A ten year study of Ugandan chimps has documented violent territory struggles between rival camps, but what impresses researchers is the cooperation needed to carry out the attacks. “Dr. Mitani, however, is reluctant to infer any genetic link between human and chimp warfare, despite the similarity of purpose, cost and tactics. ‘It’s just not at all clear to me that these lethal raids are similar sorts of phenomena,’ he said. More interesting than warfare, in his view, is the cooperative behavior that makes war possible. Why do chimps incur the risk and time costs of patrolling into enemy territory when the advantage accrues most evidently to the group?”