Sexual rivalry is a major cause of violence. Most violent deaths are of men killed by other men. In these cases, there is usually a dispute over loss of status, or "face." However, violent deaths also extend to women killed by men. In such cases, violence can be considered one strategy in a suite of male coercive tools. Most such coercion results from sexual proprietariness. Men who are cuckolded are losers of the zero-sum evolutionary game of getting their genes into the next generation (Wilson & Daly, 1996). Whereas maternity is never in doubt, paternity involves a bit of strategy and guesswork (hence the saying "mommy's baby, daddy's maybe"). Men use violence to keep their mates from engaging sexually with other men.

Within-family violence occurs not only toward mates, but also toward step-children. Step-fathers have no adaptive interest in the survival of their (genetically unrelated) step-children. Indeed, supporting another man's child with one's own resources contravenes a man's evolutionary interests. Therefore, we should expect that men would be much more likely to commit violence, even murder, against their step-children than against their biological children. The figures in support of this hypothesis are stunning. Whereas abuse of step-children is seven times higher than abuse of biological children, fatal abuse is 100 times higher (Daly & Wilson, 1996).


Daly, M., & Wilson, M. I. (1996). Violence against step-children. Current Directions in Psychological Science, 5, 77-81.

Wilson, M. I., & Daly, M. (1996). Male sexual proprietariness and violence against wives. Current Directions in Psychological Science, 5, 2-7.

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