Snakes evolved around 150 million years ago from burrowing lizards, leaving some of the more primitive snake species alive today with vestigial hind legs. A fossil from northwest India shows a snake, Sanajeh indicus, eating a titanosaur dinosaur egg 67 million years ago.

For over 60 million years, snakes have lived in many of the same environments as humans and their ancient ancestors, posing a tangible threat. Early humans had a pressing need to detect and avoid snakes and that likely put evolutionary selection pressure on humans to evolve forward-facing eyes and large visual centers in the brain. Recent research suggests that this equipped humans with the ability to pick up more readily on certain shapes, like the general shape of a snake’s body in a camouflaged setting.