Birds are famous for their colorful feathers, which they use to fly, flirt, and keep warm. But have you ever imagined, what came first, birds or feathers?
Now, a new study discovered that feathers arose 100 million years before birds, changing our understanding of feathers themselves, their functions and their role in some of the most significant events in evolution.
New research, led by the University of Bristol, combines new information from paleontology and molecular developmental biology. It found that feathers did not originate with birds, it arose before them, maybe even before dinosaurs themselves.
In the evolutionary tree, the dinosaurs with feathers were much more closely related to the origin of birds, according to the University of Bristol.
The key discovery came earlier in 2019 when feathers were reported in pterosaurs (an ancient reptile). If the pterosaurs really carried feathers, it means these structures arose deep in the evolutionary tree – much deeper than at the point when birds originated.
“The oldest bird is still Archaeopteryx first found in the Late Jurassic of southern Germany in 1861, although some species from China are a little older,” says Bristol professor Mike Benton, the lead author. “Those fossils all show a diversity of feathers – down feathers over the body and long, vaned feathers on the wings. But, since 1994, paleontologists have been contending with the perturbing discovery, based on hundreds of amazing specimens from China, that many dinosaurs also had feathers.”
“This was not so hard to believe. So, the origin of feathers was pushed back at least to the origin of those bird-like dinosaurs, maybe 200 million years ago,” added co-author, Baoyu Jiang from the University of Nanjing.
“This dinosaur showed amazingly well-preserved skin covered with scales on the legs and tail and strange whiskery feathers all over its body,” recalls co-author Maria McNamara from University College Cork.
“What surprised people was that this was a dinosaur that was as far from birds in the evolutionary tree as could be imagined. Perhaps feathers were present in the very first dinosaurs.”
Danielle Dhouailly from the University of Grenoble, also a co-author, works on the development of feathers in baby birds, especially their genomic control. “Modern birds like chickens often have scales on their legs or necks, and we showed these were reversals: what had once been feathers had reversed to scale,” she said. “In fact, we have shown that the same genome regulatory network drives the development of reptile scales, bird feathers, and mammal hairs. Feathers could have evolved very early.”
The breakthrough actually came when researchers were studying two new pterosaurs from China. Once considered scaly and reptilian, these prehistoric flying reptiles (closely related to dinosaurs), were covered in four kinds of tuft and down. Pterosaurs, it would seem, had feathers remarkably similar to their dinosaur relatives. They must have had a common ancestor.
“This drives the origin of feathers back to 250 million years ago at least. The point of origin of pterosaurs, dinosaurs and their relatives,” Professor Benton added. “The Early Triassic world then was recovering from the most devastating mass extinction ever, and life on land had come back from near-total wipe-out.”
“Palaeontologists had already noted that the new reptiles walked upright instead of sprawling, that their bone structure suggested fast growth and maybe even warm-bloodedness, and the mammal ancestors probably had hair by then.”
“So, the dinosaurs, pterosaurs and their ancestors had feathers too.” Feathers probably arose to help in the content, providing insulation in the warm-blooded precursors of dinosaurs and pterosaurs. The other functions of feathers, for display and of course for flight, came much later.
The new work published in the journal Trends in Ecology & Evolution.