How chimpanzees cooperate in a competitive world

Competitive tendencies may make it hard for members of a group to cooperate with each other. Humans use many different "enforcement" strategies to keep competition in check and favor cooperation. To test whether one of our closest relatives uses similar strategies, we gave a group of chimpanzees a cooperative problem that required joint action by two or three individuals. The open-group set-up allowed the chimpanzees a choice between cooperation and competitive behavior like freeloading. The chimpanzees used a combination of partner choice and punishment of competitive individuals to reduce competition. In the end, cooperation won. Our results suggest that the roots of human cooperation are shared with other primates.