Human Sperm Competition

Sperm competition occurs when a female copulates with two or more males within a sufficiently brief time period, resulting in the sperm of the different males competing to fertilize ova. In this chapter, we present the evidence of sperm competition in humans. We review the literature indicating anatomical, psychological, and physiological adaptations to human sperm competition. These adaptations include traits that produce prudent sperm allocation, copulatory interest, forced in-pair copulation, sexual fantasy, female orgasm, and semen-displacing copulatory behavior. Given the evidence of apparently convergent adaptations to sperm competition in humans and nonhumans, we conclude that sperm competition has been a important selection pressure that shaped human nature. Keywords: sperm competition; humans; evolutionary psychology; comparative psychology