Primate brain evolution. Conceptual computer artwork of a brain (centre) with a monkey head (left) and a human head (right), representing the evolution of primate brains. Monkeys and humans are both primates, mammals that have good eyesight and flexible hands and feet. Both descend from a common ancestor, but have evolved differently. Their brains are similar, but humans have complex language and reasoning abilities. They also have highly developed technology, populate most of the land areas of the globe, are exploring surrounding space, and have scientific theories to explain the world around them. Monkeys live in jungles where they hunt and forage for food.