CINXE.COM

Just a moment...

<!DOCTYPE html><html lang="en-US"><head><title>Just a moment...</title><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><meta http-equiv="X-UA-Compatible" content="IE=Edge"><meta name="robots" content="noindex,nofollow"><meta name="viewport" content="width=device-width,initial-scale=1"><style>*{box-sizing:border-box;margin:0;padding:0}html{line-height:1.15;-webkit-text-size-adjust:100%;color:#313131;font-family:system-ui,-apple-system,BlinkMacSystemFont,Segoe UI,Roboto,Helvetica Neue,Arial,Noto Sans,sans-serif,Apple Color Emoji,Segoe UI Emoji,Segoe UI Symbol,Noto Color Emoji}body{display:flex;flex-direction:column;height:100vh;min-height:100vh}.main-content{margin:8rem auto;max-width:60rem;padding-left:1.5rem}@media (width <= 720px){.main-content{margin-top:4rem}}.h2{font-size:1.5rem;font-weight:500;line-height:2.25rem}@media (width <= 720px){.h2{font-size:1.25rem;line-height:1.5rem}}#challenge-error-text{background-image:url(data:image/svg+xml;base64,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);background-repeat:no-repeat;background-size:contain;padding-left:34px}@media (prefers-color-scheme:dark){body{background-color:#222;color:#d9d9d9}}</style><meta http-equiv="refresh" content="390"></head><body class="no-js"><div class="main-wrapper" role="main"><div class="main-content"><noscript><div class="h2"><span id="challenge-error-text">Enable JavaScript and cookies to continue</span></div></noscript></div></div><script>(function(){window._cf_chl_opt={cvId: '3',cZone: "pnas.org",cType: 'managed',cRay: '8e798e61bd38eba2',cH: 'x9M0h.9eu0FfI_v7BhrVHlPMqAYh.GvmpXQozP22Ifk-1732452956-1.2.1.1-8Rfywte2JGpGt1DHYLZoLbVFu8uelL5VlQErPUh3pKDoCf2bNS_AIuODwrYCl3Te',cUPMDTk: "\/doi\/full\/10.1073\/pnas.1005780107?__cf_chl_tk=.Y6EA_7m2sMsxPh7LME1AUc6baCQVeFOv6VlhD2X.dk-1732452956-1.0.1.1-zQGSglz46cfzrS7gi615W7IwFvyn.yv4U8L_xCXvAOs",cFPWv: 'g',cITimeS: '1732452956',cTTimeMs: '1000',cMTimeMs: '390000',cTplC: 0,cTplV: 5,cTplB: 'cf',cK: "",fa: "\/doi\/full\/10.1073\/pnas.1005780107?__cf_chl_f_tk=.Y6EA_7m2sMsxPh7LME1AUc6baCQVeFOv6VlhD2X.dk-1732452956-1.0.1.1-zQGSglz46cfzrS7gi615W7IwFvyn.yv4U8L_xCXvAOs",md: "FoRqncIXRF1oQnyu84Vfz775rabqyva7e6oybXXJAQs-1732452956-1.2.1.1-rIZxjDRKiTK2ZCD.09HDvVAeWpPg.XsCehhS1vsa94x6Qu9weNZIre4biD_uYYWPkGAq5y9w6Vj9ciNDC7l7ku6Il_jyFntB_A_PSWzuviFpsQOYlWDPtNUb8WligYynLFENOORaj5RprZqa.h_psAXqOyQ6qUbNB3UTcqlrt1lB3kMpqslgi2O6Le22tZjOhWKFT5KwnF_7UUqHVyqU3nK0liedfrSLU1bYulxG_xUFSJs5H64o9r.v5ooGfV23IqTHKZtcLwJc7GM3HqxAZQO2aK0M8DC3Vyy6lY.2Um76Tl0DeHH5ySJSJMtHJpwnWcEsuzg0Ua3qISX.cAO4eJSz9j6uxqVazQX4pmonroEka_ckmOKD1IWKdJn97YCp7HmhFfBCTR_PooEh5D5wm2eR8db8wtrd2D0eKqvQaynYoiRjReLV54vnWUdlA2OmZ9cIdVdKcX1OLZ86cvVq4M4WvnwV_poxWP5kaTbEPZxAnHPhrwufcms6j9BapEULGVAe5eNhrExW1MgQPjGqb8wPdl1VwBSXhU_avWK0UYDZIE_Q25IpdPIATSQ4mKJOHZPeo3V5yAdZ.ygKCZrWaBPUWbVIFBHfSzoxZT02Fq6d20SXsd34xM2kgTAxD2VhG5I0Gm9.vfWyRgkUZeDZpMHXe6os.yqHl7kbWv8mht9uyT0SBGMfrhHmCvcm.CXVWFDefB5T9AQ3p04KWS2gWr6VmZQROPR_OEjniv0N0aqLaLBh01XunB2qlx64y4PFV8Wh6LwYIRDQxbBgVO8OBK9TexTpMNmlnPfmw2AxjCIjmgdYZ.9_9ZwxJ.hbsCjqqPXr9Vr.K6DCeqqa_N2QmVZw0MNWlD8c1uJdvWnh.pG9L9lUpikS_w107NlMrKy1ljyWdWF4TIR3HcSsxyMWLFZ7IQaa7W8tW9ZEGKI2aASzxbKejp4UJ8yrwZc4CrSHgMXSAL6dJzfQ7xoi0woSwxcsG0TifsXw_6jHrcHNGPYiRhP.I2wm9y0BLtvwyBcCK3uJeJrkQONr_GNud0xraLGOSriusy83uVnWpAevN5osctq_wZreU8Xa_9jd3bRPizhXmQE6xvfXQ5_vTiLOhDsxangPBARYMPscqFKbsZEJp5mK5gxmVE9OeI0R4UFdYuYVcx4tgb2RVVcBA1vzHmvC.XTfr30lsjvyxMkKbY2rC4ZMl4.YCzuT9aq0cJNtgJKFgc7Bc2uAARcHoVq2M4PaLlyeDghF2voQ0XA2mJGnnhHw9WqQBDKPe8QWaczJ5fxyFcQcw7j4aQylf3P8J0GqemyyTEdFy6sRzdr4ezxMsuYM_KLol7yw9qrtT4sQwq2sXGTxuADK0dt2nA.IVPVbChRfE4uZ7DGYljNvOhOsWh.1Vk0DQCgHkFHYOPNnbLWHdi5RL..yH5rAHphntRq7_7ZKn3prp_yhsBgL61ea5UfNGkn4QRuXzaQeklldv.Fkeg4DRaAVn37OgrYkWK4Qfpo8JvAQIyGFoIRksx0egv0okKIH305yfAaVhmxqnbPdhrLoRdH8zIoVlnJJjlhz6wscDNcgNl15frO32VG3OHuNxSDx85eaYOh6trJJL6.uZ9c_zRwnoq2ec7yaM78HEixj1ZPBc5kyFTJyafZkQOMXcpUbOJTRtahHNQQ7_KhhLVcIXn7y2Vz.KJybLQ5ZgPWF51kOrMPlW4N_mrQ_Nm9kSs.W37kN8gdYUdtiD5lMx6ey21DP2qDWu81MBxy9T45_lZAyOq9LMwA9Sj7ikLA.cw3yQpJBJGoduc98YH15HkvEud_ZZlwRCQstoq0Srvs1wI6C94sePoHc.WLWQOlBnxbxihVzi0SP40dhtWFCWvz5_jvfet1Z.f_oWTxKWkWcVmjhtRoSaauFNaLEHBPPE7b1WByF8oXOie3M0XYB4_STEHyIxNVu951UXrqUMzY1wBe6IRAcDADUtcYipLxJ29qMp3lBmrziKwc2V9laN.b195Roh094AhW9JqjPl4TglmhenmzF9gb1A56M5f3LsBeLhRH0UYHvWakKy4lCC9bnxN86cvqQm98FF6F4_ieqsn_zqXUIjSiurC75xZn1.g1W2KZvB9as1Vvveuicl0zfG7M5_RppnYJR6qpE0MMdXKPgES4FpJGcDV7waE4eMEbFZbO9GQgowo9uqilagesemdlmfJ42gRPvakt6ATBj1jtneLD6YdQkkQKju5BVQU77AwjhCB2C1bVg65cq4E50P4UxKaH.L._WVdXzrrF_mD0DZ2Hdt44BuHqcAkPmpQqBOWwxDEnEnlK3V_.Req3WjIgxId1zp_3o7G0Jo48_zlAlBPSk1h3BwIC8zUSmhVaIqovAxzjj1dbYbEn7IKVJElRmm0M.Ta4i2mm7L5f30u4bqzsT6m9qvxMSgD9DL0dJFAhX.l0AiGhxb4gvdVuUIxyZIyiNWCHpFF9JyvFR9jEqWBvKih6l0gtBLywy9MHlhMeK8A7EyOA38xkwOlqjAtSsAL5hT4NbqVtvL_cW_xYjw8bNyrX8KUKSIt7pyp9LrdmllBR62tbKp9bMsT_XNJcvUOVA0IXfFbp1WA1_8APp53I9z4lMvvWJsHIxVsvOSWzmwdqJVmhZ4wbkZfJnddEVWi7vFUOAwEbwp0dX4JSVH0hZztfDMs6tWmPhve6jweXfE9b4GDdCzawUbci5sZUJ4Z3bbiGw5N0QyzJMUqM_gAfW2uQhRMkEG7NXCWPWE4DjCL_RPVYU_643EgbYsBVt5JlfVX1WFrvfbJKYT3f.cdRhId_oU5q.c5afxZK_zm6x3kFwZeO91iGHBjkPAsehd8eYQWnC4h8BiWpNKMqMyKjJf3pXYHzTQoj_m1IZK03PpyiOodi6BDCD2pJj1ZL_oQ63AKeUX_8FdzLNYiFK4AJ8SoMTRXayyz8SrutLLH21tU7JEmU2at43KeAEHjurxWCWZsy3SE64eVcaocNLVAgn6SOZ9QE",mdrd: "joLNjPjcIdA29_8g5NosHoFqhIW_f6lmmZ9vmVfFVXI-1732452956-1.2.1.1-2_p5Qv2Dfb5.9LTDzUXlvovegipEUuzYun15K_FOlaL6M6KBpeevWB7a.aPCD7VuiPmQmdvFHyeHntao62M10nxqHxFCDl8jZgYU3PqbcEHOUX8.lI66IMY0bv1ZQ7_P3p.BCSEIJBT1XVXZ5gpICoUevkrDkhFZ_x._mEw7M.Mn7DzRpQO7omPAUzXLJEBFvJrIGpyVLZXy0tl.rLGYkDCMkqOFOuPJzjt6iXWzd0xhT8imjjpFPecNSHJocx7h2hL95o5MzWpFsPzbUz8vFC18mUDUi._pRZVfX3EwR0aZZCEPo_qXlXic4IGEDr6c3g_5oAMlXoEfG8mrNFdAI1TBY2reoRk2e_M4PctJtUsUCiIBIZjDExFRjb..g7bRMgczZhqDpFhNIN3UuGuvBh4kk441jhxe2nJUSz_CdAcpKyyBrFLy0kBihB9kXCN5R6ELX8opeela4DkIh_Y6Y4diaJ5VOpNmlCIiOxKTTcfqb2lIfxU8g5oAobqsabqQYanIZRvxRDAXuXjoyjbUSyJpF6GsqKKGWxhv_dJOm8L_Kn5ajZMZXfDo8SI78bRgUZXEYcgpRY87X9LLjjK_DVq.UfTXdNlLoclCc7nmHvgBfyLOG3.IN_MvDlDpf4.rKH6f2klbC8Wuu0rtUVczprhUhC_PvjIurKXWIl54SOlbkgscAvGdosDsCHj2Ze9qYllToti.LrJEew9PWWc2NyVRuLNXD8ZKMjw_nm9Q.uV2ullRmKklXXEqSYJAUkPwH0XQ61uwu41FI3IIjW0SdpX86Xy4bk__c78htRRWYtCVfSabZJW.4Yrwbe7YDiaeu1poz14EMcxrVpncCRwfyK.jQ_m.V113SYolkRoEUV5jvZy0upYPEVLjByjtMfEbVFtJ2sCxGMlbNqxEaUYnJu2UltCV1X3U1rOYpOL8p.jZ5hqeLrtXo.5pWmPVVclenVRqqGSX9h9jKE0JnR948DRVR0g5Hi3wnJO3F6uoev7Xj456Q.VfPpUvq3fLtQOaKuhg2fcHhY54J7u_4vIxvShPKecpzgnDdDwCmju2wDWHpyN85tJeDy3ejgd2DZg965PdCYFN1djFwGD_wXQjS4oV3iJVQYFikJLKWDOFeRH8v8veWZE7iVRFectg3CuwzK6ahHsg2XCEwJPeGoa6Z52K6S23gCq3Is4Zx7TGK24.m.ZDasxNGULtAm_jefWzxiSiwi_dWuUtgCCkX2BezymQpZqSAP5rCC_USoHkKo_DefTojLnTkGvcNOmJnF6Qxr69Azsh5fhD5ZgtiEP3ND7prQrUxWioIKUQSdZQnEGHsnymzJD0V9279ZJ0JrBPyRO1y2wSCcUqx9N2RMW4zNPeUY0at3EvGsqTYxaCqT5ygEgTUfqy.SjmCwZ7tJqFUEDspnP39IC1rKbC3rEMUsVc4ATAk_ajmcdlJLzQMGy9Cm3o33vr29uAk.DqaYMYFH1n0o2Ei7DuILEEDWOvDybFhu_jrEXYGn7Hd8pakXB_LJkMAdfPBscKpZkwe_2Lll93ddiPXdAFXCL6Kr_RMDDqVwigASCqZof_lbqkW30960Q4Si0jIJPONGH6MVDh8ERCab6XZVfyoj179A4.Z3Nm60yL36dFJ8tnHvTE4HIpWwqYm6bR6EvGuWexZD1xF6ZlaKaBaEAPgj8YdHcMsWx_Tzw674VWFalN0KJIoTtRHfy8.OTk12Um1EsJezTtwvSUZ2zZGZIY6HSJoaMq_rBllOpbM5dWaCMBsGLcdPfylfxSRZcYyDKEE3rlkTQahe79b429egwo.ytlngO3i1qtd6Z0oZeT8wCkCt8i1G2M0ClYTaRrWGML2GT.2hkCeeXaN7ydQttfCbe0WWQxA1AucOO0HaUe59p9SdgeMctu2rESUYnBuKM1KsWruoPydJ4P1VlN4ZkM.WfuAI5RY7XF1E5DGlqNO3fpCdQUxdS3kQDLGlWE1C_YhviTvKFM"};var cpo = document.createElement('script');cpo.src = '/cdn-cgi/challenge-platform/h/g/orchestrate/chl_page/v1?ray=8e798e61bd38eba2';window._cf_chl_opt.cOgUHash = location.hash === '' && location.href.indexOf('#') !== -1 ? '#' : location.hash;window._cf_chl_opt.cOgUQuery = location.search === '' && location.href.slice(0, location.href.length - window._cf_chl_opt.cOgUHash.length).indexOf('?') !== -1 ? '?' : location.search;if (window.history && window.history.replaceState) {var ogU = location.pathname + window._cf_chl_opt.cOgUQuery + window._cf_chl_opt.cOgUHash;history.replaceState(null, null, "\/doi\/full\/10.1073\/pnas.1005780107?__cf_chl_rt_tk=.Y6EA_7m2sMsxPh7LME1AUc6baCQVeFOv6VlhD2X.dk-1732452956-1.0.1.1-zQGSglz46cfzrS7gi615W7IwFvyn.yv4U8L_xCXvAOs" + window._cf_chl_opt.cOgUHash);cpo.onload = function() {history.replaceState(null, null, ogU);}}document.getElementsByTagName('head')[0].appendChild(cpo);}());</script></body></html>