybrid_speciation" title="Hybrid speciation">Hybrid</a></li> <li><a href="/wiki/Nonecological_speciation" title="Nonecological speciation">Non-ecological</a></li> <li><a href="/wiki/Parapatric_speciation" title="Parapatric speciation">Parapatric</a></li> <li><a href="/wiki/Peripatric_speciation" title="Peripatric speciation">Peripatric</a></li> <li><a href="/wiki/Reinforcement_(speciation)" title="Reinforcement (speciation)">Reinforcement</a></li> <li><a href="/wiki/Sympatric_speciation" title="Sympatric speciation">Sympatric</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/History_of_evolutionary_thought" title="History of evolutionary thought">History</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Evolutionary_ideas_of_the_Renaissance_and_Enlightenment" title="Evolutionary ideas of the Renaissance and Enlightenment">Renaissance and Enlightenment</a></li> <li><a href="/wiki/Transmutation_of_species" title="Transmutation of species">Transmutation of species</a></li> <li><a href="/wiki/David_Hume" title="David Hume">David Hume</a> <ul><li><i><a href="/wiki/Dialogues_Concerning_Natural_Religion" title="Dialogues Concerning Natural Religion">Dialogues Concerning Natural Religion</a></i></li></ul></li> <li><a href="/wiki/Charles_Darwin" title="Charles Darwin">Charles Darwin</a> <ul><li><i><a href="/wiki/On_the_Origin_of_Species" title="On the Origin of Species">On the Origin of Species</a></i></li></ul></li> <li><a href="/wiki/History_of_paleontology" title="History of paleontology">History of paleontology</a></li> <li><a href="/wiki/Transitional_fossil" title="Transitional fossil">Transitional fossil</a></li> <li><a href="/wiki/Blending_inheritance" title="Blending inheritance">Blending inheritance</a></li> <li><a href="/wiki/Mendelian_inheritance" title="Mendelian inheritance">Mendelian inheritance</a></li> <li><a href="/wiki/The_eclipse_of_Darwinism" title="The eclipse of Darwinism">The eclipse of Darwinism</a></li> <li><a href="/wiki/Neo-Darwinism" title="Neo-Darwinism">Neo-Darwinism</a></li> <li><a href="/wiki/Modern_synthesis_(20th_century)" title="Modern synthesis (20th century)">Modern synthesis</a></li> <li><a href="/wiki/History_of_molecular_evolution" title="History of molecular evolution">History of molecular evolution</a></li> <li><a href="/wiki/Extended_evolutionary_synthesis" title="Extended evolutionary synthesis">Extended evolutionary synthesis</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Philosophy</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Darwinism" title="Darwinism">Darwinism</a></li> <li><a href="/wiki/Alternatives_to_Darwinian_evolution" title="Alternatives to Darwinian evolution">Alternatives</a> <ul><li><a href="/wiki/Catastrophism" title="Catastrophism">Catastrophism</a></li> <li><a href="/wiki/Lamarckism" title="Lamarckism">Lamarckism</a></li> <li><a href="/wiki/Orthogenesis" title="Orthogenesis">Orthogenesis</a></li> <li><a href="/wiki/Mutationism" title="Mutationism">Mutationism</a></li> <li><a href="/wiki/Saltation_(biology)" title="Saltation (biology)">Saltationism</a></li> <li><a href="/wiki/Structuralism_(biology)" title="Structuralism (biology)">Structuralism</a> <ul><li><a href="/wiki/Spandrel_(biology)" title="Spandrel (biology)">Spandrel</a></li></ul></li> <li><a href="/wiki/Theistic_evolution" title="Theistic evolution">Theistic</a></li> <li><a href="/wiki/Vitalism" title="Vitalism">Vitalism</a></li></ul></li> <li><a href="/wiki/Teleology_in_biology" title="Teleology in biology">Teleology in biology</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Related</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Biogeography" title="Biogeography">Biogeography</a></li> <li><a href="/wiki/Ecological_genetics" title="Ecological genetics">Ecological genetics</a></li> <li><a href="/wiki/Evolutionary_medicine" title="Evolutionary medicine">Evolutionary medicine</a></li> <li><a href="/wiki/Group_selection" title="Group selection">Group selection</a> <ul><li><a href="/wiki/Cultural_evolution" title="Cultural evolution">Cultural evolution</a></li> <li><a href="/wiki/Cultural_group_selection" title="Cultural group selection">Cultural group selection</a></li> <li><a href="/wiki/Dual_inheritance_theory" title="Dual inheritance theory">Dual inheritance theory</a></li></ul></li> <li><a href="/wiki/Hologenome_theory_of_evolution" title="Hologenome theory of evolution">Hologenome theory of evolution</a></li> <li><a href="/wiki/Missing_heritability_problem" title="Missing heritability problem">Missing heritability problem</a></li> <li><a href="/wiki/Molecular_evolution" title="Molecular evolution">Molecular evolution</a></li> <li><a href="/wiki/Astrobiology" title="Astrobiology">Astrobiology</a></li> <li><a href="/wiki/Phylogenetics" title="Phylogenetics">Phylogenetics</a> <ul><li><a href="/wiki/Phylogenetic_tree" title="Phylogenetic tree">Tree</a></li></ul></li> <li><a href="/wiki/Polymorphism_(biology)" title="Polymorphism (biology)">Polymorphism</a></li> <li><a href="/wiki/Protocell" title="Protocell">Protocell</a></li> <li><a href="/wiki/Systematics" title="Systematics">Systematics</a></li> <li><a href="/wiki/Transgenerational_epigenetic_inheritance" title="Transgenerational epigenetic inheritance">Transgenerational epigenetic inheritance</a></li></ul> </div></td></tr><tr><td class="navbox-abovebelow" colspan="2"><div> <ul><li><span class="noviewer" typeof="mw:File"><span title="Category"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/16px-Symbol_category_class.svg.png" decoding="async" width="16" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/23px-Symbol_category_class.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/31px-Symbol_category_class.svg.png 2x" data-file-width="180" data-file-height="185" /></span></span> <a href="/wiki/Category:Evolutionary_biology" title="Category:Evolutionary biology">Category</a></li> <li><span class="noviewer" typeof="mw:File"><a href="/wiki/File:Symbol_portal_class.svg" class="mw-file-description" title="Portal"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/e/e2/Symbol_portal_class.svg/20px-Symbol_portal_class.svg.png" decoding="async" width="16" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/e/e2/Symbol_portal_class.svg/40px-Symbol_portal_class.svg.png 1.5x" data-file-width="180" data-file-height="185" /></a></span> <a href="/wiki/Portal:Evolutionary_biology" title="Portal:Evolutionary biology">Portal</a></li></ul> </div></td></tr></tbody></table></div> <div class="navbox-styles"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374" /><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236075235" /></div><div role="navigation" class="navbox" aria-labelledby="Ethology159" style="padding:3px"><table class="nowraplinks hlist mw-collapsible autocollapse navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="col" class="navbox-title" colspan="2"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374" /><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239400231" /><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Ethology" title="Template:Ethology"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Ethology" title="Template talk:Ethology"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Ethology" title="Special:EditPage/Template:Ethology"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Ethology159" style="font-size:114%;margin:0 4em"><a href="/wiki/Ethology" title="Ethology">Ethology</a></div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%">Branches</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Animal_cognition" title="Animal cognition">Animal cognition</a></li> <li><a href="/wiki/Animal_communication" title="Animal communication">Animal communication</a></li> <li><a href="/wiki/Animal_consciousness" title="Animal consciousness">Animal consciousness</a></li> <li><a href="/wiki/Animal_culture" title="Animal culture">Animal culture</a></li> <li><a href="/wiki/Animal_sexual_behaviour" title="Animal sexual behaviour">Animal sexual behaviour</a></li> <li><a href="/wiki/Animal_welfare_science" title="Animal welfare science">Animal welfare science</a></li> <li><a href="/wiki/Anthrozoology" title="Anthrozoology">Anthrozoology</a></li> <li><a href="/wiki/Bee_learning_and_communication" title="Bee learning and communication">Bee learning and communication</a></li> <li><a href="/wiki/Behavioral_ecology" title="Behavioral ecology">Behavioural ecology</a></li> <li><a href="/wiki/Behavioral_endocrinology" title="Behavioral endocrinology">Behavioral endocrinology</a></li> <li><a href="/wiki/Behavioural_genetics" title="Behavioural genetics">Behavioural genetics</a></li> <li><a href="/wiki/Breed" title="Breed">Breed</a></li> <li><a href="/wiki/Cognitive_ethology" title="Cognitive ethology">Cognitive ethology</a></li> <li><a href="/wiki/Comfort_behaviour_in_animals" title="Comfort behaviour in animals">Comfort behaviour</a> <ul><li><a href="/wiki/Personal_grooming" title="Personal grooming">Grooming</a></li></ul></li> <li><a href="/wiki/Comparative_psychology" title="Comparative psychology">Comparative psychology</a></li> <li><a href="/wiki/Emotion_in_animals" title="Emotion in animals">Emotion in animals</a></li> <li><a href="/wiki/Ethogram" title="Ethogram">Ethogram</a></li> <li><a href="/wiki/Evolutionary_neuroscience" title="Evolutionary neuroscience">Evolutionary neuroscience</a></li> <li><a href="/wiki/List_of_feeding_behaviours" title="List of feeding behaviours">Feeding</a></li> <li><a href="/wiki/Hover_(behaviour)" title="Hover (behaviour)">Hover</a></li> <li><a href="/wiki/Human_ethology" title="Human ethology">Human ethology</a></li> <li><a href="/wiki/Instinct" title="Instinct">Instinct</a></li> <li><a href="/wiki/Learning" title="Learning">Learning</a></li> <li><a href="/wiki/Neuroethology" title="Neuroethology">Neuroethology</a></li> <li><a href="/wiki/Pain_in_animals" title="Pain in animals">Pain in animals</a></li> <li><a href="/wiki/Philosophical_ethology" title="Philosophical ethology">Philosophical ethology</a></li> <li><a href="/wiki/Sociobiology" title="Sociobiology">Sociobiology</a></li> <li><a href="/wiki/Stereotypy_(non-human)" title="Stereotypy (non-human)">Stereotypy</a></li> <li><a href="/wiki/Structures_built_by_animals" title="Structures built by animals">Structures</a> <ul><li><a href="/wiki/Beehive" title="Beehive">Hive</a></li> <li><a href="/wiki/Honeycomb_structure" title="Honeycomb structure">Honeycomb</a></li> <li><a href="/wiki/Nest" title="Nest">Nest</a></li> <li><a href="/wiki/Nesting_instinct" title="Nesting instinct">Instinct</a></li></ul></li> <li><a href="/wiki/Swarm_behaviour" title="Swarm behaviour">Swarm</a></li> <li><a href="/wiki/Tool_use_by_non-humans" title="Tool use by non-humans">Tool use by non-humans</a></li> <li><a href="/wiki/Zoosemiotics" title="Zoosemiotics">Zoosemiotics</a></li> <li><a href="/wiki/Zoomusicology" title="Zoomusicology">Zoomusicology</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Ethologists</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Patrick_Bateson" title="Patrick Bateson">Patrick Bateson</a></li> <li><a href="/wiki/Marc_Bekoff" title="Marc Bekoff">Marc Bekoff</a></li> <li><a href="/wiki/Donald_Broom" title="Donald Broom">Donald Broom</a></li> <li><a href="/wiki/John_B._Calhoun" title="John B. Calhoun">John B. Calhoun</a></li> <li><a href="/wiki/Charles_Darwin" title="Charles Darwin">Charles Darwin</a></li> <li><a href="/wiki/Marian_Dawkins" title="Marian Dawkins">Marian Dawkins</a></li> <li><a href="/wiki/Richard_Dawkins" title="Richard Dawkins">Richard Dawkins</a></li> <li><a href="/wiki/Iren%C3%A4us_Eibl-Eibesfeldt" title="Irenäus Eibl-Eibesfeldt">Irenäus Eibl-Eibesfeldt</a></li> <li><a href="/wiki/Dian_Fossey" title="Dian Fossey">Dian Fossey</a></li> <li><a href="/wiki/Karl_von_Frisch" title="Karl von Frisch">Karl von Frisch</a></li> <li><a href="/wiki/Jane_Goodall" title="Jane Goodall">Jane Goodall</a></li> <li><a href="/wiki/Heini_Hediger" title="Heini Hediger">Heini Hediger</a></li> <li><a href="/wiki/Julian_Huxley" title="Julian Huxley">Julian Huxley</a></li> <li><a href="/wiki/Konrad_Lorenz" title="Konrad Lorenz">Konrad Lorenz</a></li> <li><a href="/wiki/Desmond_Morris" title="Desmond Morris">Desmond Morris</a></li> <li><a href="/wiki/Thomas_Sebeok" title="Thomas Sebeok">Thomas Sebeok</a></li> <li><a href="/wiki/William_Homan_Thorpe" title="William Homan Thorpe">William Homan Thorpe</a></li> <li><a href="/wiki/Nikolaas_Tinbergen" title="Nikolaas Tinbergen">Nikolaas Tinbergen</a></li> <li><a href="/wiki/Jakob_von_Uexk%C3%BCll" class="mw-redirect" title="Jakob von Uexküll">Jakob von Uexküll</a></li> <li><a href="/wiki/Wolfgang_Wickler" title="Wolfgang Wickler">Wolfgang Wickler</a></li> <li><a href="/wiki/E._O._Wilson" title="E. O. Wilson">E. O. Wilson</a></li> <li><a href="/wiki/Solly_Zuckerman" class="mw-redirect" title="Solly Zuckerman">Solly Zuckerman</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Societies</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Association_for_the_Study_of_Animal_Behaviour" title="Association for the Study of Animal Behaviour">Association for the Study of Animal Behaviour</a></li> <li><a href="/wiki/International_Society_for_Applied_Ethology" title="International Society for Applied Ethology">International Society for Applied Ethology</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Journals</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><i><a href="/wiki/Animal_Behaviour_(journal)" title="Animal Behaviour (journal)">Animal Behaviour</a></i></li> <li><i><a href="/wiki/Animal_Cognition" title="Animal Cognition">Animal Cognition</a></i></li> <li><i><a href="/wiki/Animal_Welfare_(journal)" title="Animal Welfare (journal)">Animal Welfare</a></i></li> <li><i><a href="/wiki/Behavioral_Ecology_(journal)" title="Behavioral Ecology (journal)">Behavioral Ecology</a></i></li> <li><i><a href="/wiki/Behaviour_(journal)" title="Behaviour (journal)">Behaviour</a></i></li></ul> </div></td></tr><tr><td class="navbox-abovebelow" colspan="2"><div> <ul><li><span class="noviewer" typeof="mw:File"><span title="Category"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/16px-Symbol_category_class.svg.png" decoding="async" width="16" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/23px-Symbol_category_class.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/31px-Symbol_category_class.svg.png 2x" data-file-width="180" data-file-height="185" /></span></span> <a href="/wiki/Category:Ethology" title="Category:Ethology">Category</a></li></ul> </div></td></tr></tbody></table></div> <div class="navbox-styles"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374" /><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236075235" /></div><div role="navigation" class="navbox" aria-labelledby="Evolutionary_psychology1033" style="padding:3px"><table class="nowraplinks hlist mw-collapsible autocollapse navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="col" class="navbox-title" colspan="2"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374" /><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239400231" /><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Evolutionary_psychology" title="Template:Evolutionary psychology"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Evolutionary_psychology" title="Template talk:Evolutionary psychology"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Evolutionary_psychology" title="Special:EditPage/Template:Evolutionary psychology"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Evolutionary_psychology1033" style="font-size:114%;margin:0 4em"><a href="/wiki/Evolutionary_psychology" title="Evolutionary psychology">Evolutionary psychology</a></div></th></tr><tr><td class="navbox-abovebelow" colspan="2"><div> <ul><li><a href="/wiki/History_of_evolutionary_psychology" title="History of evolutionary psychology">History</a> <ul><li><a href="/wiki/History_of_evolutionary_thought" title="History of evolutionary thought">Evolutionary thought</a></li></ul></li> <li><a href="/wiki/Theoretical_foundations_of_evolutionary_psychology" title="Theoretical foundations of evolutionary psychology">Theoretical foundations</a> <ul><li><a href="/wiki/Adaptationism" title="Adaptationism">Adaptationism</a></li> <li><a href="/wiki/Cognitive_revolution" title="Cognitive revolution">Cognitive revolution</a></li> <li><a href="/wiki/Cognitivism_(psychology)" title="Cognitivism (psychology)">Cognitivism</a></li> <li><a href="/wiki/Gene-centered_view_of_evolution" title="Gene-centered view of evolution">Gene selection theory</a></li> <li><a href="/wiki/Modern_synthesis_(20th_century)" title="Modern synthesis (20th century)">Modern synthesis</a></li></ul></li> <li><a href="/wiki/Criticism_of_evolutionary_psychology" title="Criticism of evolutionary psychology">Criticism</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align:left;"><a href="/wiki/Human_evolution" title="Human evolution">Evolutionary<br />processes</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Psychological_adaptation" title="Psychological adaptation">Adaptations</a></li> <li><a class="mw-selflink selflink">Altruism</a> <ul><li><a href="/wiki/Cheating_(biology)" title="Cheating (biology)">Cheating</a></li> <li><a href="/wiki/Hamiltonian_spite" title="Hamiltonian spite">Hamiltonian spite</a></li> <li><a href="/wiki/Reciprocal_altruism_in_humans" title="Reciprocal altruism in humans">Reciprocal</a></li></ul></li> <li><a href="/wiki/Baldwin_effect" title="Baldwin effect">Baldwin effect</a></li> <li><a href="/wiki/Spandrel_(biology)" title="Spandrel (biology)">By-products</a></li> <li><a href="/wiki/Evolutionarily_stable_strategy" title="Evolutionarily stable strategy">Evolutionarily stable strategy</a></li> <li><a href="/wiki/Exaptation" title="Exaptation">Exaptation</a></li> <li><a href="/wiki/Fitness_(biology)" title="Fitness (biology)">Fitness</a> <ul><li><a href="/wiki/Inclusive_fitness_in_humans" title="Inclusive fitness in humans">Inclusive</a></li></ul></li> <li><a href="/wiki/Kin_selection" title="Kin selection">Kin selection</a></li> <li><a href="/wiki/Evolutionary_mismatch" title="Evolutionary mismatch">Mismatch</a></li> <li><a href="/wiki/Natural_selection" title="Natural selection">Natural selection</a></li> <li><a href="/wiki/Parental_investment" title="Parental investment">Parental investment</a> <ul><li><a href="/wiki/Parent%E2%80%93offspring_conflict" title="Parent–offspring conflict">Parent–offspring conflict</a></li></ul></li> <li><a href="/wiki/Sexual_selection_in_humans" title="Sexual selection in humans">Sexual selection</a> <ul><li><a href="/wiki/Costly_signaling_theory_in_evolutionary_psychology" title="Costly signaling theory in evolutionary psychology">Costly signaling</a></li> <li><a href="/wiki/Male_intrasexual_competition" title="Male intrasexual competition">Male</a>/<a href="/wiki/Female_intrasexual_competition" title="Female intrasexual competition">female intrasexual competition</a></li> <li><a href="/wiki/Mate_choice" title="Mate choice">Mate choice</a></li> <li><a href="/wiki/Sexual_dimorphism" title="Sexual dimorphism">Sexual dimorphism</a></li></ul></li> <li><a href="/wiki/Social_selection" title="Social selection">Social selection</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align:left;">Areas</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Evolution_of_cognition" title="Evolution of cognition">Cognition</a> /<br /><a href="/wiki/Evolution_of_emotion" title="Evolution of emotion">Emotion</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Affect_(psychology)" title="Affect (psychology)">Affect</a> <ul><li><a href="/wiki/Affect_display" title="Affect display">Display</a></li> <li><a href="/wiki/Display_rules" title="Display rules">Display rules</a></li> <li><a href="/wiki/Facial_expression" title="Facial expression">Facial expression</a></li></ul></li> <li><a href="/wiki/Behavioral_modernity" title="Behavioral modernity">Behavioral modernity</a></li> <li><a href="/wiki/Cognitive_module" title="Cognitive module">Cognitive module</a>/<a href="/wiki/Modularity_of_mind" title="Modularity of mind">modularity of mind</a> <ul><li><a href="/wiki/Automatic_and_controlled_processes" title="Automatic and controlled processes">Automatic and controlled processes</a></li> <li><a href="/wiki/Computational_theory_of_mind" title="Computational theory of mind">Computational theory of mind</a></li> <li><a href="/wiki/Domain-general_learning" title="Domain-general learning">Domain generality</a></li> <li><a href="/wiki/Domain_specificity" title="Domain specificity">Domain specificity</a></li> <li><a href="/wiki/Dual_process_theory" title="Dual process theory">Dual process theory</a></li></ul></li> <li><a href="/wiki/Cognitive_tradeoff_hypothesis" title="Cognitive tradeoff hypothesis">Cognitive tradeoff hypothesis</a></li> <li><a href="/wiki/Evolution_of_the_brain" title="Evolution of the brain">Evolution of the brain</a></li> <li><a href="/wiki/Evolution_of_nervous_systems" title="Evolution of nervous systems">Evolution of nervous systems</a></li> <li><a href="/wiki/Fight-or-flight_response" title="Fight-or-flight response">Fight-or-flight response</a> <ul><li><a href="/wiki/Arachnophobia" title="Arachnophobia">Arachnophobia</a></li> <li><a href="/wiki/Fear_of_falling" title="Fear of falling">Basophobia</a></li> <li><a href="/wiki/Ophidiophobia" title="Ophidiophobia">Ophidiophobia</a></li></ul></li> <li><a href="/wiki/Folk_biology" title="Folk biology">Folk biology</a>/<a href="/wiki/Folk_taxonomy" title="Folk taxonomy">taxonomy</a></li> <li><a href="/wiki/Folk_psychology" title="Folk psychology">Folk psychology</a>/<a href="/wiki/Theory_of_mind" title="Theory of mind">theory of mind</a></li> <li><a href="/wiki/Evolution_of_human_intelligence" title="Evolution of human intelligence">Intelligence</a> <ul><li><a href="/wiki/Flynn_effect" title="Flynn effect">Flynn effect</a></li> <li><a href="/wiki/Wason_selection_task" title="Wason selection task">Wason selection task</a></li></ul></li> <li><a href="/wiki/Motor_control" title="Motor control">Motor control</a>/<a href="/wiki/Motor_skill" title="Motor skill">skill</a></li> <li><a href="/wiki/Human_multitasking" title="Human multitasking">Multitasking</a></li> <li><a href="/wiki/Neuroscience_of_sleep" title="Neuroscience of sleep">Sleep</a></li> <li><a href="/wiki/Visual_perception" title="Visual perception">Visual perception</a> <ul><li><a href="/wiki/Evolution_of_color_vision_in_primates" title="Evolution of color vision in primates">Color vision</a></li> <li><a href="/wiki/Evolution_of_the_eye" title="Evolution of the eye">Eye</a></li> <li><a href="/wiki/Na%C3%AFve_physics" title="Naïve physics">Naïve physics</a></li></ul></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Evolutionary_psychology_and_culture" title="Evolutionary psychology and culture">Culture</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Evolutionary_aesthetics" title="Evolutionary aesthetics">Aesthetics</a> <ul><li><a href="/wiki/Darwinian_literary_studies" title="Darwinian literary studies">Literary criticism</a></li> <li><a href="/wiki/Evolutionary_musicology" title="Evolutionary musicology">Musicology</a></li></ul></li> <li><a href="/wiki/Evolutionary_anthropology" title="Evolutionary anthropology">Anthropology</a> <ul><li><a href="/wiki/Biological_anthropology" title="Biological anthropology">Biological</a></li></ul></li> <li><a href="/wiki/Biosocial_criminology" title="Biosocial criminology">Crime</a></li> <li><a href="/wiki/Evolutionary_linguistics" title="Evolutionary linguistics">Language</a> <ul><li><a href="/wiki/Origin_of_language" title="Origin of language">Origin</a></li> <li><a href="/wiki/Evolutionary_psychology_of_language" title="Evolutionary psychology of language">Psychology</a></li> <li><a href="/wiki/Origin_of_speech" title="Origin of speech">Speech</a></li></ul></li> <li><a href="/wiki/Evolution_of_morality" title="Evolution of morality">Morality</a> <ul><li><a href="/wiki/Moral_foundations_theory" title="Moral foundations theory">Moral foundations</a></li></ul></li> <li><a href="/wiki/Evolutionary_psychology_of_religion" title="Evolutionary psychology of religion">Religion</a> <ul><li><a href="/wiki/Evolutionary_origin_of_religions" class="mw-redirect" title="Evolutionary origin of religions">Origin</a></li></ul></li> <li><a href="/wiki/Cultural_universal" title="Cultural universal">Universals</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Evolutionary_developmental_psychology" title="Evolutionary developmental psychology">Development</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Attachment_theory" title="Attachment theory">Attachment</a></li> <li><a href="/wiki/Human_bonding" title="Human bonding">Bonding</a></li> <li><a href="/wiki/Affectional_bond" title="Affectional bond">Affectional</a>/<a href="/wiki/Maternal_bond" title="Maternal bond">maternal</a>/<a href="/wiki/Paternal_bond" title="Paternal bond">paternal bond</a></li> <li><a href="/wiki/Maternal_deprivation" title="Maternal deprivation">Caregiver deprivation</a></li> <li><a href="/wiki/Attachment_in_children" title="Attachment in children">Childhood attachment</a></li> <li><a href="/wiki/Cinderella_effect" title="Cinderella effect">Cinderella effect</a></li> <li><a href="/wiki/Cognitive_development" title="Cognitive development">Cognitive development</a></li> <li><a href="/wiki/Evolutionary_educational_psychology" title="Evolutionary educational psychology">Education</a></li> <li><a href="/wiki/Language_acquisition" title="Language acquisition">Language acquisition</a></li> <li><a href="/wiki/Personality_development" title="Personality development">Personality development</a></li> <li><a href="/wiki/Socialization" title="Socialization">Socialization</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Ergonomics" title="Ergonomics">Human factors</a> /<br /><a href="/wiki/Evolutionary_psychiatry" title="Evolutionary psychiatry">Mental health</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Cognitive_ergonomics" title="Cognitive ergonomics">Cognitive ergonomics</a> <ul><li><a href="/wiki/Computer-mediated_communication" title="Computer-mediated communication">Computer-mediated communication</a></li> <li><a href="/wiki/Engineering_psychology" title="Engineering psychology">Engineering psychology</a></li> <li><a href="/wiki/Human%E2%80%93computer_interaction" title="Human–computer interaction">Human–computer interaction</a></li> <li><a href="/wiki/Media_naturalness_theory" title="Media naturalness theory">Media naturalness theory</a></li> <li><a href="/wiki/Neuroergonomics" title="Neuroergonomics">Neuroergonomics</a></li></ul></li> <li><a href="/wiki/Evolutionary_approaches_to_depression" title="Evolutionary approaches to depression">Depression</a></li> <li><a href="/wiki/Digital_media_use_and_mental_health" title="Digital media use and mental health">Digital media use and mental health</a></li> <li><a href="/wiki/Accident-proneness" title="Accident-proneness">Hypophobia</a></li> <li><a href="/wiki/Imprinted_brain_hypothesis" title="Imprinted brain hypothesis">Imprinted brain hypothesis</a></li> <li><a href="/wiki/Mind-blindness" title="Mind-blindness">Mind-blindness</a></li> <li><a href="/wiki/Psychological_effects_of_Internet_use" title="Psychological effects of Internet use">Psychological effects of Internet use</a></li> <li><a href="/wiki/Rank_theory_of_depression" title="Rank theory of depression">Rank theory of depression</a></li> <li><a href="/wiki/Evolution_of_schizophrenia" title="Evolution of schizophrenia">Schizophrenia</a></li> <li><a href="/wiki/Screen_time" title="Screen time">Screen time</a></li> <li><a href="/wiki/Smartphones_and_pedestrian_safety" title="Smartphones and pedestrian safety">Smartphones and pedestrian safety</a></li> <li><a href="/wiki/Social_aspects_of_television" title="Social aspects of television">Social aspects of television</a></li> <li><a href="/wiki/Societal_effects_of_cars" title="Societal effects of cars">Societal effects of cars</a> <ul><li><a href="/wiki/Distracted_driving" title="Distracted driving">Distracted driving</a></li> <li><a href="/wiki/Lead%E2%80%93crime_hypothesis" title="Lead–crime hypothesis">Lead–crime hypothesis</a></li> <li><a href="/wiki/Mobile_phones_and_driving_safety" title="Mobile phones and driving safety">Mobile phones and driving safety</a></li> <li><a href="/wiki/Texting_while_driving" title="Texting while driving">Texting while driving</a></li></ul></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Sexology" title="Sexology">Sex</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Human_sexual_activity" title="Human sexual activity">Activity</a></li> <li><a href="/wiki/Attachment_in_adults" title="Attachment in adults">Adult attachment</a></li> <li><a href="/wiki/Age_disparity_in_sexual_relationships" title="Age disparity in sexual relationships">Age disparity</a></li> <li><a href="/wiki/Sexual_arousal" title="Sexual arousal">Arousal</a></li> <li><a href="/wiki/Concealed_ovulation" title="Concealed ovulation">Concealed ovulation</a></li> <li><a href="/wiki/Coolidge_effect" title="Coolidge effect">Coolidge effect</a></li> <li><a href="/wiki/Sexual_desire" title="Sexual desire">Desire</a></li> <li><a href="/wiki/Sexual_fantasy" title="Sexual fantasy">Fantasy</a></li> <li><a href="/wiki/Effects_of_hormones_on_sexual_motivation" title="Effects of hormones on sexual motivation">Hormonal motivation</a></li> <li><a href="/wiki/Sexual_jealousy" title="Sexual jealousy">Jealousy</a></li> <li><a href="/wiki/Mate_guarding_in_humans" title="Mate guarding in humans">Mate guarding</a></li> <li><a href="/wiki/Mating_preferences" title="Mating preferences">Mating preferences</a></li> <li><a href="/wiki/Human_mating_strategies" title="Human mating strategies">Mating strategies</a></li> <li><a href="/wiki/Biology_and_sexual_orientation" title="Biology and sexual orientation">Orientation</a></li> <li><a href="/wiki/Ovulatory_shift_hypothesis" title="Ovulatory shift hypothesis">Ovulatory shift hypothesis</a></li> <li><a href="/wiki/Pair_bond" title="Pair bond">Pair bond</a></li> <li><a href="/wiki/Physical_attractiveness" title="Physical attractiveness">Physical</a>/<a href="/wiki/Sexual_attraction" title="Sexual attraction">Sexual attraction</a></li> <li><a href="/wiki/Human_sexuality" title="Human sexuality">Sexuality</a>/<a href="/wiki/Human_male_sexuality" title="Human male sexuality">male</a>/<a href="/wiki/Human_female_sexuality" title="Human female sexuality">female</a></li> <li><a href="/wiki/Sexy_son_hypothesis" title="Sexy son hypothesis">Sexy son hypothesis</a></li> <li><a href="/wiki/Westermarck_effect" title="Westermarck effect">Westermarck effect</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Sex_differences_in_psychology" title="Sex differences in psychology">Sex differences</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Aggression" title="Aggression">Aggression</a></li> <li><a href="/wiki/Sex_and_gender_differences_in_autism" title="Sex and gender differences in autism">Autism</a></li> <li><a href="/wiki/Sex_differences_in_cognition" title="Sex differences in cognition">Cognition</a></li> <li><a href="/wiki/Sex_differences_in_crime" title="Sex differences in crime">Crime</a></li> <li><a href="/wiki/Sexual_division_of_labour" title="Sexual division of labour">Division of labour</a></li> <li><a href="/wiki/Sex_differences_in_emotional_intelligence" title="Sex differences in emotional intelligence">Emotional intelligence</a></li> <li><a href="/wiki/Empathising%E2%80%93systemising_theory" title="Empathising–systemising theory">Empathising–systemising theory</a></li> <li><a href="/wiki/Gender_role" title="Gender role">Gender role</a></li> <li><a href="/wiki/Sex_differences_in_intelligence" title="Sex differences in intelligence">Intelligence</a></li> <li><a href="/wiki/Sex_differences_in_memory" title="Sex differences in memory">Memory</a></li> <li><a href="/wiki/Mental_disorders_and_gender" title="Mental disorders and gender">Mental health</a></li> <li><a href="/wiki/Sex_differences_in_narcissism" title="Sex differences in narcissism">Narcissism</a></li> <li><a href="/wiki/Neuroscience_of_sex_differences" title="Neuroscience of sex differences">Neuroscience</a></li> <li><a href="/wiki/Sex_differences_in_schizophrenia" title="Sex differences in schizophrenia">Schizophrenia</a></li> <li><a href="/wiki/Substance_abuse" title="Substance abuse">Substance abuse</a></li> <li><a href="/wiki/Gender_differences_in_suicide" title="Gender differences in suicide">Suicide</a></li> <li><a href="/wiki/Variability_hypothesis" title="Variability hypothesis">Variability hypothesis</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align:left;">Related subjects</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:1%">Academic disciplines</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Behavioral_economics" title="Behavioral economics">Behavioral</a>/<a href="/wiki/Evolutionary_economics" title="Evolutionary economics">evolutionary economics</a></li> <li><a href="/wiki/Behavioral_epigenetics" title="Behavioral epigenetics">Behavioral epigenetics</a>/<a href="/wiki/Behavioural_genetics" title="Behavioural genetics">genetics</a></li> <li><a href="/wiki/Affective_neuroscience" title="Affective neuroscience">Affective</a>/<a href="/wiki/Behavioral_neuroscience" title="Behavioral neuroscience">behavioral</a>/<a href="/wiki/Cognitive_neuroscience" title="Cognitive neuroscience">cognitive</a>/<a href="/wiki/Evolutionary_neuroscience" title="Evolutionary neuroscience">evolutionary neuroscience</a></li> <li><a href="/wiki/Biocultural_anthropology" title="Biocultural anthropology">Biocultural anthropology</a></li> <li><a href="/wiki/Biolinguistics" title="Biolinguistics">Biolinguistics</a></li> <li><a href="/wiki/Biological_psychiatry" title="Biological psychiatry">Biological psychiatry</a></li> <li><a href="/wiki/Cognitive_psychology" title="Cognitive psychology">Cognitive psychology</a></li> <li><a href="/wiki/Cognitive_science" title="Cognitive science">Cognitive science</a></li> <li><a href="/wiki/Cross-cultural_psychology" title="Cross-cultural psychology">Cross-cultural psychology</a></li> <li><a href="/wiki/Ethology" title="Ethology">Ethology</a></li> <li><a href="/wiki/Evolutionary_biology" title="Evolutionary biology">Evolutionary biology</a></li> <li><a href="/wiki/Evolutionary_medicine" title="Evolutionary medicine">Evolutionary medicine</a></li> <li><a href="/wiki/Functional_psychology" title="Functional psychology">Functional psychology</a></li> <li><a href="/wiki/Neuropsychology" title="Neuropsychology">Neuropsychology</a></li> <li><a href="/wiki/Philosophy_of_mind" title="Philosophy of mind">Philosophy of mind</a></li> <li><a href="/wiki/Population_genetics" title="Population genetics">Population genetics</a></li> <li><a href="/wiki/Primatology" title="Primatology">Primatology</a></li> <li><a href="/wiki/Sociobiology" title="Sociobiology">Sociobiology</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Research topics</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Cultural_evolution" title="Cultural evolution">Cultural evolution</a></li> <li><a href="/wiki/Evolutionary_epistemology" title="Evolutionary epistemology">Evolutionary epistemology</a></li> <li><a href="/wiki/Great_ape_language" title="Great ape language">Great ape language</a></li> <li><a href="/wiki/Human%E2%80%93animal_communication" title="Human–animal communication">Human–animal communication</a></li> <li><a href="/wiki/Missing_heritability_problem" title="Missing heritability problem">Missing heritability problem</a></li> <li><a href="/wiki/Primate_cognition" title="Primate cognition">Primate cognition</a></li> <li><a href="/wiki/Unit_of_selection" title="Unit of selection">Unit of selection</a> <ul><li><a href="/wiki/Coevolution" title="Coevolution">Coevolution</a></li> <li><a href="/wiki/Cultural_group_selection" title="Cultural group selection">Cultural group selection</a></li> <li><a href="/wiki/Dual_inheritance_theory" title="Dual inheritance theory">Dual inheritance theory</a></li> <li><a href="/wiki/Fisher%27s_principle" title="Fisher's principle">Fisher's principle</a></li> <li><a href="/wiki/Group_selection" title="Group selection">Group selection</a></li> <li><a href="/wiki/Hologenome_theory_of_evolution" title="Hologenome theory of evolution">Hologenome theory</a></li> <li><a href="/wiki/Lamarckism" title="Lamarckism">Lamarckism</a>/<a href="/wiki/Acquired_characteristic" title="Acquired characteristic">acquired characteristics</a></li> <li><a href="/wiki/Population" title="Population">Population</a></li> <li><a href="/wiki/Punctuated_equilibrium" title="Punctuated equilibrium">Punctuated equilibrium</a></li> <li><a href="/wiki/Recent_human_evolution" title="Recent human evolution">Recent human evolution</a></li> <li><a href="/wiki/Species" title="Species">Species</a></li> <li><a href="/wiki/Species_complex" title="Species complex">Species complex</a></li> <li><a href="/wiki/Transgenerational_epigenetic_inheritance" title="Transgenerational epigenetic inheritance">Transgenerational epigenetic inheritance</a></li> <li><a href="/wiki/Trivers%E2%80%93Willard_hypothesis" title="Trivers–Willard hypothesis">Trivers–Willard hypothesis</a></li></ul></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Theoretical positions</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Cultural_selection_theory" title="Cultural selection theory">Cultural selection theory</a></li> <li><a href="/wiki/Determinism" title="Determinism">Determinism</a>/<a href="/wiki/Indeterminism" title="Indeterminism">indeterminism</a> <ul><li><a href="/wiki/Biological_determinism" title="Biological determinism">Biological determinism</a></li> <li><a href="/wiki/Connectionism" title="Connectionism">Connectionism</a></li> <li><a href="/wiki/Cultural_determinism" title="Cultural determinism">Cultural determinism</a></li> <li><a href="/wiki/Environmental_determinism" title="Environmental determinism">Environmental determinism</a></li> <li><a href="/wiki/Nature_versus_nurture" title="Nature versus nurture">Nature versus nurture</a></li> <li><a href="/wiki/Psychological_nativism" title="Psychological nativism">Psychological nativism</a></li> <li><a href="/wiki/Social_constructionism" title="Social constructionism">Social constructionism</a></li> <li><a href="/wiki/Social_determinism" title="Social determinism">Social determinism</a></li> <li><a href="/wiki/Standard_social_science_model" title="Standard social science model">Standard social science model</a></li></ul></li> <li><a href="/wiki/Functionalism_(philosophy_of_mind)" title="Functionalism (philosophy of mind)">Functionalism</a></li> <li><a href="/wiki/Memetics" title="Memetics">Memetics</a></li> <li><a href="/wiki/Multilineal_evolution" title="Multilineal evolution">Multilineal evolution</a></li> <li><a href="/wiki/Neo-Darwinism" title="Neo-Darwinism">Neo-Darwinism</a></li> <li><a href="/wiki/Neoevolutionism" title="Neoevolutionism">Neoevolutionism</a></li> <li><a href="/wiki/Sociocultural_evolution" title="Sociocultural evolution">Sociocultural evolution</a></li> <li><a href="/wiki/Unilineal_evolution" title="Unilineal evolution">Unilineal evolution</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><td class="navbox-abovebelow" colspan="2"><div> <ul><li><b><a href="/wiki/List_of_evolutionary_psychologists" title="List of evolutionary psychologists">Evolutionary psychologists</a></b></li> <li><span class="noviewer" typeof="mw:File"><span title="Category"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/16px-Symbol_category_class.svg.png" decoding="async" width="16" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/23px-Symbol_category_class.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/31px-Symbol_category_class.svg.png 2x" data-file-width="180" data-file-height="185" /></span></span> <b><a href="/wiki/Category:Evolutionary_psychology" title="Category:Evolutionary psychology">Evolutionary psychology</a></b></li> <li><span class="noviewer" typeof="mw:File"><a href="/wiki/File:Symbol_portal_class.svg" class="mw-file-description" title="Portal"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/e/e2/Symbol_portal_class.svg/20px-Symbol_portal_class.svg.png" decoding="async" width="16" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/e/e2/Symbol_portal_class.svg/40px-Symbol_portal_class.svg.png 1.5x" data-file-width="180" data-file-height="185" /></a></span> <b><a href="/wiki/Portal:Psychology" title="Portal:Psychology">Psychology portal</a></b></li> <li><span class="noviewer" typeof="mw:File"><a href="/wiki/File:Symbol_portal_class.svg" class="mw-file-description" title="Portal"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/e/e2/Symbol_portal_class.svg/20px-Symbol_portal_class.svg.png" decoding="async" width="16" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/e/e2/Symbol_portal_class.svg/40px-Symbol_portal_class.svg.png 1.5x" data-file-width="180" data-file-height="185" /></a></span> <b><a href="/wiki/Portal:Evolutionary_biology" title="Portal:Evolutionary biology">Evolutionary biology portal</a></b></li></ul> </div></td></tr></tbody></table></div> <div class="navbox-styles"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374" /><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236075235" /></div><div role="navigation" class="navbox authority-control" aria-label="Navbox506" style="padding:3px"><table class="nowraplinks hlist navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Help:Authority_control" title="Help:Authority control">Authority control databases</a>: National <span class="mw-valign-text-top noprint" typeof="mw:File/Frameless"><a href="https://www.wikidata.org/wiki/Q2559380#identifiers" title="Edit this at Wikidata"><img alt="Edit this at Wikidata" src="//upload.wikimedia.org/wikipedia/en/thumb/8/8a/OOjs_UI_icon_edit-ltr-progressive.svg/10px-OOjs_UI_icon_edit-ltr-progressive.svg.png" decoding="async" width="10" height="10" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/8/8a/OOjs_UI_icon_edit-ltr-progressive.svg/15px-OOjs_UI_icon_edit-ltr-progressive.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/8/8a/OOjs_UI_icon_edit-ltr-progressive.svg/20px-OOjs_UI_icon_edit-ltr-progressive.svg.png 2x" data-file-width="20" data-file-height="20" /></a></span></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"><ul><li><span class="uid"><a rel="nofollow" class="external text" href="https://id.loc.gov/authorities/sh85003946">United States</a></span></li><li><span class="uid"><a rel="nofollow" class="external text" href="https://www.nli.org.il/en/authorities/987007294751105171">Israel</a></span></li></ul></div></td></tr></tbody></table></div>    </div><noscript><img src="https://login.wikimedia.org/wiki/Special:CentralAutoLogin/start?useformat=desktop&type=1x1&usesul3=0" alt="" width="1" height="1" style="border: none; position: absolute;"></noscript> <div class="printfooter" data-nosnippet="">Retrieved from "<a dir="ltr" href="https://en.wikipedia.org/w/index.php?title=Altruism_(biology)&oldid=1282159263">https://en.wikipedia.org/w/index.php?title=Altruism_(biology)&oldid=1282159263</a>"</div></div> <div id="catlinks" class="catlinks" data-mw="interface"><div id="mw-normal-catlinks" class="mw-normal-catlinks"><a href="/wiki/Help:Category" title="Help:Category">Categories</a>: <ul><li><a href="/wiki/Category:Behavioral_ecology" title="Category:Behavioral ecology">Behavioral ecology</a></li><li><a href="/wiki/Category:Ethology" title="Category:Ethology">Ethology</a></li><li><a href="/wiki/Category:Altruism" title="Category:Altruism">Altruism</a></li><li><a href="/wiki/Category:Evolutionary_psychology" title="Category:Evolutionary psychology">Evolutionary psychology</a></li></ul></div><div id="mw-hidden-catlinks" class="mw-hidden-catlinks mw-hidden-cats-hidden">Hidden categories: <ul><li><a href="/wiki/Category:CS1_German-language_sources_(de)" title="Category:CS1 German-language sources (de)">CS1 German-language sources (de)</a></li><li><a href="/wiki/Category:Webarchive_template_wayback_links" title="Category:Webarchive template wayback links">Webarchive template wayback links</a></li><li><a href="/wiki/Category:Articles_with_short_description" title="Category:Articles with short description">Articles with short description</a></li><li><a href="/wiki/Category:Short_description_is_different_from_Wikidata" title="Category:Short description is different from Wikidata">Short description is different from Wikidata</a></li><li><a href="/wiki/Category:Use_mdy_dates_from_February_2015" title="Category:Use mdy dates from February 2015">Use mdy dates from February 2015</a></li><li><a href="/wiki/Category:Wikipedia_articles_needing_clarification_from_August_2014" title="Category:Wikipedia articles needing clarification from August 2014">Wikipedia articles needing clarification from August 2014</a></li><li><a href="/wiki/Category:All_articles_with_unsourced_statements" title="Category:All articles with unsourced statements">All articles with unsourced statements</a></li><li><a href="/wiki/Category:Articles_with_unsourced_statements_from_August_2022" title="Category:Articles with unsourced statements from August 2022">Articles with unsourced statements from August 2022</a></li></ul></div></div> </div> </main> </div> <div class="mw-footer-container"> <footer id="footer" class="mw-footer" > <ul id="footer-info"> <li id="footer-info-lastmod"> This page was last edited on 24 March 2025, at 18:24<span class="anonymous-show"> (UTC)</span>.</li> <li id="footer-info-copyright">Text is available under the <a href="/wiki/Wikipedia:Text_of_the_Creative_Commons_Attribution-ShareAlike_4.0_International_License" title="Wikipedia:Text of the Creative Commons Attribution-ShareAlike 4.0 International License">Creative Commons Attribution-ShareAlike 4.0 License</a>; additional terms may apply. By using this site, you agree to the <a href="https://foundation.wikimedia.org/wiki/Special:MyLanguage/Policy:Terms_of_Use" class="extiw" title="foundation:Special:MyLanguage/Policy:Terms of Use">Terms of Use</a> and <a href="https://foundation.wikimedia.org/wiki/Special:MyLanguage/Policy:Privacy_policy" class="extiw" title="foundation:Special:MyLanguage/Policy:Privacy policy">Privacy Policy</a>. Wikipedia® is a registered trademark of the <a rel="nofollow" class="external text" href="https://wikimediafoundation.org/">Wikimedia Foundation, Inc.</a>, a non-profit organization.</li> </ul> <ul id="footer-places"> <li id="footer-places-privacy"><a href="https://foundation.wikimedia.org/wiki/Special:MyLanguage/Policy:Privacy_policy">Privacy policy</a></li> <li id="footer-places-about"><a href="/wiki/Wikipedia:About">About Wikipedia</a></li> <li id="footer-places-disclaimers"><a href="/wiki/Wikipedia:General_disclaimer">Disclaimers</a></li> <li id="footer-places-contact"><a href="//en.wikipedia.org/wiki/Wikipedia:Contact_us">Contact Wikipedia</a></li> <li id="footer-places-wm-codeofconduct"><a href="https://foundation.wikimedia.org/wiki/Special:MyLanguage/Policy:Universal_Code_of_Conduct">Code of Conduct</a></li> <li id="footer-places-developers"><a href="https://developer.wikimedia.org">Developers</a></li> <li id="footer-places-statslink"><a href="https://stats.wikimedia.org/#/en.wikipedia.org">Statistics</a></li> <li id="footer-places-cookiestatement"><a href="https://foundation.wikimedia.org/wiki/Special:MyLanguage/Policy:Cookie_statement">Cookie statement</a></li> <li id="footer-places-mobileview"><a href="//en.m.wikipedia.org/w/index.php?title=Altruism_(biology)&mobileaction=toggle_view_mobile" class="noprint stopMobileRedirectToggle">Mobile view</a></li> </ul> <ul id="footer-icons" class="noprint"> <li id="footer-copyrightico"><a href="https://www.wikimedia.org/" class="cdx-button cdx-button--fake-button cdx-button--size-large cdx-button--fake-button--enabled"><picture><source media="(min-width: 500px)" srcset="/static/images/footer/wikimedia-button.svg" width="84" height="29"><img src="/static/images/footer/wikimedia.svg" width="25" height="25" alt="Wikimedia Foundation" lang="en" loading="lazy"></picture></a></li> <li id="footer-poweredbyico"><a href="https://www.mediawiki.org/" class="cdx-button cdx-button--fake-button cdx-button--size-large cdx-button--fake-button--enabled"><picture><source media="(min-width: 500px)" srcset="/w/resources/assets/poweredby_mediawiki.svg" width="88" height="31"><img src="/w/resources/assets/mediawiki_compact.svg" alt="Powered by MediaWiki" lang="en" width="25" height="25" loading="lazy"></picture></a></li> </ul> </footer> </div> </div> </div> <div class="vector-header-container vector-sticky-header-container"> <div id="vector-sticky-header" class="vector-sticky-header"> <div class="vector-sticky-header-start"> <div class="vector-sticky-header-icon-start vector-button-flush-left vector-button-flush-right" aria-hidden="true"> <button class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-sticky-header-search-toggle" tabindex="-1" data-event-name="ui.vector-sticky-search-form.icon"><span class="vector-icon mw-ui-icon-search mw-ui-icon-wikimedia-search"></span> <span>Search</span> </button> </div> <div role="search" class="vector-search-box-vue vector-search-box-show-thumbnail vector-search-box"> <div class="vector-typeahead-search-container"> <div class="cdx-typeahead-search cdx-typeahead-search--show-thumbnail"> <form action="/w/index.php" id="vector-sticky-search-form" class="cdx-search-input cdx-search-input--has-end-button"> <div class="cdx-search-input__input-wrapper" data-search-loc="header-moved"> <div class="cdx-text-input cdx-text-input--has-start-icon"> <input class="cdx-text-input__input" type="search" name="search" placeholder="Search Wikipedia"> <span class="cdx-text-input__icon cdx-text-input__start-icon"></span> </div> <input type="hidden" name="title" value="Special:Search"> </div> <button class="cdx-button cdx-search-input__end-button">Search</button> </form> </div> </div> </div> <div class="vector-sticky-header-context-bar"> <nav aria-label="Contents" class="vector-toc-landmark"> <div id="vector-sticky-header-toc" class="vector-dropdown mw-portlet mw-portlet-sticky-header-toc vector-sticky-header-toc vector-button-flush-left" > <input type="checkbox" id="vector-sticky-header-toc-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-sticky-header-toc" class="vector-dropdown-checkbox " aria-label="Toggle the table of contents" > <label id="vector-sticky-header-toc-label" for="vector-sticky-header-toc-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-listBullet mw-ui-icon-wikimedia-listBullet"></span> <span class="vector-dropdown-label-text">Toggle the table of contents</span> </label> <div class="vector-dropdown-content"> <div id="vector-sticky-header-toc-unpinned-container" class="vector-unpinned-container"> </div> </div> </div> </nav> <div class="vector-sticky-header-context-bar-primary" aria-hidden="true" ><span class="mw-page-title-main">Altruism (biology)</span></div> </div> </div> <div class="vector-sticky-header-end" aria-hidden="true"> <div class="vector-sticky-header-icons"> <a href="#" class="cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only" id="ca-talk-sticky-header" tabindex="-1" data-event-name="talk-sticky-header"><span class="vector-icon mw-ui-icon-speechBubbles mw-ui-icon-wikimedia-speechBubbles"></span> <span></span> </a> <a href="#" class="cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only" id="ca-subject-sticky-header" tabindex="-1" data-event-name="subject-sticky-header"><span class="vector-icon mw-ui-icon-article mw-ui-icon-wikimedia-article"></span> <span></span> </a> <a href="#" class="cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only" id="ca-history-sticky-header" tabindex="-1" data-event-name="history-sticky-header"><span class="vector-icon mw-ui-icon-wikimedia-history mw-ui-icon-wikimedia-wikimedia-history"></span> <span></span> </a> <a href="#" class="cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only mw-watchlink" id="ca-watchstar-sticky-header" tabindex="-1" data-event-name="watch-sticky-header"><span class="vector-icon mw-ui-icon-wikimedia-star mw-ui-icon-wikimedia-wikimedia-star"></span> <span></span> </a> <a href="#" class="cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only" id="ca-edit-sticky-header" tabindex="-1" data-event-name="wikitext-edit-sticky-header"><span class="vector-icon mw-ui-icon-wikimedia-wikiText mw-ui-icon-wikimedia-wikimedia-wikiText"></span> <span></span> </a> <a href="#" class="cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only" id="ca-ve-edit-sticky-header" tabindex="-1" data-event-name="ve-edit-sticky-header"><span class="vector-icon mw-ui-icon-wikimedia-edit mw-ui-icon-wikimedia-wikimedia-edit"></span> <span></span> </a> <a href="#" class="cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only" id="ca-viewsource-sticky-header" tabindex="-1" data-event-name="ve-edit-protected-sticky-header"><span class="vector-icon mw-ui-icon-wikimedia-editLock mw-ui-icon-wikimedia-wikimedia-editLock"></span> <span></span> </a> </div> <div class="vector-sticky-header-buttons"> <button class="cdx-button cdx-button--weight-quiet mw-interlanguage-selector" id="p-lang-btn-sticky-header" tabindex="-1" data-event-name="ui.dropdown-p-lang-btn-sticky-header"><span class="vector-icon mw-ui-icon-wikimedia-language mw-ui-icon-wikimedia-wikimedia-language"></span> <span>10 languages</span> </button> <a href="#" class="cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--action-progressive" id="ca-addsection-sticky-header" tabindex="-1" data-event-name="addsection-sticky-header"><span class="vector-icon mw-ui-icon-speechBubbleAdd-progressive mw-ui-icon-wikimedia-speechBubbleAdd-progressive"></span> <span>Add topic</span> </a> </div> <div class="vector-sticky-header-icon-end"> <div class="vector-user-links"> </div> </div> </div> </div> </div> <div class="mw-portlet mw-portlet-dock-bottom emptyPortlet" id="p-dock-bottom"> <ul> </ul> </div> <script>(RLQ=window.RLQ||[]).push(function(){mw.config.set({"wgHostname":"mw-web.codfw.main-5c6f46dcf-vvcsn","wgBackendResponseTime":195,"wgPageParseReport":{"limitreport":{"cputime":"0.878","walltime":"1.359","ppvisitednodes":{"value":5060,"limit":1000000},"postexpandincludesize":{"value":267021,"limit":2097152},"templateargumentsize":{"value":2402,"limit":2097152},"expansiondepth":{"value":16,"limit":100},"expensivefunctioncount":{"value":4,"limit":500},"unstrip-depth":{"value":1,"limit":20},"unstrip-size":{"value":319609,"limit":5000000},"entityaccesscount":{"value":1,"limit":400},"timingprofile":["100.00% 810.332 1 -total"," 56.09% 454.476 2 Template:Reflist"," 23.16% 187.634 41 Template:Cite_journal"," 18.91% 153.208 23 Template:Cite_book"," 13.01% 105.414 5 Template:Navbox"," 10.91% 88.428 1 Template:Evolution"," 8.08% 65.515 1 Template:Short_description"," 5.02% 40.652 2 Template:Pagetype"," 4.59% 37.225 1 Template:Clarify"," 4.29% 34.775 1 Template:Fix-span"]},"scribunto":{"limitreport-timeusage":{"value":"0.487","limit":"10.000"},"limitreport-memusage":{"value":6605605,"limit":52428800}},"cachereport":{"origin":"mw-web.codfw.main-6bb5cf9976-lfdfl","timestamp":"20250327095559","ttl":2592000,"transientcontent":false}}});});</script> <script type="application/ld+json">{"@context":"https:\/\/schema.org","@type":"Article","name":"Altruism (biology)","url":"https:\/\/en.wikipedia.org\/wiki\/Altruism_(biology)","sameAs":"http:\/\/www.wikidata.org\/entity\/Q2559380","mainEntity":"http:\/\/www.wikidata.org\/entity\/Q2559380","author":{"@type":"Organization","name":"Contributors to Wikimedia projects"},"publisher":{"@type":"Organization","name":"Wikimedia Foundation, Inc.","logo":{"@type":"ImageObject","url":"https:\/\/www.wikimedia.org\/static\/images\/wmf-hor-googpub.png"}},"datePublished":"2005-06-10T19:48:57Z","dateModified":"2025-03-24T18:24:07Z","image":"https:\/\/upload.wikimedia.org\/wikipedia\/commons\/b\/b5\/Grooming_monkeys.jpg","headline":"behaviour by an individual that increases the fitness of another individual while decreasing the fitness of the actor"}</script> </body> </html>