Forget Rousseau. Forget Konrad Lorenz. Wrangham and Peterson say that after 40 years of gorilla and chimpanzee watching, it is hard not to conclude that human males are but evolutionary heirs of male ape aggression. Our primate male cousins gang up to murder and rape, expand their territory (and genes), and fight to get to the top. But at the same time that MacArthur fellow Wrangham (Biological Anthropology/Harvard) and Peterson (Jane Goodall's coauthor on Visions of Caliban) present overwhelming (and depressing) evidence of male mayhem from observations in the wild, from history, from ethnography and politics, they are not die-hard biological determinists. Bigger brains and the development of language, moral codes, justice systems, and democratic governments can be countervailing elements. Very importantly, so can females. Indeed, the most hopeful chapter in the book documents 20 years of watching bonobo chimpanzees of Zaire. Male-female equality is the rule among bonobos, and life appears to be positively tranquil--no raids and murders, no rapes or sexual jealousies, no in-group-out-group aggression. Doubting Thomases may well take a wait-and-see attitude, but the authors suggest ecological reasons favoring development of these ``gentle'' apes: better food supplies enabling movements of larger parties, for example, leaving fewer chances to gang up on isolated individuals. They particularly credit strong mother-son bonds and powerful female cooperation. Is there a lesson there, too? The authors suggest there could be a hopeful future if democratic governments can evolve away from patriarchal dominance to greater shared power. But poised as we are on the technological brink of self-destruction, the authors argue that we will need all the powers of human intelligence to counter the demonic urges. To their credit, they have presented a powerful and moving account of the human condition that is as absorbing as it is sobering. It deserves a wide audience.