Why do people have sex? Is it solely for the purpose of passing on genetic information, or are there other reasons? "A candid, no-punches-pulled interpreter of the core ideas of evolutionary biology" (Science News), author Niles Eldredge unravels the origins of our coital instincts. Whereas other scientists dismiss human sexuality as a helpless response to the same deep-set biological imperatives that govern the behavior of lesser animals, Eldredge points to various examples of customs, taboos, laws, and other cultural forces that run counter to our most primal desires. Directly assaulting the reductionist "selfish gene" theory, whereby sex is reduced to a purely procreative act, Eldredge draws on Darwin's ideas about evolution as well as modern economic theory to describe the delicate cultural and societal interaction that exists between survival, sex, and procreation in the human species.