Promiscuity: An Evolutionary History of Sperm Competition.

TIM BIRKHEAD

If you still subscribe to the Darwinian notion of sexual competition, which holds that only males are promiscuous by nature while females lean toward monogamy, then you are woefully behind the advances in the field of sexual physiology and selection, Birkhead believes. He systematically debunks this concept by revealing the sexual habits of scores of animals and specifically the promiscuous nature of females. He focuses on not only the process of acquiring a mate but also what happens after insemination takes place. This two-part story revolves around the competition between the sperm of different males to fertilize a female's eggs and the choice exercised by a female, through sometimes aggressive means, to determine the best sperm for her eggs. Birkhead describes tiny flies whose seminal fluid is so toxic that it not only destroys the sperm of rival males but also can kill the female. Human behavior such as wife sharing is also a manifestation of sperm competition, the author contends. Originally published in hardcover in 2000. HUP, 2002, 272 p., color plates/b&w illus., paperback, $16.95