CINXE.COM

<!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: '9139e39cdea8fdf8',cH: 'hthRsVX0jxgh5cram6zcQFaTYhCFLA8KTKs2KqAJD9Y-1739838422-1.2.1.1-1qWoTPnyPiDL3PbQZz8O7iReSR_MA4C8fvNfc9nSu9qJSMi_UBcxuLTGXYrIJBCh',cUPMDTk: "\/doi\/full\/10.1073\/pnas.1715640115?__cf_chl_tk=UaROicrgkL_9iGTSFNsbRXXQC4duVzl.QlkdtKIALrg-1739838422-1.0.1.1-cdiXP0T0_QMCgaWQeXMO0_J8HbctPkd55LDhLqZHKqE",cFPWv: 'g',cITimeS: '1739838422',cTTimeMs: '1000',cMTimeMs: '390000',cTplC: 0,cTplV: 5,cTplB: 'cf',cK: "",fa: "\/doi\/full\/10.1073\/pnas.1715640115?__cf_chl_f_tk=UaROicrgkL_9iGTSFNsbRXXQC4duVzl.QlkdtKIALrg-1739838422-1.0.1.1-cdiXP0T0_QMCgaWQeXMO0_J8HbctPkd55LDhLqZHKqE",md: "7oUyhWV7QkmbxXazwbC29DoLM879oMyCKdtyXV.uKfg-1739838422-1.2.1.1-.Nz8MIZ7K_hdH14PTUme6zLojUPGSZzQdDDTTPp9S0jZO_hZ3XrpQy24UjkI5HjExpHNtbtoHrjCLdnKS7n_h8dCPzrFsfZQaITbhchddEX4I3LAknPiLtpv5W_HEdQLN12f5DYNI6Mwl0RBQHoi_g3X.J_MWkzb48Z0B9AiN15DXoRBi8ulNakvo6.BuV_TVq190nGXKdHUv8dn9XS.c6QkRVE_d3sHf.LYyF5uINDLjTiJxQuP5GrmOphzKKuMbKvfT569ONJLVC1njz.PFkf_szM0roJpMx6R4NNoH6_p2rDqtE2USWFZevUwW5LyGOh38patDK5JhP3tFsfDP_tfuT6yM0AVehSfhHf7kwZzVHT0Tzye98_EZ4vK0VBgj1.GhxHCj4RI.G.OXnY7kMfkECJiEDsvyCEyxa8qgDfUuoGO3TAYalUBXSWtfAFv6x6opMurnZ9Q0JYIQvnBnVUyXe749dgOxiTvhNMXGVoXTUrj6MoEadanrD3GpmbiLI.3zNzEtcgotOOZ9oF6SzA2bZ_4kvKouLoxUbTQp48mEAV2WuHvHBfPM0gi9U922GMUdgtWEv8K4OWew5jio.L750noOYRWJax6K9xaGGsp49ReESTm2F4WJfEzQiqcHf2D60E1SongkbVC4V2KAEYUHtTCBsSwahwtxazxqYRztK6maV.ZuL_.CN0By8kme01Tfo9ldMX3pyRVCa8ys2rtpp9X7DsIfiov2QQLyVQ426eN4idGF_XrtBUOvzfAYQ4gXl5Q18Opw0J7_dMBpVjeWXso17OA0UTmF4OUMqjZHvBZSLCWcwE2ENZYnmsi0gyNAMGZ0GRrdzZxPmzor0zFA_5kPsnUN4L3iKUNX7tSeRXbGwPGpqkEutAoxtQYgHOeTGGi8ZytaV3ndOUsSGqYh0CWvXKrbyp5C5Cj81ZVbLy6v7YZxNgn1wkw6h8XNo2zhx0W7MpgXyfAgEEc531xS3ct797UTQ2G.q_UiLmYkU4ZZJSvUEm3B9rOpwjtGWt_guI5E1czOkjnNVPdNLDX_p6RcwdJ5mR_775HCBPV_VlLft0IqqoeXZBLu_GBPIvsgHTBmZfQXRzn_3OreO3PagH0.hYKPJhX9A5uSvMX3a.l5QQBn2FiUr1A978BZAhfIA23sWx.81x2APDcxpFJZaU.FzwS5wSmDB02InbjXH_R3s9K.jqgjUjqD9S6z0fIsSshh7RNqornuSF8znv88YKgNWbjEnI978IsWIJs1F3x5.2khkNU8hrjr1nX5vQeurK5.2D4Kczi0oPh4QjNs2Rz7mclpwPrBjbvvx6uus.2JABVcVvD5DMVESPIdACgSKSxx2sM8Evw.CVAwpvI9xdRxzVwtYLqBGmsLK5OZ_b8fA_UbRc3tVZbPSru2mLngrWCRhgC4u4C73CXND5SmTTlY.9gIwOrz57rv2avPoiIswYgcHmNEf.6RIRqtPTF9pr4f32ta0gRxfXODE7N9xgdDlrvSrXRCFkC7FiRHDjQXqiQdbHqgIR6dBguiSyYDoG4XpVH1Y_HWk_FRIh.yoyxOcJbCPPMYUPSBVNzW2XufB1WjV1UvNd3Fzxmo66yiUt7wZ86_bp7OjWSIcV3bT2CA9S5ESxBbyaCFCBuoG4UzdRyjOQbJD8rcB89.990PMxIYNbJnU6d6.P9h0NZeCfYkxrdpmZ7SJ.cL5Madhot9iFko_mCCG.RUq3q6ZIxWUQVjFg_YNF_SG2ylz75ovFG_95O3oIPxcwlaIthNDpZ_RLRgGK0TtsVYP4zu6nC1s.c3Qrh32sxm41FBEzSwxlVUIVIc12KuabR0gVPCpMYwgOkDIyBz4QJxn9EACh7UlCf17VuBvrM0E7VxZuohuUwdH9fppNmPu21x_MxJqxEz_HDZhaUjLe6qzDUwZ3mN2PFo1_0z0_EBAA6PCCUGzO7Z5bapTzdgY2URGTO3D21XhgFncrmGdwEdhuhCcGT.VvpJT6vWl3JV.qvl20uoqOTxOJxVCPHmhw3HT9R_vUTTT488wMo7p4LvfuxZMbRiNiuSrUAVY_cP54HHAI6MsGtHzGc28sFe2QdCCAueVV.3qXftDQBLbWprUDvbO9dpx2LbeAeHh6LQkHfZvK9jamvoIkKLscinZ37ol7yS7JPFLjJDiszIFdMfK.qS66Hgr7Ve2lo8iasiq_kOqxlcNRM2gK6mLlZaPQlP4zIv7Zz2wp7fQcGY4U3FZeUFpY6aATZoWhhFbnlut8W55S8Jly8j_Aeir12MMmoNIC6rq_Y_HiAIV_UnhOyLq4lLDZbNZ8RQpn7e.IKu_vM8h63dSksMCUrOu7Q1Eil.vOc7g42VdDmXZctz89EeL6cw8p4.voSyJroeo5Ea9XIbgX9ul3b.ITqdgiLT5MuUg0vkKafo_nhgQXi1rbyTelhPPwis3EzMrcrCWhP26xPtJj8gbpx_WYCKDpWQkGVLSlDCuJKDKmGU138ubcykvD9JBVfEpi7qUYfulFUXI.rjtacqbDDL9JUAFAxgxmlEuluOSik_RARkrvUkgkdYQjqo0QIU_pYBzxzEVz7gofvbj4MjFO2SPQyZoutZLFM6aQ",mdrd: "IJqvVz2TX9r_.OPQKDhHxB4LyL4gzD6EcYRrJnJCfTc-1739838422-1.2.1.1-63GfRMUwwd4vn0PU2xzuYp4rwIvsFC8C8vWBLtaItBLEPX9S_FokWIVWHOQhd7UCTu3MX9vVRy6RllTBgA5MyUWc4dWAiJK7h9srjxO84KQN3wU6Y8WEJ9aXu4xR.fT7fbRUmtchwOIFHxbYDo1OftQtmFMFshGMRWmCv0MwMAnbIUNxtA0wjEsMlf5XunzdOPZwEt9zwIoR2WKpoKoCnT61YLa9CPX1ZXKD2YpMXCLkkvHWYLboysCNJ.Aelo7RZgTBokzJ6wWlv5IFDKVbw_EtmmSzLMfOmDibyyl7nQqw0TmiUiwj3O9LJFqvRKwiORoImvFZ7Ufckl2fAiU62HJdyhZSbDOpO2JWj2wnyfe4rNTFhiRENUBH0TNefKsi0Q6b9qBlRWscv8qVsbtjlk_3uZYc075WY9HcqQAu.mGcuN3c8IKtDl96I8Y_BIpkvbeIDPLOMbn2xiVGsG63Rg5kSAQnA2wWCTzJw_2RYQGefM2FetP7SXgv3fLTJH8wFo3rX74F6nI0XRuyI7e7wLcXTysRczN1mi_Qlvc8cfDRyEW9dgHhLpXpk3DzLLABgl4GWPmkK0yMH7nx6K.zKKUWlEuskRGTH1FX6u4haYC5NqAl8lv2FP3ahgok.DUWCSYiw_fgFzt3whnhdFGdlO7po5gBqflyK6Ffj6p17yQZtfpokrc_C9KMBmwMVpVZa7tgkA8JfU20INkXh6lmmHzZYvjXljW03gFzb7pdV0s.71fEc3keiFCyt3UzW.1.IcY3YgGzyYMVKYGTwXThK_VtpQgKJRq02gXunwk.RneSuI944ORAJOse7G.nZuMzTmiBFBKQK2MGFTKmlBT3LIqHPVVhngpVGTQwo1Z1Pj6D7bp0ORgZZvKtR_B0efjGGDGpXBlMDMrdA56JfrtF5vKcgKjmcl_Sr2XgGnV_p45EbecapCRBEnvaCK15SyiNN.bZPCG384mlFIugbYiJJQ0Bai_q3lIgEZ7FA6x4lYtRQO_G1jX.ljyR1EFsEoSiCacu.Fosr90XsdtOUhONRWCxnOy8.cM1BY0P7nkC4bwsis1u_HwR.IXrJlmwBFHO27BBYphpbD1DWGLA1Wlmn3Qug8FpcUABJENCMvCZjZto.GcEbM.ln_8A0.1Xfs3mAcUyZ1RJSoeowUUhxnQ5Mi26uHp1LJWjfcNEtShW.z0tNbOUkWoVf73UFndadpR1NzySl3ZTlwAKVT1V4rGPBD1DIzJ0b2ogMNZTq5pDVH5vAelUr9Hkvl7depBpmUrm8Jqwyij.em9RiN99BqHlxbbCE7xZtFuFnljK5gPaWihgP65lP8iPKPty27t__z8Z1JVWkp5baLSzPdMSaYUphgfU4KO.UkOh4KLqUEGAPWZS3o1lLP7SuToTjE0xsWcp1132sLMXWubdwKa8iPm51utT2V6gNCywHuaiwDVSRUhI4oElL0gvWwYJPfY1TWqPgfviqt9t0AqBam3fD9mwjK90mifpPZOSsibArio7mXMRqSZX9K1D5DDcrhk5l._88ZF.nQ_T9yipqZGgV7vtJAZeCCZhcYG8.QSLnVB2yFhGIx4yYTYPLHjMIhaNWVSNnBfwdieCx4vpMI9jjPqfPN.eiuO5kccLTdk7gQOrT.hzTIS4saB61OBx1ZsLNmSF62XfUCFFCFwyEU1MIO3begazb_1.P4BhCvdez5Ee5dWbis3RKSbiJqG_9Gi5DDeI8bykUhBoDcPFNv.Ftk.oT4uZgjWSgnElJq6PKwCTS952H47kZAmfNP6ECp.ZRCKo.m17Wi3xJJ5wNSHcS7NNJWL_n3BrNWqw6nd._02xppdD0kE42taXehM4QT8N1YKgVl2kNeNhyPGaXNlQkbB3q0Dp7npQU3oYUc9dC53cE_dwthrAmsiAEkxLDSSwMPLjXHWjeUPMA4SY0m293psJkA"};var cpo = document.createElement('script');cpo.src = '/cdn-cgi/challenge-platform/h/g/orchestrate/chl_page/v1?ray=9139e39cdea8fdf8';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.1715640115?__cf_chl_rt_tk=UaROicrgkL_9iGTSFNsbRXXQC4duVzl.QlkdtKIALrg-1739838422-1.0.1.1-cdiXP0T0_QMCgaWQeXMO0_J8HbctPkd55LDhLqZHKqE" + window._cf_chl_opt.cOgUHash);cpo.onload = function() {history.replaceState(null, null, ogU);}}document.getElementsByTagName('head')[0].appendChild(cpo);}());</script></body></html>