Demonic Males: Apes and the Origins of Human Violence is a 1996 book by Richard Wrangham and Dale Peterson examining the evolutionary factors leading to human male violence. Summary Demonic Males begins by explaining that humans, chimpanzees, gorillas and orangutans are a group of genetically related great apes, that humans are genetically closer to chimps than chimps are to gorillas, and that chimps and bonobos are most closely genetically related. After speculating about what enabled humans' ancestors to leave the rainforest (the use of roots as sources of water and food), Demonic Males next provides a catalog of the types of violence practiced by male chimpanzees (intragroup hierarchical violence, violence against females, and extragroup murdering raids). The high incidence of rape by non-alpha male orangutans and infanticide by male gorillas are also cited as examples of our mutual genetic heritage. The authors present chimp society as extremely patriarchal, in that no adult male chimpanzee is subordinate to any female of any rank. They present evidence that most dominant human civilizations have always been likewise behaviorally patriarchal, and that male humans share male chimpanzees' innate propensity for dominance, gratuitous violence, war, rape, and murder. They claim that the brain's prefrontal cortex is also a factor, as humans have been shown experimentally to make decisions based both on logic and prefrontal cortex-mediated emotion. To contrast chimp societies, in the chapter "The Peaceful Ape", the authors contrast chimpanzee behaviors with those of the bonobo, presenting logical biological reasons for the more pacific (although also aggressive and antagonistic) behaviors of the latter. Reasons given for this include a bonobo female social organization that does not tolerate male aggression, the evolutionary forces of the invisibility of bonobo ovulation (in chimps, ovulation has both olfactory and genital swelling manifestations. This diversity in female reproductive cycles then leads to ferocious male competition for mating), and overall social organization, whereby male bonobos do not form alliances as male chimps do, though this has been contested. Bonobos are dominated by a matriarchal system, and are unique for their female-biased dispersal relationships that encourage resolution and peace-making tactics among the group, and discourage violence and war. Anthropological parallels can be made to human subcultures such as the Hippies, expressed in the motto that Hippies and Bonobos make love, not war. Anthropologists using post modern perspective try to explain how Bonobo social structure rejects aggression and focuses on the power of