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In general, males are the high rollers in the sex game. They take greater risks than females (death in combat over a female, exclusion from breeding by a stronger male), but they also have more to gain (spreading their genes far and wide). Still males have one overpowering disadvantage—they can never be sure that the offspring are their own. A cuckolded male is a biological loser, tricked into investing his time and energy in another male's genes. Thus sexual jealousy evolved among monogamous males as an adaptation. So did courtship rituals. By monopolizing a female's time, but not copulating, a courting male waits long enough to make certain that the female is not already pregnant. Among ring doves, a male turns from wooing to aggression if the female responds to his courtship too soon; that is a good sign that she may be pregnant.
For females, coy behavior makes sense if it elicits some sign of good genes or commitment to nurturing. Sociobiologists believe estrus disappeared in humans as a female strategy to cement monogamy: a year-round sexual attractiveness helped keep mates from wandering off. Menopause may have evolved to turn aging females away from breeding and toward protecting their genetic investment by caring for grandchildren.
Sociobiologists think that evolution has produced different physiques, behavior and attitudes in males and females—a touchy subject for feminists. Trivers says the female is not equipped for the chase and shows no interest in it. And Edward Wilson reminds readers that in the million-year hunter-gatherer period of evolution, men hunted and women stayed home. Adds Wilson: "This strong bias persists in most agricultural societies, and on that ground alone appears to have a genetic origin."
Comments like these have irritated some campus feminists, who fear sociobiologists are telling them to stay home and mind the babies, but Sociobiologists have some calming news: hunter-gatherer women were economic equals. Says DeVore: "The female is an absolutely integral part of the society, because only her gathering makes it possible for the male to indulge in the gamble of the hunt." Sociobiologists stress that the sexes are genetically equal and can evolve different strategies as conditions change.
It has been argued that the rise of feminism could be a genetic adaptation. Robert Trivers, however, has a sobering thought: if more feminists take jobs and have fewer children, more of the child-bearing may be left to nonfeminists. In evolutionary terms, this would mean that feminism is being selected against and will either die out entirely or start from scratch in every generation.