Snake Threat May Have Spurred Evolution of Primate Eyes

The ability to detect threatening snakes may have shaped the visual system of our primate ancestors, a new study says.

In a sort of evolutionary arms race, primates kept improving their eyesight to help spot and avoid snakes as the snakes became more dangerous, suggests Lynne Isbell, a behavioral ecologist at the University of California, Davis.

The initial change in primate [eyes] ... occurred when they had to deal with constricting snakes, probably about 90 million years ago, Isbell said.

That ended up with primates that have forward-facing eyes, whereas other mammals tend to have eyes on the sides of their heads. Forward-facing eyes allow better depth perception.