Sixty-five million years ago, an asteroid is believed to have crashed into Earth. The impact wiped out huge numbers of species, including almost all of the dinosaurs.
One group of dinosaurs managed to survive the disaster. Today, we know them as birds.
The idea that birds evolved from dinosaurs has been around since the 19th century, when scientists discovered the fossil of an early bird called Archaeopteryx. It had wings and feathers, but it also looked a lot like a dinosaur. More recent fossils look similar.
But these early birds didn't look the same as modern ones. In particular, they didn't have beaks: they had snouts, like those of their dinosaur ancestors.