After the extinction of the dinosaurs, some birds decreased in size and kept large brains

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Indeed, new research suggests that some birds have evolved over time to have smaller bodies and maintain large brains.

Researchers studied the endocasts of skulls belonging to hundreds of extinct dinosaurs and birds.

They used CT scans of ancient animal skulls to create endocasts, which act like a brain imprint in the skull, reflecting the size of the brain (because brains don’t fossilize). Then they compared the size of the brain with measurements of the brains of modern birds in a large dataset.

Brain measurements were analyzed with body size to compare the scale of brain size to body size.

Together, evolutionary biologists and paleontologists were able to show the chronology of the evolution of the birds’ brains. The study was published Thursday in the journal Current Biology.

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Before the mass extinction event that killed dinosaurs 66 million years ago, researchers discovered that birds and large dinosaurs had brains of very similar size.

But some birds have gone through what researchers call a “scale-up” event after the dinosaurs went extinct.

These visuals show brain (blue) endocasts of the skulls of a dinosaur and a modern bird.

Birds were among the first animals to recover and repopulate the empty landscape after the disappearance of the dinosaurs. They have diversified and evolved in this context, and some of the birds that started larger have known what is called “downscaling”. Their bodies shrank in size, but they kept the big brains of their larger ancestors.

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“Our article highlights that mass extinction has really changed the course of the avian brain,” said Daniel Ksepka, lead study author and curator of science at the Bruce Museum, in an email to CNN.

“There have been profound changes in the scaling of the brain and body in the aftermath of extinction, and these may have played an important role in the survival of modern birds and their irradiation to more of 10,000 species that we have today. “

The changes seem to happen very quickly after the impact of the asteroids that caused the dinosaurs to go extinct, Ksepka said. They found at least seven events of scaling of the brain and body in birds immediately after the mass extinction.

Before the mass extinction event, the similarities between the brains of dinosaurs and birds were almost indistinguishable.

“There is no clear line between the brains of advanced dinosaurs and primitive birds,” said Amy Balanoff, study co-author and research assistant professor in the Department of Psychological and Cerebral Sciences at the University. Johns Hopkins, in a statement.

“Birds like emus and pigeons have the same brain sizes as you would expect from a theropod dinosaur of the same body size, and in fact, some species like the moa have smaller brains than expected. “

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The event of mass extinction likely triggered these changes. These birds had to evolve to survive.

“In the aftermath of the impact of the asteroids, it would have been extremely difficult to survive,” said Ksepka. “Larger-brained animals tend to have more flexibility to adapt to changing environments.

“Likewise, smaller animals seem to have had a better chance of surviving in the immediate aftermath because they need less food. Thus, the altered landscape may have triggered the rapid evolution of new brain and body scaling patterns by favoring both larger brains and smaller bodies. ”

This Eurasian jay is part of the family of large brain birds called corvids.

The largest evolutionary leap of the brain is evident in modern birds such as parrots and corvids, the group which includes crows, crows and other related birds. And their brains are quite large relative to their body size, although crows and parrots are relatively large birds. Ravens are “particularly turbocharged” when it comes to brain capacity, said Ksepka.

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This may explain why they are able to recognize and remember human faces, use tools and even speak, as parrots do. In fact, crows and crows seem to correspond to our own evolutionary history as well as to certain behaviors that we associate with humans, said Ksepka.

“Like our hominin [ancient human ancestor] lineage, these birds have evolved to have both larger brains and larger bodies, “said Ksepka. The size of the brain has grown faster than the size of the body, leading to large, intelligent birds. Just like we ended up being big (sometimes) intelligent primates. “

“Crows are really off the charts – they have outpaced all other birds,” said Adam Smith, study co-author and curator of the Bob Campbell Geology Museum at Clemson University, in a statement. “Our results suggest that calling someone a ‘bird’s brain’ is actually a compliment! “

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