The two chimpanzee species, the common chimp and the bonobo, may both be closely related to humans, yet they are rather different from each other behaviorally. Chimpanzee society is dominated by males, while among bonobos, females are dominant and there is less aggression. One illustration of the differences cited by scientists is that chimpanzees occasionally conduct group hunts for other primates while bonobos do not. The hunts, for tree-dwelling monkeys, seem to be more about male bonding and dominance than about nutrition, so it makes sense that the bonobos don’t do it. Except that new research shows that in fact they do.