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Birds' hips don't lie: Their embryonic bones tell of their dinosaur past

image by Martin Schubert from Pixabay

Birds’ bones, specifically their hips, tell the story of their evolution from dinosaurs before they’re even born according to a new Yale University study.

Bhart-Anjan Bhullar, the assistant professor of Earth & Planetary Sciences and assistant curator of Vertebrate Paleontology and Vertebrate Zoology at Yale University, said every bird goes through a mini-evolution before they’re even born. As their embryos develop, their hips take the form of the dinosaurs they used to be before becoming more birdlike.

“And they don't even start off with a dinosaur-like pelvis," Bhullar said. "Birds as early embryos start off with a pelvis that look very much like those of early reptiles that are even more primitive, far more primitive, in fact, than dinosaurs.”

Bhullar said from there, birds’ hips grow in the same order in which they evolved. For a minute they look like a tyrannosaurus, then a velociraptor, and so on. So it’s almost like birds are replaying their own evolutionary history while they’re still in the egg.

“Inside this little microcosm, this little world that is the egg, every single bird marches through its past, until almost at the last second as a very late embryo, it suddenly remembers, 'oh my God, I'm a bird',” Bhullar said.

Bhullar adds that scientists assumed these dinosaur skeletal features were lost — on display in museums possibly but gone from the modern tapestry of life.

“We didn't think there was anything alive that expressed that — ever — anytime in its existence," said Bhullar. "And so there are in fact, in a hidden way, inside the egg, these forms thought long vanished.” 

Which means — deep in their genomes — birds may still carry detailed instructions on how to build a dinosaur.

Davis Dunavin loves telling stories, whether on the radio or around the campfire. He started in Missouri and ended up in Connecticut, which, he'd like to point out, is the same geographic trajectory taken by Mark Twain.