He has conducted extensive research on primate ecology, nutrition, and social behavior. He is best known for his work on the evolution of human warfare, described in the book Demonic Males, and on the role of cooking in human evolution, described in the book Catching Fire: How Cooking Made Us Human. Together with Elizabeth Ross, he co-founded the Kasiisi Project in 1997, and serves as a patron of the Great Apes Survival Partnership (GRASP).