High in the mountains of Ethiopia lives a primate unlike any other. The Gelada may resemble a baboon, but it is not a baboon. It is the only primate that feeds almost entirely on grass, spending most of the day plucking blades with its nimble fingers on the cool alpine slopes.

Geladas live in complex societies where hundreds of individuals can share the same hillside. Keeping peace in such massive groups depends on constant communication. Instead of fighting, they use expressions and sounds to navigate daily life. A raised brow, a gentle grimace, or the famous lip flip can all shift the mood of the group in seconds.