Sperm Wars turns the conventional thinking about the biology of sex on its head. Evolutionary biologist Robin Baker argues that human sexuality follows certain laws, and all of those laws are governed by one thing: sperm warfare. In the interest of promoting competition between sperm to fertilize the same egg, evolution has built men to conquer and monopolize women while women, without ever knowing they are doing it, seek the best genetic input on offer from potential sexual partners. In this book, Baker reveals, through a series of provocative fictional scenes, the far-reaching implications of sperm competition: ten percent of children are not fathered by their ‘fathers;’ less than one percent of a man’s sperm is capable of fertilizing anything (the rest is there to fight off all other men’s sperm); ‘smart’ vaginal mucus encourages some sperm but blocks others; and a woman is far more likely to conceive through a casual fling than through sex with her regular partner. From infidelity, to homosexuality, to the female orgasm, Sperm Wars turns on every light in the bedroom. Two decades after its initial publication, this classic of popular science will still surprise, entertain, and even shock.