How did dinosaurs evolve into birds?
How birds evolved from dinosaurs is a 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 could study.
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 is the oldest bird and was diagnosed as the first bird. Looking at it today, scientists would say it is a feathered dinosaur instead of a bird.
Archaeopteryx had specialized feathers for flight. But it also had teeth, a long tail, the 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 evolved into the small-bodied birds. Not all dinosaurs 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 the feathers for insulation. They didn’t evolve feathers to fly. The feathers then were later adapted to other things like sheltering eggs or nests, and then ultimately used for dynamic structure.
Imagine you have a little bit of a wing feather on your arm and you’re running really fast. If you throw your arm out, it induces a drag, which causes you to turn really quick. You throw both arms out, and you start to fly a little bit.
All of those things add up to sequential steps in which feathers were ultimately adapted for flight, but weren’t originally meant for flight.