MacKinnon has ranged the planet of the apes, doing field observations of gibbons, siamangs, gorillas, Goodall's chimps, bonobos, and the orang-utans he limned in the 1974 In Search of the Red Ape. Here he's on the prowl for ""apeliness,"" looking for commonalities within ape societies, less consistent than monkey groupings, and between apes and men. In terms of social, sexual, and anatomical similarities, the orang-utan emerges as man's most probable ape ancestor, but biochemistry, fossil evidence, and other measures point to the chimp and gorilla as more like man. Most literate bipeds will swing right along with all of this--remember how many people recognized The Naked Ape--but when MacKinnon turns to Man (technology, family, and community structure) the generalizations get a lot trickier, and his theories on related sexual differences are sure to receive a careful going over. He maintains that climatic and geological pressures forced forest apes into major changes, including a diet of seeds and tubers, upright posture (enabling limited tool use), and cooperative hunting formations. Within this evolutionary context, human pair-bonds, unlike ape pair-bonds, become problematic, ""more in the female's interest than the male's, and it is this basic inequality that has led to much of the socio-sexual strife in our society."" Comparing ape and human behaviors is always chancy but MacKinnon's comparisons are especially heady and will certainly kindle lots of fireworks. Within the territory, he falls somewhere between Ardrey and the social anthropologists: ""We are all equipped with the body, glands, and brain that allow us to develop whatever levels of aggression are most suitable to our circumstances, but we also have high levels of perceptiveness so that we can evaluate how appropriate aggressive behavior would be in any situation. . . ."" Thumbs up?