The scale of the study provides an opportunity for researchers to test ideas about how culture, climate, and migration changed disease pressure over time.<\/p>\n Skeletons hold disease secrets<\/p>\n The study was led by evolutionary geneticist Eske Willerslev of the University of Copenhagen<\/a> and the University of Cambridge<\/a>.<\/p>\n \u201cWe\u2019ve long suspected the transition to farming and animal husbandry opened the door to a new era of disease,\u201d Willerslev said. \u201cNow DNA shows us it happened at least 6,500\u202fyears ago.\u201d <\/p>\n His team sifted through more than 400 billion sequencing reads and used chemical damage patterns to confirm which fragments truly came from ancient microbes. <\/p>\n The analysis uncovered infections in roughly three\u2011quarters of the skeletons<\/a>, indicating that illness was a constant companion rather than a rare ordeal. The oldest sample, dating back about 37,000 years, contained mostly oral bacteria still common today. <\/p>\n The results revealed that blood-borne infections didn\u2019t show up until people began settling down, storing grain, and living closely with sheep, goats, and cattle.<\/p>\n Farming sparked new infections<\/p>\n Livestock pens and crowded villages arrived in Eurasia around 8,000 years ago, and the genomic record registers an immediate uptick in disease. <\/p>\n A clear inflection point appears at 6,500\u202fyears ago, the moment when zoonotic pathogens<\/a>, the kind that jump from animals to humans, first show up consistently.<\/p>\n One notorious example is Yersinia pestis<\/a>, the plague bacterium, whose oldest genetic trace dates back to about 5,500 years ago in western Russia. <\/p>\n This pushes the timeline of plague back two millennia and shows the microbe shadowing early farmers long before recorded pandemics.<\/p>\n Waves of new infections<\/p>\n A second surge of infection follows the migration of steppe pastoralist<\/a> groups roughly 5,000\u202fyears ago, when horse\u2011drawn wagons carried people, livestock, and microbes across the continent.<\/p>\n Skeletons from that period revealed plague<\/a>, relapsing\u2011fever spirochetes, and the parasites that cause vivax malaria.<\/p>\n Such waves of infection probably devastated local communities, clearing ecological space for newcomers and turning pathogens into unlikely allies of conquest.<\/p>\n Ancient immune\u2011gene data hint at strong selection beginning in the Bronze Age \u2013 a genetic fingerprint of relentless pressure from emerging pathogens.<\/p>\n Human infections from animals<\/p>\n The catalog reveals that cowpox relatives, leptospirosis bacteria, and meat-borne yersiniosis showed up soon after pigs, sheep, and goats were domesticated. <\/p>\n This finding aligns with estimates that around 60 percent of emerging infections come from animals. Close contact clearly reshaped the disease landscape.<\/p>\n The researchers also found skeletons that harbored two or more bugs at once, and these co-infections can worsen outcomes. An ancient Viking\u2011Age skull carried both hepatitis B and plague DNA, demonstrating how mixed infections may have driven sudden mortality spikes.<\/p>\n Curiously, no clear evidence of tuberculosis surfaced, probably because its bacteria rarely circulate in high numbers in healthy blood. But as the team notes, absence of proof doesn\u2019t mean ancient lungs were safe \u2013 only that some microbes leave fewer traces in the molecular record.<\/p>\n What ancient infections teach doctors<\/p>\n \u201cMutations that were successful in the past are likely to reappear,\u201d said lead author Martin Sikora. She noted that the ancient genomes can help scientists anticipate future mutations.\u00a0<\/p>\n Vaccine makers already test candidate antigens against panels of modern strains \u2013 a practice encouraged by the World Health Organization<\/a> \u2013 and prehistoric DNA provides a deeper benchmark. Comparing lineages over millennia highlights which protein targets stay stable and which drift.<\/p>\n Old plague sequences, for instance, are missing the ymt gene<\/a> that helps modern strains survive in fleas. This points to the key step that turned a local infection into a global pandemic threat. <\/p>\n Similar evolutionary tipping points could lurk in viruses still endemic in bats or rodents. Public\u2011health planners can combine the new database with climate<\/a> and land\u2011use models to gauge spillover risk. <\/p>\n Pathogens rewrote human genes<\/p>\n The skeletal archive captures natural selection in action. It shows that human alleles linked to inflammatory responses became more common after farming took hold. <\/p>\n The same alleles, still common today, now raise the risk of autoimmune disorders in industrialized nations.<\/p>\n Immunologists argue that this trade\u2011off is the cost of survival: genes that helped ancestors fight livestock\u2011borne bugs can misfire in cleaner modern environments. Ancient DNA<\/a> provides the infection history that scientists need to test that idea.<\/p>\n \u201cInfectious diseases have left lasting impressions on human genomes, as selective pressures from pathogens have continuously shaped human genetic variation,\u201d wrote the researchers.<\/p>\n \u201cWhere and when different human pathogens first emerged, how and why they spread, and how they affected human populations are important but largely unresolved questions.\u201d<\/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.\u00a0<\/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":"Using ancient DNA recovered from prehistoric bones and teeth, scientists have built a 37,000\u2011year timeline of human infections,…\n","protected":false},"author":2,"featured_media":264065,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3846],"tags":[267,70,16,15],"class_list":{"0":"post-264064","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-genetics","8":"tag-genetics","9":"tag-science","10":"tag-uk","11":"tag-united-kingdom"},"share_on_mastodon":{"url":"https:\/\/pubeurope.com\/@uk\/114851296289554553","error":""},"_links":{"self":[{"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/posts\/264064","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/comments?post=264064"}],"version-history":[{"count":0,"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/posts\/264064\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/media\/264065"}],"wp:attachment":[{"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/media?parent=264064"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/categories?post=264064"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.europesays.com\/uk\/wp-json\/wp\/v2\/tags?post=264064"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
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