Human social stratification and hypergyny: toward an understanding of male homosexual preference

Fertility of Czech Gay and Straight Men, Women, and Their Relatives: Testing the Sexually Antagonistic Gene Hypothesis

One proposal for the persistence of homosexuality in the human population is the sexually antagonistic gene hypothesis, which suggests that the lower fertility of homosexual individuals, especially men, may be compensated by higher fertility of their relatives of the opposite sex. To test this hypothesis, we have collected data from 7,312 heterosexual men, 459 gay men, 3,352 heterosexual women, and 79 lesbian women mainly from Czechia. In an online survey, participants answered questions regarding their own as well as their parents' and grandparents' fertility. For men, we obtained no significant results except for higher fertility of gay men's paternal grandmothers, but the magnitude of this effect was very small. For the female sample, we recorded lower fertility of lesbian women's mothers and fathers. In line with our expectations, both gay men and lesbian women had lower fertility rates than their heterosexual counterparts. Our results are consistent with recent studies which likewise do not support the sexually antagonistic gene hypothesis.

Religious celibacy brings inclusive fitness benefits

The influence of inclusive fitness interests on the evolution of human institutions remains unclear. Religious celibacy constitutes an especially puzzling institution, often deemed maladaptive. Here, we present sociodemographic data from an agropastoralist Buddhist population in western China, where parents sometimes sent a son to the monastery. We find that men with a monk brother father more children, and grandparents with a monk son have more grandchildren, suggesting that the practice is adaptive. We develop a model of celibacy to elucidate the inclusive fitness costs and benefits associated with this behaviour. We show that a minority of sons being celibate can be favoured if this increases their brothers' reproductive success, but only if the decision is under parental, rather than individual, control. These conditions apply to monks in our study site. Inclusive fitness considerations appear to play a key role in shaping parental preferences to adopt this cultural practice.

Facial Attractiveness of the Sisters of Istmo Zapotec Men and Muxes: Implications for the Evolution of Male Androphilia

Research shows that the female relatives of androphilic (i.e., sexually attracted to adult males) males have more children than the female relatives of gynephilic (i.e., sexually attracted to adult females) males. The mechanisms by which this occurs are unclear. The hypergyny hypothesis suggests that the female relatives of androphilic males have elevated attractiveness which allows them to obtain male partners with higher socioeconomic status, which in turn, provide them with more resources to produce and sustain multiple offspring. We tested whether the female kin of male androphiles are characterized by elevated attractiveness compared to the female kin of male gynephiles. The research was conducted among the Istmo Zapotec from Oaxaca, Mexico, where androphilic males are recognized as a third gender, muxes. We recruited 115 gynephilic men who rated the facial attractiveness of 27 women with at least one muxe sibling and 27 women with only gynephilic male siblings (i.e., control sisters). The results showed that gynephilic men found the faces of control sisters more attractive than the faces of muxe sisters. This finding is inconsistent with the hypergyny hypothesis and suggests that elevated facial attractiveness is not the mechanism by which the female relatives of androphilic males achieve elevated reproduction.

Facial Attractiveness of Sisters of Thai Gay Men and Sao Praphet Song

Androphilia refers to sexual attraction toward adult males. Androphilic males' female genetic relatives might offset the fitness cost of androphilia by having elevated numbers of offspring. Increased attractiveness relative to other women may enable these females to marry up the social hierarchy, providing greater access to resources to support more offspring. In Thailand, there is a marked status hierarchy and male androphiles are highly visible - identifying as gay men or as a third gender known as sao praphet song. Thus, a field experiment was conducted in which 208 heterosexual men rated the facial attractiveness of 25 sisters of Thai gay men or sao praphet song and 25 comparison women with no known same-sex attracted relatives. Contrary to the prediction, the comparison group was rated as more attractive than the sisters, casting doubt on hypotheses that posit greater attractiveness of female relatives of male androphiles as a proximate mechanism facilitating the evolutionary maintenance of genes influencing male androphilia. Also, men from rural areas rated the women, regardless of group, as more attractive than men from urban areas, consistent with some prior studies showing rural-urban differences in perceptions of attractiveness.

A Worldwide Internet Study Based on Implicit Association Test Revealed a Higher Prevalence of Adult Males' Androphilia than Ever Reported Before

BACKGROUND

Social constrictions or the lack of a clear awareness about one's sexual orientation may influence the ability of individuals to explicitly declare their sexual preferences. Thus, the actual prevalence of males' sexual attraction toward adult males, which is estimated by studies relying only on explicit questionnaires, may be biased. Conversely, the implicit measurement of androphilia may be a promising method to obtain more reliable data.

AIM

In the present work, explicit and implicit methods have been used to investigate the rates of explicit nonheterosexuality and implicit androphilia in a large sample of adult males from all around the world. For implicit androphilia, a rate consistent across the continents and close to that predicted by recent genetic models (about 15%) was expected. In contrast, for self-declared homosexuality, a lower and more variable rate was expected.

METHODS

A sample of 1,050 participants was recruited through an online platform. All participants completed a short biographical questionnaire, an Autobiographical-Implicit Association Test, the Sexual Preference-Implicit Association Test, and an explicit measure of sexual orientation. The answers to these measures were used to explore explicit sexual orientation and implicit androphilia across six main geographical areas (Middle East and Africa, South America, North America, Asia, Europe, and Oceania).

OUTCOMES

The main outcome measures were the D score at the Sexual Preference-Implicit Association Test and the scores at the explicit measure of sexual orientation.

RESULTS

The rate of nonheterosexuality, which can be found using explicit measures, is rather low, variable (from 6.3% to 11.4%), and influenced by cultural factors. In contrast, the prevalence of androphilia resulting from implicit methods is higher and consistent across geographical areas (from 14.4% to 17.6%).

CLINICAL IMPLICATIONS

Studying the diffusion of adult males' androphilia may be useful to better understand sexual behaviors and preferences and to develop effective health promotion programs among males who have sex with males.

STRENGTHS & LIMITATIONS

The large and cross-cultural sample and the use of both implicit and explicit measures allowed for obtaining a detailed picture of adult males' sexual orientation and androphilia. The main limitations were the Web-based characteristics of the protocol and the lack of an investigation of actual sexual behaviors.

CONCLUSION

Compared with the explicit measurement of nonheterosexuality, the implicit measurement of sexual preferences showed a prevalence of androphilia among adult males that is higher, more stable across continents, and more consistent with the predictions of recent genetic models. Colledani D,A. Camperio Ciani Worldwide Internet Study Based on Implicit Association Test Revealed a Higher Prevalence of Adult Males' Androphilia than Ever Reported Before. J Sex Med 2021;18:4-16.

Male Homosexual Preference: Femininity and the Older Brother Effect in Indonesia

Male homosexual preference (MHP) is an evolutionary enigma because it is partially heritable and imposes a fertility cost. In occidental societies, homosexual men are feminized at various levels and they have more older brothers than heterosexual men. To evaluate whether femininity and the fraternal birth order (FBO) effect are universal features of MHP or not, we collected original data from homosexual men, heterosexual men, and heterosexual women from Java (Indonesia). Facial photographs were used to test whether homosexual faces are feminized when compared with heterosexual ones. We found that faces manipulated to resemble the average face of homosexual men are perceived as facially feminized, suggesting that homosexual men are facially feminized compared to heterosexual men, although a higher facial femininity was not captured by morphological analyses. Then, family data were used to detect differences in siblings' composition between homosexuals and heterosexuals. Homosexual men displayed a higher number of older brothers than heterosexual men, even when sibship size was controlled for, suggesting that the FBO effect exists in Indonesian populations. Independent of sexual orientation, men with older brothers seem more feminized than those without older brothers, consistent with the immune origin of the FBO effect. In conclusion, MHP in Indonesia is partially feminized and they have more older brothers. Such features are also associated with MHP in other cultural contexts, suggesting a cross-cultural effect of men homosexual preference. An evolutionary explanation is available for the feminizing effect, although the FBO effect remains unexplained even if proximal mechanisms start to be identified.

Is Male Androphilia a Context-Dependent Cross-Cultural Universal?

The cross-cultural ethnographic literature has traditionally used the label male "homosexuality" to describe sexual relationships between biological males without considering whether or not the concept encompasses primary sexual attraction to adult males. Although male androphilia seems to be found in all national populations, its universal existence in tribal populations has been questioned. Our goal is to review previous cross-cultural classifications and surveys of male same sex behavior to present a system that does justice to its varied expressions, especially as it is informed by contemporary sexuality research. Previous comparative research does not effectively distinguish male same sex behavior from male androphilia. Using the standard cross-cultural sample (SCCS) as a sampling frame and the ethnographic sources in the human relations area files and elsewhere, we present distributional data on various forms of male same sex behavior. The SCCS is useful because it is designed to be representative of all historically known social formations and the sample is designed to reduce similarities as a consequence of common descent or historical origin as well as reduce the probability of diffusion of sociocultural practices from one culture to another. Our results show that male same sex behavior as well as male androphilia is much more common than previously estimated in the SCCS. With our findings, we make an argument that male androphilia is a context-dependent cross-cultural universal.

What can cross-cultural correlations teach us about human nature?

Many recent evolutionary psychology and human behavioral ecology studies have tested hypotheses by examining correlations between variables measured at a group level (e.g., state, country, continent). In such analyses, variables collected for each aggregation are often taken to be representative of the individuals present within them, and relationships between such variables are presumed to reflect individual-level processes. There are multiple reasons to exercise caution when doing so, including: (1) the ecological fallacy, whereby relationships observed at the aggregate level do not accurately represent individual-level processes; (2) non-independence of data points, which violates assumptions of the inferential techniques used in null hypothesis testing; and (3) cross-cultural non-equivalence of measurement (differences in construct validity between groups). We provide examples of how each of these gives rise to problems in the context of testing evolutionary hypotheses about human behavior, and we offer some suggestions for future research.

Male Homosexual Preference: Where, When, Why?

Male homosexual preference (MHP) has long been of interest to scholars studying the evolution of human sexuality. Indeed, MHP is partially heritable, induces a reproductive cost and is common. MHP has thus been considered a Darwinian paradox. Several questions arise when MHP is considered in an evolutionary context. At what point did MHP appear in the human evolutionary history? Is MHP present in all human groups? How has MHP evolved, given that MHP is a reproductively costly trait? These questions were addressed here, using data from the anthropological and archaeological literature. Our detailed analysis of the available data challenges the common view of MHP being a "virtually universal" trait present in humans since prehistory. The conditions under which it is possible to affirm that MHP was present in past societies are discussed. Furthermore, using anthropological reports, the presence or absence of MHP was documented for 107 societies, allowing us to conclude that evidence of the absence of MHP is available for some societies. A recent evolutionary hypothesis has argued that social stratification together with hypergyny (the hypergyny hypothesis) are necessary conditions for the evolution of MHP. Here, the link between the level of stratification and the probability of observing MHP was tested using an unprecedented large dataset. Furthermore, the test was performed for the first time by controlling for the phylogenetic non-independence between societies. A positive relationship was observed between the level of social stratification and the probability of observing MHP, supporting the hypergyny hypothesis.