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Across 15,836 people existing across the span of thousands of years, genetic records preserve repeated rises and falls in specific variants across West Eurasia.<\/p>\n
By tracing those changes over time, Ali Akbari at Harvard Medical School (HMS<\/a>) showed that hundreds of variants steadily gained or lost ground in ways that cannot be explained by migration or chance alone.<\/p>\n Earlier work had pointed to only a few such cases, but this larger record reveals a consistent pattern of change unfolding across millennia.<\/p>\n That pattern poses a deeper question about what pressures made these variants advantageous at different points in human history.<\/p>\n New pressures in settled life<\/p>\n After the spread of farming practices, the pace of directional selection<\/a>, when one gene version keeps gaining ground, rose increasingly rather than fading away.<\/p>\n Denser settlements, new food, and closer contact with animals altered what bodies needed to retain nutrients and fight off infection.<\/p>\n Other ancient DNA work showed strong selection in immune genes<\/a> after farming became normalized, matching the timeline of the new paper.<\/p>\n Adult milk digestion was one familiar example, and Bronze Age data<\/a> showed that it kept rising within the last 3,000 years.<\/p>\n The genetic cost of infection<\/p>\n Several of the strongest indicators were found within genes that were tied to infection, inflammation<\/a>, and the ways bodies recognize invading germs.<\/p>\n One variant linked to celiac disease had a significant increase, even though wheat farming would normally render that result unlikely.<\/p>\n Another changed the balance of A and B blood types, hinting that old germs kept produing different defenses over time.<\/p>\n Those reversals matter because a useful gene in one era could become costly when diets, germs, or living conditions changed.<\/p>\n Limitations of modern labels<\/p>\n More than 60 percent of the selected variants had links to present-day health, behavior, or body measures.<\/p>\n Sets of small changes moved in tandem together, lowering modern DNA-based estimates for body fat and schizophrenia while raising estimates for cognitive performance<\/a>.<\/p>\n Those links do not mean ancient people were evolving toward modern categories like schooling, income, or psychiatric diagnoses.<\/p>\n Modern labels work to interpret current societies, so the selected trait may have been something nearby, broader, or completely unmeasured at the time.<\/p>\n Why the patterns remained hidden<\/p>\n A 2015 ancient DNA scan<\/a> found just twelve strong signals, revealing how much older methods had missed.<\/p>\n Earlier work often struggled to separate selection from migration, population mixing, and random trends in small groups.<\/p>\n \u201cThis single paper doubles the size of the ancient human DNA literature,\u201d said David Reich, professor of genetics at Harvard Medical School.<\/p>\n Better filtering and a much larger record turned a faint signal into a readable pattern, without claiming every change had contributed to survival.<\/p>\n Selection as a fraction<\/p>\n Even so, the study estimated that only about two percent of the shifts in gene frequencies came from selection.<\/p>\n Most movement still reflected migration, mixing, and chance, the everyday reshuffling that happens when populations grow, split, and merge.<\/p>\n Because the genome changed so much overall, that small fraction still touched hundreds of places with clear survival pressure.<\/p>\n That finding helps explain the paradox at the heart of the study: there is weak influence in total, yet many places remain where selection left its mark.<\/p>\n Ancient lessons for modern disease<\/p>\n Ancient DNA can also guide medicine<\/a> because past survival pressures sometimes leave present-day disease tradeoffs in the genome.<\/p>\n Variants favored long ago may now raise risks for immune disorders, metabolic trouble, or other illnesses in modern settings.<\/p>\n \u201cWith these new techniques and large amount of ancient genomic data, we can now watch how selection shaped biology in real time,\u201d said Akbari.<\/p>\n That perspective could help drug developers avoid treating every harmful-looking variant as a simple mistake.<\/p>\n West Eurasia and beyond<\/p>\n Researchers have already posted their data and code, opening the door to similar studies in Africa, Asia, and the Americas.<\/p>\n Future work can test whether the same core traits were favored repeatedly, or whether each region followed its own path.<\/p>\n Scientists may also be able to further explain why animals like cattle or chickens adapted so quickly to human care.<\/p>\n \u201cThis work allows us to assign place and time to forces that shaped us,\u201d said Reich.<\/p>\n Separating evidence from assumption<\/p>\n Modern trait labels can tempt people to overread the findings, especially regarding schooling, income, or intelligence tests<\/a>.<\/p>\n Those terms come from present-day databases, and the selected DNA may have affected older behaviors or bodies in other ways.<\/p>\n Nothing in the results says any population evolved toward worth, rank, or destiny, and the authors stress that clearly.<\/p>\n Careful interpretation matters here because the power of ancient DNA now exceeds the simplicity of many modern trait labels.<\/p>\n Evolution remains in motion<\/p>\n This study makes recent evolution harder to dismiss, because it ties genetic change to concrete moments in farming, infection, and everyday life.<\/p>\n The next advance will come from testing other populations, probing the biology of standout variants, and learning when old advantages turned costly.<\/p>\n The study is published in the journal Nature<\/a>.<\/p>\n \u2014\u2013<\/p>\n Like what you read? Subscribe to our newsletter<\/a> for engaging articles, exclusive content, and the latest updates.<\/p>\n Check us out on EarthSnap<\/a>, a free app brought to you by Eric Ralls<\/a> and Earth.com.<\/p>\n \u2014\u2013<\/p>\n","protected":false},"excerpt":{"rendered":"Natural selection has reshaped hundreds of human genes in the past 10,000 years, far more than scientists had…\n","protected":false},"author":2,"featured_media":399288,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[10],"tags":[163,85,46],"class_list":{"0":"post-399287","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-health","8":"tag-health","9":"tag-il","10":"tag-israel"},"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/posts\/399287","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/comments?post=399287"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/posts\/399287\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/media\/399288"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/media?parent=399287"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/categories?post=399287"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/tags?post=399287"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}