They share the same 'ancient roots,' but why can birds fly while crocodiles can't? Scientists finally have the answer.

Crocodiles and birds originated 250 million years ago from a common ancestor. Scientists now believe the crocodile lineage was originally warm-blooded before reverting to a cold-blooded metabolism. This change likely saved them from extinction 66 million years ago. Today, their low metabolic rates mean they simply cannot fly like birds.