Father Absence, Sociosexual Orientation, and Same-Sex Sexuality in Women and Men

International Journal of Psychology International Journal of Psychology, 2020 Vol. 55, No. 2, 234–244, DOI: 10.1002/ijop.12569 Father absence, sociosexual orientation, and same-sex sexuality in women and men Satoshi Kanazawa Department of Management, London School of Economics and Political Science, London, UK A recent evolutionary theory of female sexual fluidity suggests that women may not have sexual orientations inthe same sense that men do, and that women’s apparent sexual orientation may instead be a byproduct of their sociosexual orientation. One developmental factor that has consistently been shown to influence sociosexual orientation is father absence in childhood. Consistent with the prediction of the theory, the analyses of the National Longitudinal Study of Adolescent to Adult Health (Add Health) data show that father absence significantly increases women’s, but not men’s, same-sex sexuality in adulthood, whether it is measured by self identity, sexual behaviour, or romantic attraction. Further consistent with the theory, the association between father absence and same-sex sexuality in women is entirely mediated by their sociosexual orientation. Keywords: Sexual fluidity; Homosexuality; Heterosexuality. Homosexuality presents perhaps the greatest theoretical fluidity.1 The theory proposes that, given the human evo- challenge to evolutionary psychology (Confer et al., lutionary history of mild polygyny, women may have been 2010), whose theoretical “bottom line” is reproductive evolutionarily designed to be sexually fluid so that they success. One of the first questions that evolution- could occasionally have sex with their cowives to reduce ary psychologists often receive as soon as they tell conflict and tension common among cowives of nonsoro- people—fellow academics and civilians alike—that they ral polygynous marriages while at the same time main- are evolutionary psychologists is “What about homo- taining their heterosexual relationships with their husband sexuality?” A series of popular introductions to the field for the purpose of reproduction. There is ethnographic have asked, and failed to answer, why homosexuality evidence from Africa, Imperial China and the United exists (Miller, 2000, pp. 217–219; Miller & Kanazawa, States (among fundamentalist Mormons) that cowives 2007, pp. 180–182; Wright, 1994, pp. 384–386). While occasionally have sex with each other (Kanazawa, 2017, male homosexuality has at least partly been explained pp. 1261–1264) and primatologists have observed that by the balancing selection hypothesis (Camperio-Ciani, female bonobos engage in genitogenital rubbing to reduce Corna, & Capiluppi, 2004; Iemmola & Camperio Ciani, tension and build alliances with other females (Furuichi, 2009; Rieger, Blanchard, Schwartz, Bailey, & Sanders, 1989, pp. 186–190; Vasey, 1995, pp. 192–194; de Waal, 2012; Schwartz, Kim, Kolundzija, Rieger, & Sanders, 1995). Further consistent with the theory, the quantita- 2010) and the fraternal birth order effect (Blanchard tive empirical analyses show that sexually more fluid & Bogaert, 1996; Bogaert, 2003; Cantor, Blanchard, women are reproductively more successful, suggesting Paterson, & Bogaert, 2002), there has not been compa- that female sexual fluidity may have been evolutionarily rable theoretical advances in the explanation of female selected, and that the experience of marriage and parent- homosexuality. hood early in adulthood increases women’s sexual fluidity Following the ground-breaking work of Diamond later in adulthood (Kanazawa, 2017, pp. 1265–1267). An (2007, 2008) and Bailey (2009), Kanazawa (2017) has analysis of the National Survey of Family Growth in the recently proposed an evolutionary theory of female sexual United States also shows that menopausal or otherwise Correspondence should be addressed to Satoshi Kanazawa, Department of Management, London School of Economics and Political Science, Houghton Street, London WC2A 2AE, UK. (E-mail: S.Kanazawa@lse.ac.uk). The author thanks Jay Belsky and Bruce J. Ellis for their comments on earlier drafts. 1Sexual orientation refers to whether the sex of preferred sexual partner is same-sex or opposite-sex, measured by self-identified labels, actual sexual behaviour, sexual feelings, and genital and brain responses (Mustanski, Chivers, & Bailey, 2002, pp. 122–127; Wilson & Rahman, 2005, pp. 13–16). Sexual fluidity occurs when someone’s sexual orientation by any of the four measures is nonexclusive, changes over time and across situations, or is at variance with each other (Kanazawa, 2017, pp. 1253–1254). © 2019 International Union of Psychological Science FATHER ABSENCE, SOCIOSEXUAL ORIENTATION 235 biologically infertile women, who no longer have the need they are straight) or only to men (if they are gay) (Lippa, or capability to reproduce heterosexually, experience sig- 2006). While this model cannot explain exclusive les- nificantly greater same-sex sexuality than women who bians, Kanazawa (2017, p. 1267) shows that only 0.3% are fertile, while biological infertility is not at all asso- of American women belong in this category. ciated with same-sex sexuality among men (Kanazawa & One developmental factor that has been reliably asso- Larere, 2017). ciated with less restricted sociosexual orientation among Not only does the theory offer an evolutionary expla- both men and women is father absence during early child- nation for female sexual fluidity, it also provides poten- hood (Belsky, 2012; Belsky, Steinberg, & Draper, 1991; tial solutions to many theoretical and empirical puzzles in Draper & Harpending, 1982), although it is more pre- evolutionary psychology and sex research. One such puz- dictive of girls’ developmental trajectories than boys’ zle is the sharp sex difference in the correlation between (Ellis, 2004; James, Ellis, Schlomer, & Garber, 2012). A the number of opposite-sex partners and the number of life-history perspective suggests that girls in early child- same-sex partners. Among men, the correlation is signifi- hood use the presence or absence of their biological father cantly negative, suggesting that there are straight men and in the household either as an indicator of the stabil- gay men as largely separate categories of men. In contrast, ity of pair-bonding and the reliability of male parental among women, the same correlation is significantly pos- investment (Draper & Harpending, 1982) or the degree of itive (Kanazawa, 2017, p. 1259). Women who have sex polygyny in the environment (Kanazawa, 2001). Either with a large number of women simultaneously have sex scenario would suggest to the developing girls that the with an even larger number of men than women who have more adaptive reproductive strategy to pursue in father sex with a small number of (or absolutely no) women do. absence would be to undergo puberty and begin repro- The theory explains this puzzle by proposing that ductive careers earlier. The psychosocial acceleration the- women may not have category-specific (Lippa, Patterson, ory (Belsky et al., 1991) therefore suggests that girls & Marelich, 2010) sexual orientations in the same sense growing up without their biological fathers and in gen- that men do, and instead that women’s sexual orienta- erally more stressful and less supportive environments tion may be a byproduct of their sociosexual orientation, would opt for quantity over quality in their reproductive “differences in individuals’ implicit prerequisites to enter- strategies, whereas girls growing up with their biological ing a sexual relationship” (Gangestad & Simpson, 1990, fathers and in generally less stressful and more supportive p. 70). Women with restricted sociosexual orientation “re- environments would opt for quality over quantity in their quire relatively more time and stronger attachment to, reproductive strategies. commitment to, and closeness with their romantic part- Consistent with the predictions of the psychosocial ners before they are willing to enter a sexual relationship acceleration theory, studies show that girls whose parents with them,” while women with unrestricted sociosexual divorce early in their childhood tend to undergo puberty orientation “require relatively less time with and weaker attachment to their partners before engaging in sex with earlier, start having sex at an earlier age, and have a them” (p. 71). larger number of short-term sexual partners than do If most women are evolutionarily designed to be het- girls whose parents stay married throughout their child- erosexually attracted most of the time (say, 95%) but hood (Ellis, Schlomer, Tilley, & Butler, 2012; Moffitt, experience same-sex attraction in a small fraction of the Caspi, Belsky, & Silva, 1992). Because having more time (say, 5%), then, if a woman has a small number short-term sexual partners (the quantity-over-quality of sexual partners, most or all of them are statistically strategy), as opposed to fewer long-term sexual part- likely to be men. However, as sociosexually less restricted ners (the quality-over-quantity strategy), is a defining women increase the number of sexual partners, many of characteristic of unrestricted sociosexual orientation, the them are statistically likely to be women, while at the psychosocial acceleration theory suggests (and empirical same time having sex with an even larger number of evidence confirms) that girls who experience father men. Women’s unrestricted sociosexual orientation thus absence during early childhood grow up to have less increases the number of same-sex

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