When Men Behave Badly: The Hidden Roots of Sexual Deception, Harassment, and Assault

by David M. Buss

Although there is considerable overlap, men’s jealousy focuses more heavily on the sexual aspects of their partner’s conduct. It does so for an extremely important functional reason. It evolved to solve the problem of paternity uncertainty. Women are always 100 percent certain that they are the mothers of their offspring. No woman ever wondered, as an infant was emerging from her body, “Is this kid really mine?” Men can never be sure. As people in some cultures say, “Mama’s baby, Papa’s maybe.” It’s an asymmetry that stems directly from an asymmetry of human reproductive biology—fertilization occurs internally within the woman’s body, not the man’s. And unless a woman is under lock and key twenty-four hours a day guarded by a phalanx of eunuchs, another man might have the opportunity to inseminate her.