Q How did dinosaurs evolve into birds?
— Noah Schwab, Two Rivers, Wis.
A Dave Lovelace, vertebrate paleontologist at the University of Wisconsin-Madison Geology Museum:
How birds evolved from dinosaurs is a dinosaur paleontology question that extends all the way back to the late 1800s.
After Charles Darwin published his “Origin of Species” in 1859, one of his friends and colleagues, Thomas Henry Huxley, came up with an idea. He noticed that early dinosaurs have a lot of bird-like characteristics, and Huxley had modern birds he was studying. He noticed how similar the early dinosaurs were to birds but couldn’t exactly identify the relationship.
One year later, the very first specimen of Archaeopteryx was found. Archaeopteryx has been determined to be the first bird.
Archaeopteryx looks like a feathered dinosaur instead of a bird. It had specialized feathers for flight, but it also had teeth, a long tail and a little sickle claw — everything that makes it look like a small velociraptor or a dromaeosaur.
Over the last 20 or 30 years scientists have been finding an amazing array of fossils all over the world, many of them coming from lake beds in China. Those specimens are all feathered. There was even a specimen found in 2016 preserved in amber that had the tailbones of the dinosaur. On those tailbones was a fully preserved feathered tail.
All of these things line up to show us the relationships between birds and meat-eating dinosaurs.
It’s not the Tyrannosaurus rex necessarily, but a related group like the dromaeosaurs that evolved into small-bodied birds. Not all of them were big. In fact, the smallest ones are the ones that are still alive today.
The one big question is: How exactly did flight evolve? Scientists know that dinosaurs almost certainly had feathers for insulation. They didn’t evolve feathers to fly. The feathers were initially adapted for other things like sheltering eggs or nests.
There were sequential steps in which feathers were ultimately adapted for flight, but they weren’t originally meant for flight.