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The birds are passerines<\/a> \u2013 the order of perching birds that includes sparrows, finches, warblers and crows. More than half of all living bird species belong to this single group. That sheer abundance makes it a natural place to study how body plans arise and change over long stretches of time.<\/p>\n Tracing that history meant measuring bones, and a lot of them. The team recorded more than 170,000 individual skeletal measurements across more than 2,000 species. Doing that by hand would swallow a career. So they used an AI tool called Skelevision. It photographs each specimen against a gridded background, which sets a common scale. Then it measures a dozen bones from the image.<\/p>\n The project was led by Jacob S. Berv<\/a>, a postdoctoral researcher at the University of Michigan (U-M<\/a>). He worked with senior author Brian Weeks, a U-M associate professor. Weeks\u2019 lab built Skelevision over seven years with a computer-vision group at New York University (NYU<\/a>).<\/p>\n The dataset\u2019s size stands out. \u201cI think the sheer scale of this kind of dataset is somewhat unprecedented in this field of science,\u201d Berv said in an email to Earth.com.<\/p>\n Most of the roughly 15,000 museum specimens<\/a> came from the U-M Museum of Zoology. Each scan takes about 45 seconds. At that pace, a drawer of skeletons that sat untouched for decades can be digitized in days.<\/p>\n Evolution came in rare bursts<\/p>\n Berv built a statistical method, named bifrost, that treats the whole skeleton as one connected system. It does not read each bone on its own. A longer wing tends to arrive with other changes elsewhere in the body. The model works out the sequence of those changes that could produce the birds alive today.<\/p>\n When run across the passerine family tree, the model returned a lopsided picture. Change did not trickle in at a steady rate. It clustered into a few rare, powerful bursts near the roots of major groups. <\/p>\n Between those bursts lay long, quiet spans of little change. Biologists had seen hints of this pulsed pattern in the fossil record. Seeing it laid out so plainly across a huge group of living birds is new.<\/p>\n Those bursts align with a century-old idea in biology. A lineage that reaches new territory can diversify fast into many forms. The same happens when one hits on a fresh way of making a living. Biologists call that process adaptive radiations<\/a>. The pace tends to slow as the open opportunities fill up.<\/p>\n \u201cThis is really important for evolutionary theory because there\u2019s a long history, going back 100 years, that predicts the emergence of new groups, called evolutionary radiations, is often associated with an explosive burst of diversification,\u201d said Berv.<\/p>\n The notion that environment leaves a mark on bird skeletons is not new. An earlier study<\/a> detected climate and habitat signals written into their shape. What this work adds is tempo \u2013 when the bursts fired, and how they track the state of the planet.<\/p>\n Climate drove bird evolution<\/p>\n The bursts also carry timestamps. Their strongest wave of change landed around 35 million years ago. That moment is known as the Eocene-Oligocene transition. The planet cooled sharply, and ice began to build at the poles.<\/p>\n A cluster of slowdowns followed around 15 million years ago, during another major change in the Miocene climate. The alignment is striking, though the study stops short of proving that the cooling caused the bursts. What it shows is that the tempo of evolution and the state of the climate rose and fell together.<\/p>\n Other work has pushed in the same direction. A large study<\/a> of birds and mammals found something similar. Body size evolved fastest during the cold spells of the last 66 million years, not the warm ones. Cold periods, it seems, speed the pace of change rather than slow it.<\/p>\n The rare, large speedups paired with many small slowdowns match a world where groups of birds keep finding new ecological room. They are \u201cexploring new ecological space and changing rapidly to take advantage of that opportunity,\u201d Weeks said.<\/p>\n Cold regions sped evolution<\/p>\n The team then turned from time to geography. They mapped the same skeleton data across the globe. It showed that where a bird lives predicts how fast its body shape evolves. Communities toward the poles, where temperatures swing hard between seasons, tend to hold faster-changing species. Those near the equator change more slowly.<\/p>\n That echoes earlier findings in birds. One paper<\/a> found that high-latitude bird species evolve certain traits faster than their tropical counterparts. The harsher climate swings they face appear to drive it. The new result stretches that idea from a few traits to the shape of the whole skeleton.<\/p>\n High-latitude species also showed a subtler difference. Their skeletons were more modular \u2013 different parts freer to change on their own rather than all together. That flexibility may let bodies respond faster when the environment turns unstable.<\/p>\n That whole-skeleton pattern had not been charted before. Asked by Earth.com about the study\u2019s other findings, Berv said, \u201cAs far as we know, this is the first time this global pattern has been documented in birds, and we think it may be a major discovery.\u201d<\/p>\n Weeks hopes the work will connect rates of body-shape change to one of ecology\u2019s oldest puzzles. Species pile up near the equator far more than at the poles, and no one fully knows why.<\/p>\n Clues for a warming world<\/p>\n Before this work, the pulsed nature of passerine evolution was mostly inference from scattered fossils. The skeleton measurements now put numbers on it. A few climate-linked bursts built most of the body-shape variety in the largest group of birds alive today.<\/p>\n That has implications for the present. The planet is warming fast, and biologists want to know how living things will answer. A record of how earlier upheavals reshaped bird bodies is one place to look for clues.<\/p>\n Pressed by Earth.com on today\u2019s warming, Berv said, \u201cSo, while this research doesn\u2019t make specific predictions about how birds might respond to today\u2019s rapid warming, it does tell us that unmitigated climate change, which persists for a long time, will have profound impacts on biodiversity.\u201d<\/p>\n The study also makes a quieter case for museum drawers. Those specimens were gathered over more than a century. No collector back then imagined a computer measuring them from a photograph. Their full value only became clear once the tools caught up. It is a strong argument for keeping such collections funded and growing.<\/p>\n The study is published in Nature Ecology & Evolution<\/a>.<\/p>\n Photo credit: Cody Limber\/Macaulay Library, courtesy of the University of Michigan.<\/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":"Perching birds evolved their body shapes in rare, sudden bursts that lined up with moments of upheaval in…\n","protected":false},"author":2,"featured_media":823991,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[64,63,128],"class_list":["post-823990","post","type-post","status-publish","format-standard","has-post-thumbnail","category-science","tag-au","tag-australia","tag-science"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/posts\/823990","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/comments?post=823990"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/posts\/823990\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/media\/823991"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/media?parent=823990"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/categories?post=823990"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/au\/wp-json\/wp\/v2\/tags?post=823990"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}