A sparkling set of essays by MacArthur awardee Sapolsky (Why Zebras Don't Get Ulcers, 1993; Biology and Neuroscience/Stanford), who is not at all afraid to go out on a (primate) limb to discuss biology, brain, and behavior. As a veteran baboon watcher, he has much to say on stress and hormones, adolescence, and other fascinating topics. In some essays he is merely out to set the record straight. So we learn in the title essay that higher testosterone levels do not increase aggression, but that aggression increases testosterone levels. Even if you give massive amounts of hormone to a monkey who, let us say, is number three in a dominance hierarchy, he will tyrannize numbers four and five but still kowtow to the two above him. Other baboon-based essays become springboards for discussion of commonalities between them and us, for example, in voyeurism: Baboons like to watch, too. They are easy targets for junk food, and adolescence is a markedly stress-filled period in which male baboons appear to be programmed to leave the troop and join another, invariably as low man on the totem pole. In other essays Sapolsky makes perturbing leaps: Are the sundry neurological disorders he glibly describes (epilepsy, Huntington's disease, Tourette's syndrome, obsessive-compulsive disorder) truly representative of a continuum of behavior? Are the founders and leaders of religion ""schizotypal"" personalities? Arguable, certainly, but always interesting. Elsewhere Sapolsky, who summers in Kenya, writes of the predicament of the African middle class--infatuated with Western diets and cultures while trapped in the persistent rhythms of the old ways. In the end it is the refreshing honesty of this scientist-teacher, his zeal to speculate as well as to clearly present the facts, that engages the reader. That, and a deft and often witty way with words.