Abstract and Keywords
This review explores whether and how imbalances in the number of men and women—the sex ratio—affects mating competition. I evaluate the available evidence against two hypotheses: a mating supply and demand hypothesis, which predicts mate competition to increase when mates are scarce, and predictions from a ‘faithful as your options’ hypothesis, which suggests mate competition should increase with a surplus of mates because the returns to mating effort are greatest. Men’s mating effort consistently increased with a surplus of mates, supporting the ‘faithful as your options’ hypothesis, but results for women’s mating effort were mixed. Some measures supported the mating supply and demand hypothesis, some supported the ‘faithful as your options’ hypothesis, and some found no relationship with the sex ratio. Socioeconomic development may explain variation in sex ratio effects for women if men are better able to constrain women’s mating effort in traditional societies, or other variables, like variation in mate quality, may better explain women’s mate competition.
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