Possible evolutionary origins of human female sexual fluidity

Abstract

I propose an evolutionary theory of human female sexual fluidity and argue that women may have been evolutionarily designed to be sexually fluid in order to allow them to have sex with their cowives in polygynous marriage and thus reduce conflict and tension inherent in such marriage. In addition to providing an extensive definition and operationalization of the concept of sexual fluidity and specifying its ultimate function for women, the proposed theory can potentially solve several theoretical and empirical puzzles in evolutionary psychology and sex research. Analyses of the National Longitudinal Study of Adolescent Health (Add Health) confirm the theory's predictions that: (i) women (but not men) who experience increased levels of sexual fluidity have a larger number of children (suggesting that female sexual fluidity, if heritable, may be evolutionarily selected); (ii) women (but not men) who experience marriage or parenthood early in adult life subsequently experience increased levels of sexual fluidity; and (iii) sexual fluidity is significantly positively correlated with known markers of unrestricted sexual orientation among women whereas it is significantly negatively correlated with such markers among men.

Father absence, sociosexual orientation, and same‐sex sexuality in women and men

“…Furthermore, Columns 3 and 4 show that, consistent with the prediction, father absence was not associated with adult sexual identity among men. Furthermore, consistent with earlier findings (Kanazawa, ), the number of opposite‐sex partners was significantly positively associated with same‐sex identity among women, whereas it was negatively associated among men.…”

“…192–194; de Waal, ). Further consistent with the theory, the quantitative empirical analyses show that sexually more fluid women are reproductively more successful, suggesting that female sexual fluidity may have been evolutionarily selected, and that the experience of marriage and parenthood early in adulthood increases women's sexual fluidity later in adulthood (Kanazawa, , pp. 1265–1267).…”

“…It is also consistent with the earlier finding that women with high sex drives are sexually attracted to both men and women, whereas men with high sex drives are sexually attracted only to women (if they are straight) or only to men (if they are gay) (Lippa, ). While this model cannot explain exclusive lesbians, Kanazawa (, p. 1267) shows that only 0.3% of American women belong in this category.…”

“…Following the ground‐breaking work of Diamond (, ) and Bailey (), Kanazawa () has recently proposed an evolutionary theory of female sexual fluidity . The theory proposes that, given the human evolutionary history of mild polygyny, women may have been evolutionarily designed to be sexually fluid so that they could occasionally have sex with their cowives to reduce conflict and tension common among cowives of nonsororal polygynous marriages while at the same time maintaining their heterosexual relationships with their husband for the purpose of reproduction.…”

“…The theory proposes that, given the human evolutionary history of mild polygyny, women may have been evolutionarily designed to be sexually fluid so that they could occasionally have sex with their cowives to reduce conflict and tension common among cowives of nonsororal polygynous marriages while at the same time maintaining their heterosexual relationships with their husband for the purpose of reproduction. There is ethnographic evidence from Africa, Imperial China and the United States (among fundamentalist Mormons) that cowives occasionally have sex with each other (Kanazawa, , pp. 1261–1264) and primatologists have observed that female bonobos engage in genitogenital rubbing to reduce tension and build alliances with other females (Furuichi, , pp.…”