The homoerotic behavior that never evolved

The New Genetic Evidence on Same-Gender Sexuality: Implications for Sexual Fluidity and Multiple Forms of Sexual Diversity

In September of 2019, the largest-ever (N = 477,522) genome-wide-association study of same-gender sexuality was published in Science. The primary finding was that multiple genes are significantly associated with ever engaging in same-gender sexual behavior, accounting for between 8-25% of variance in this outcome. Yet an additional finding of this study, which received less attention, has more potential to transform our current understanding of same-gender sexuality: Specifically, the genes associated with ever engaging in same-gender sexual behavior differed from the genes associated with one's relative proportion of same-gender to other-gender behavior. I review recent research on sexual orientation and sexual fluidity to illustrate how these findings speak to longstanding questions regarding distinctions among subtypes of same-gender sexuality (such as mostly-heterosexuality, bisexuality, and exclusive same-gender experience). I conclude by outlining directions for future research on the multiple causes and correlates of same-gender expression.

Psychometric and Faciometric Support for Observable Facial Feminization in Gay Men

Though male homosexuality appears to be evolutionarily paradoxical, phenotypic feminization has been offered as a route for three current models positing a genetic basis for male homosexuality. We tested whether facial feminization is observable in gay men in two studies. In Study 1, using two composite images of gay and of heterosexual men, naive participants (N = 308) rated the "gay" face more highly on stereotypically feminine traits and actual femininity and the "heterosexual" face more highly on stereotypically masculine traits and actual masculinity. In Study 2, faciometrics of 428 Internet images of gay (N = 219) and heterosexual men were analyzed along six sexually dimorphic ratios. The faciometrics of gay men were more feminine, both in gestalt terms and for five of the six individual traits. The studies offer objective support for a more feminized facial phenotype in gay males that is difficult to explain through cultural or behavioral cues.

Scrutinizing Immutability: Research on Sexual Orientation and U.S. Legal Advocacy for Sexual Minorities

We review scientific research and legal authorities to argue that the immutability of sexual orientation should no longer be invoked as a foundation for the rights of individuals with same-sex attractions and relationships (i.e., sexual minorities). On the basis of scientific research as well as U.S. legal rulings regarding lesbian, gay, and bisexual (LGB) rights, we make three claims: First, arguments based on the immutability of sexual orientation are unscientific, given what we now know from longitudinal, population-based studies of naturally occurring changes in the same-sex attractions of some individuals over time. Second, arguments based on the immutability of sexual orientation are unnecessary, in light of U.S. legal decisions in which courts have used grounds other than immutability to protect the rights of sexual minorities. Third, arguments about the immutability of sexual orientation are unjust, because they imply that same-sex attractions are inferior to other-sex attractions, and because they privilege sexual minorities who experience their sexuality as fixed over those who experience their sexuality as fluid. We conclude that the legal rights of individuals with same-sex attractions and relationships should not be framed as if they depend on a certain pattern of scientific findings regarding sexual orientation.

Testing the Affiliation Hypothesis of Homoerotic Motivation in Humans: The Effects of Progesterone and Priming

The frequency of homoerotic behavior among individuals who do not identify as having an exclusively homosexual sexual orientation suggests that such behavior potentially has adaptive value. Here, we define homoerotic behavior as intimate erotic contact between members of the same sex and affiliation as the motivation to make and maintain social bonds. Among both male and female nonhuman primates, affiliation is one of the main drivers of homoerotic behavior. Correspondingly, in humans, both across cultures and across historical periods, homoerotic behavior appears to play a role in promoting social bonds. However, to date, the affiliation explanation of human homoerotic behavior has not been adequately tested experimentally. We developed a measure of homoerotic motivation with a sample of 244 men and women. Next, we found that, in women (n = 92), homoerotic motivation was positively associated with progesterone, a hormone that has been shown to promote affiliative bonding. Lastly, we explored the effects of affiliative contexts on homoerotic motivation in men (n = 59), finding that men in an affiliative priming condition were more likely to endorse engaging in homoerotic behavior compared to those primed with neutral or sexual concepts, and this effect was more pronounced in men with high progesterone. These findings constitute the first experimental support for the affiliation account of the evolution of homoerotic motivation in humans.

Depression: discrete or continuous?

Elucidating the true structure of depression is necessary if we are to advance our understanding and treatment options. Central to the issue of structure is whether depression represents discrete types or occurs on a continuum. Nature almost universally operates on the basis of continuums, whereas human perception favors discrete categories. This reality might be formalized into a 'continuum principle': natural phenomena tend to occur on a continuum, and any instance of hypothesized discreteness requires unassailable proof. Research evidence for discrete types falls far short of this standard, with most evidence supporting a continuum. However, quantitative variation can yield qualitative differences as an emergent property, fostering the appearance of discreteness. Depression as a continuum is best characterized by duration and severity dimensions, with the latter understood in terms of depressive inhibition. In the absence of some degree of cognitive, emotional, social, and physical inhibition, depression should not be diagnosed. Combining the dimensions of duration and severity provides an optimal way to characterize the quantitative and related qualitative aspects of depression and to describe the overall degree of dysfunction. The presence of other symptom types occurs when anxiety, hypomanic/manic, psychotic, and personality continuums interface with the depression continuum.

A Reproductive Threat-Based Model of Evolved Sex Differences in Jealousy

Although heterosexual women and men consistently demonstrate sex differences in jealousy, these differences disappear among lesbians and gay men as well as among heterosexual women and men contemplating same-sex infidelities (infidelities in which the partner and rival are the same sex). Synthesizing these past findings, the present paper offers a reproductive threat-based model of evolved sex differences in jealousy that predicts that the sexes will differ only when the jealous perceivers' reproductive outcomes are differentially at risk. This model is supported by data from a web-based study in which lesbians, gay men, bisexual women and men, and heterosexual women and men responded to a hypothetical infidelity scenario with the sex of the rival randomly determined. After reading the scenario, participants indicated which type of infidelity (sexual versus emotional) would cause greater distress. Consistent with predictions, heterosexual women and men showed a sex difference when contemplating opposite-sex infidelities but not when contemplating same-sex infidelities, whereas lesbians and gay men showed no sex difference regardless of whether the infidelity was opposite-sex or same-sex.

An association between male homosexuality and reproductive success

The existence of homosexuality in humans poses a problem for evolutionary theory. Exclusive male homosexuality has a catastrophic effect on reproduction and yet inherited factors appear to contribute to it. Previous attempts to resolve this conundrum are inconsistent with aspects of evolutionary theory. Additional limitations are as follows. Until recently, accounts of homosexuality have paid little attention to the probable existence of adaptive bisexuality in ancestral populations, from which further variations in sexual orientation may have evolved. Secondly, previous explanations have concentrated on the ancestral environment of two to three million years ago as the determinant of modern sexuality, when more recent influences are likely to have had considerable impact. I argue in favour of a longitudinal rather than cross-sectional model of the ancestral environment. Thirdly, they have often ignored the possibility of variable phenotypic expression, whereby those individuals with a genetic propensity for homosexuality exhibit different and adaptive qualities on most other occasions. It has been demonstrated in previous studies that homosexual men have superior linguistic skills compared to heterosexual men. This may be the result of an adaptive feminising effect on the male brain and apply to many practising heterosexuals. Other adaptations to the recent ancestral environment may include enhanced empathy, fine motor skills and impulse control. By drawing together these contributing factors an evolutionary basis for homosexuality can be demonstrated.

The evolution of homoerotic behavior in humans

This paper presents a theoretical model for the evolution of same-sex sexual behavior, or homoerotic behavior, in humans. Contrary to the traditional study of the topic, the emphasis is on homoerotic behavior itself, irrespective of sexual orientation. It is an inferential model drawn from cross-species evidence, cross-cultural evidence, and current evolutionary theory. It is posited that humans evolved a disposition for homoerotic behavior because it increased same-sex affiliation among peripheralized hominids and indirectly influenced rates of survival and reproductive success. The implications for the conceptualization of same-sex sexual behavior and future research are indicated.