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Along the coasts of Southeast Asia, Sama-Bajau divers still descend more than 200 feet on one breath to gather food from the seafloor.<\/p>\n
Measuring spleens and scanning DNA, researchers at the University of Copenhagen<\/a> found that many families carried unusually large spleens.<\/p>\n Because even non-divers showed the same enlargement, daily practice alone could not account for the difference.<\/p>\n That result pointed to inherited change, and it made the next question impossible to ignore.<\/p>\n The spleen reserve <\/p>\n A large spleen<\/a> matters because a dive triggers it to contract and push extra red blood cells into circulation.<\/p>\n That burst buys time when no fresh air is coming in, because more cells can carry more oxygen.<\/p>\n Herman Pontzer, an evolutionary anthropologist at Duke University, used the Bajau routine to show how extreme that workload became.<\/p>\n \u201cThey could spend 4 or 5 hours per day underwater,\u201d wrote Pontzer, describing a routine built around repeated breath-hold foraging.<\/p>\n Speech at a cost<\/p>\n Human speech also depends on a risky throat arrangement where breathing and swallowing compete for the same narrow space.<\/p>\n During a swallow, the larynx, voice box, and nearby tissues try to seal the airway before food slips downward.<\/p>\n Even with that protection, National Safety Council<\/a> figures show that choking killed 5,553 people in the United States in 2022.<\/p>\n For Pontzer, that hazard is part of the same evolutionary bargain that made flexible speech possible.<\/p>\n Mountains demand oxygen<\/p>\n High mountains create the opposite problem, because every breath carries less oxygen than the body wants.<\/p>\n In response, the kidneys release erythropoietin, a hormone that spurs new red blood cells, and the marrow starts making more.<\/p>\n More cells can steady oxygen delivery for a while, but they also make blood thicker and harder to move.<\/p>\n That trade-off helps short-term visitors survive, yet it does not explain why longtime highlanders vary so much.<\/p>\n Two highland paths<\/p>\n Across the Andes<\/a>, many native highlanders develop larger lungs and rib cages while living with elevated red blood cell counts. Growing up in thin air expands the chest and improves oxygen transfer for many residents.<\/p>\n Far away in the Himalayas, native communities solved the same shortage with a different balance of blood, breathing, and vessels.<\/p>\n Independent histories produced separate answers, showing that one environmental challenge does not force one biological solution.<\/p>\n Ancient DNA in modern humans<\/p>\n One Himalayan answer centers on EPAS1, a gene that helps regulate red blood cell production<\/a> at altitude.<\/p>\n Rather than driving blood counts ever higher, that version keeps them relatively low and reduces the risk of sickness.<\/p>\n Genetic evidence showed that Tibetans likely inherited the useful stretch from Denisovan-related people after ancient interbreeding in Asia.<\/p>\n A chance encounter tens of thousands of years ago later became a survival advantage on the Tibetan Plateau.<\/p>\n When blood thickens<\/p>\n In the Andes, the same blood-building strategy can become too much, tipping a useful response into disease.<\/p>\n Once blood gets overly crowded with cells, it flows sluggishly and tissues start losing the oxygen<\/a> they were meant to gain.<\/p>\n The worst form of this condition is called chronic mountain sickness, a long-term illness that can appear after years of high-altitude living.<\/p>\n That burden helps explain why adaptation is never simple improvement, because a solution can injure the body it protects.<\/p>\n Oxygen for a growing fetus<\/p>\n Before anyone reaches adulthood, altitude can already reshape survival through pregnancy, birth, and childhood oxygen supply.<\/p>\n In Andean pregnancies, stronger uteroplacental blood<\/a> flow \u2013 blood movement from mother to placenta \u2013 helps send more oxygen to a growing fetus.<\/p>\n That extra flow appears to protect birth weight better than short stays at altitude do, even when the air stays thin.<\/p>\n Early development therefore matters twice, first by shaping the body itself and later by influencing how well adult systems cope.<\/p>\n Human bodies evolve in subtle ways<\/p>\n Cases like the Sama-Bajau and Tibetan highlanders show that human evolution did not stop in the distant past.<\/p>\n Strong local pressures can still favor traits that help<\/a> families survive, work, and raise children in one demanding place.<\/p>\n Behavior starts the process, but over many generations genes and development can lock some advantages more deeply into the body.<\/p>\n That mix of culture, environment, and biology makes human diversity easier to understand without turning it into a ranking.<\/p>\n Across oceans and mountains, the same pattern appears: the body meets a recurring lack of oxygen by changing structure, blood, and behavior.<\/p>\n What looks like a human limit often becomes a local specialty, though every gain still comes with a cost.<\/p>\n The study is published in the journal Cell<\/a>.<\/p>\n \u2014\u2013<\/p>\n Like what you read?\u00a0Subscribe to our newsletter<\/a>\u00a0for engaging articles, exclusive content, and the latest updates.<\/p>\n Check us out on\u00a0EarthSnap<\/a>, a free app brought to you by\u00a0Eric Ralls<\/a>\u00a0and Earth.com.<\/p>\n \u2014\u2013<\/p>\n","protected":false},"excerpt":{"rendered":"People who spend much of their lives diving for food have evolved unusually large spleens that release extra…\n","protected":false},"author":2,"featured_media":390277,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[85,46,141],"class_list":{"0":"post-390276","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-science","8":"tag-il","9":"tag-israel","10":"tag-science"},"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/posts\/390276","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=390276"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/posts\/390276\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/media\/390277"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/media?parent=390276"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/categories?post=390276"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/il\/wp-json\/wp\/v2\/tags?post=390276"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}