Is Female Orgasm a Covert Mate Choice Mechanism?

Debate surrounds whether women's orgasm is an adaptation or a by-product of orgasm in men. We clarify what evidence would decide this debate and review evidence that female orgasm is an adaptation for promoting fertilization by men of high genetic quality. Female orgasm does not appear vestigial as by-products do. Rather, cross-species data suggest that female orgasm depends on the quality of a female's mate and evolves where females copulate polyandrously. Sex differences in human orgasm frequency mirror sex differences in choosiness over mates, and orgasm frequency tracks conception risk across the cycle, another indicator of a sire choice function. Manipulations of orgasm-related hormones and brain regions in humans and nonhuman mammals indicate that female orgasm promotes conception. We review evidence of men's concern over female orgasm in order to gauge paternity certainty, and evidence that women feign orgasm in order to maintain male investment.