The asteroid that struck the Yucatán 66 million years ago wreaked worldwide ecological damage, spelling the end for most dinosaurs and destroying the world’s forests. Yet a few bird-like dinosaur groups made it through. Scientists believe that these groups were all ground-dwellers. Though some species could fly, a life on the ground would have been a key advantage in a world without forests. All modern birds evolved from these ancient creatures. Learn more at BirdNote.org.