Biodemographic and Physical Correlates of Sexual Orientation in Men

Schwartz, Gene; Kim, Rachael M.; Kolundzija, Alana B; Rieger, Gerulf; Sanders, Alan R.

doi:10.1007/s10508-009-9499-1

Cited by 190 publications

(101 citation statements)

References 71 publications

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“…It should be noted, however, that other investigators have reported a generalized fecundity increase in other members in the pedigrees of male HS probands, independent of the maternal or paternal line (King et al 2005;Schwartz et al 2010), and Rieger et al (2012), based on the dataset by Schwartz et al (2010), found excess fecundity in brothers of male HS. Subsequently, the data by Schwartz et al (2010) were reanalyzed by Camperio Ciani and Pellizzari (2012), highlighting, also in this dataset, a previously unnoticed larger maternal-line female fecundity. Finally, a population dynamics analysis of male HS (see Camperio Ciani et al 2008 and the section Genetic Models for Male HS below), showed a rather singular, previously unconsidered, fecundity increase in paternal aunts of heterosexuals, as compared with homosexuals.…”

Section: Human Homosexualitymentioning

confidence: 80%

Human Homosexuality: A Paradigmatic Arena for Sexually Antagonistic Selection?

Ciani

Battaglia

Zanzotto

2015

Cold Spring Harb Perspect Biol

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Sexual conflict likely plays a crucial role in the origin and maintenance of homosexuality in our species. Although environmental factors are known to affect human homosexual (HS) preference, sibling concordances and population patterns related to HS indicate that genetic components are also influencing this trait in humans. We argue that multilocus, partially Xlinked genetic factors undergoing sexually antagonistic selection that promote maternal female fecundity at the cost of occasional male offspring homosexuality are the best candidates capable of explaining the frequency, familial clustering, and pedigree asymmetries observed in HS male proband families. This establishes male HS as a paradigmatic example of sexual conflict in human biology. HS in females, on the other hand, is currently a more elusive phenomenon from both the empirical and theoretical standpoints because of its fluidity and marked environmental influence. Genetic and epigenetic mechanisms, the latter involving sexually antagonistic components, have been hypothesized for the propagation and maintenance of female HS in the population. However, further data are needed to truly clarify the evolutionary dynamics of this trait. Sexual conflict, the general theme of this collection, has emerged in the last decades as a main research topic in evolutionary biology. Its possible ubiquity and key role have become clear in many phenomena, from speciation to genetic diversity maintenance in populations, sexual phenotypic dimorphism, asymmetric mating and parenting strategies, antagonistic coevolution, and others (Bonduriansky and Chenoweth 2009;Rice et al. 2013; see also Gavrilets 2014). A most interesting example of sexual conflict is given by homosexual (HS) behavior and mate preference in humans, a topic whose societal impact is widely felt at present.Homosexuality is not confined just to our species, but is also occasionally present in numerous animals (Bagemihl 1999;Sommer and Vasey 2006), with permanent, long-term samesex pair bonding having been reported in some birds and ungulates (Bagemihl 1999;Ngun et al. 2011). The presence of not solely sporadic and opportunistic HS behavior has also been observed in nonhuman primates, which suggests our hominid ancestry might also have had HS individuals (Vasey 1995).The main evolutionary questions about HS in our species do not concern occasional HS behavior, which might have, in various con-

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Section: Human Homosexualitymentioning

confidence: 80%

Human Homosexuality: A Paradigmatic Arena for Sexually Antagonistic Selection?

Ciani

Battaglia

Zanzotto

2015

Cold Spring Harb Perspect Biol

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“…In addition, three large studies have reported no sexual orientation-related differences in handedness (Miller et al, 2008;Rahman, Clarke, & Morera, 2009;Schwartz, Kim, Kolundzija, Rieger, & Sanders, 2010). Scholars give the impression that there is consensus for an association between non-right handedness and homosexuality yet these three studies which do not report an association are notable in their sample size and use of continuous measures of handedness.…”

Section: Introductionmentioning

confidence: 99%

Fraternal Birth Order and Extreme Right-Handedness as Predictors of Sexual Orientation and Gender Nonconformity in Men

Kishida

Rahman

2015

Arch Sex Behav

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The present study explored whether there were relationships between number of older brothers, handedness, recalled childhood gender nonconformity (CGN), and sexual orientation in men. We used data from previous British studies conducted in our laboratory (N = 1,011 heterosexual men and 921 gay men). These men had completed measures of demographic variables, number and sex of siblings, CGN, and the Edinburgh Handedness Inventory. The results did not replicate the fraternal birth order effect. However, gay men had fewer "other siblings" than heterosexual men (even after controlling for the stopping-rule and family size). In a sub-sample (425 gay men and 478 heterosexual men) with data available on both sibling sex composition and handedness scores, gay men were found to show a significantly greater likelihood of extreme right-handedness and non-right-handedness compared to heterosexual men. There were no significant effects of sibling sex composition in this sub-sample. In a further sub-sample (N = 487) with data available on sibling sex composition, handedness, and CGN, we found that men with feminine scores on CGN were more extremely right-handed and had fewer other-siblings compared to masculine scoring men. Mediation analysis revealed that handedness was associated with sexual orientation directly and also indirectly through the mediating factor of CGN. We were unable to replicate the fraternal birth order effect in our archived dataset but there was evidence for a relationship among handedness, sexual orientation, and CGN. These data help narrow down the number of possible neurodevelopmental pathways leading to variations in male sexual orientation.

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“…Nevertheless, there is only modest evidence of physical differences between gay/ lesbian and heterosexual individuals suggestive of atypical sexual differentiation (e.g., Schwartz, Kim, Kolundzija, Rieger, & Sanders, 2010). The physical differences that have been found are not found consistently and have weak effect sizes, thus accounting for little of the variance in sexual orientation (Hines, 2011;LeVay, 2010).…”

Section: Introductionmentioning

confidence: 99%

Facial Structure Predicts Sexual Orientation in Both Men and Women

Skorska

Geniole²,

Vrysen³

et al. 2014

Arch Sex Behav

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Biological models have typically framed sexual orientation in terms of effects of variation in fetal androgen signaling on sexual differentiation, although other biological models exist. Despite marked sex differences in facial structure, the relationship between sexual orientation and facial structure is understudied. A total of 52 lesbian women, 134 heterosexual women, 77 gay men, and 127 heterosexual men were recruited at a Canadian campus and various Canadian Pride and sexuality events. We found that facial structure differed depending on sexual orientation; substantial variation in sexual orientation was predicted using facial metrics computed by a facial modelling program from photographs of White faces. At the univariate level, lesbian and heterosexual women differed in 17 facial features (out of 63) and four were unique multivariate predictors in logistic regression. Gay and heterosexual men differed in 11 facial features at the univariate level, of which three were unique multivariate predictors. Some, but not all, of the facial metrics differed between the sexes. Lesbian women had noses that were more turned up (also more turned up in heterosexual men), mouths that were more puckered, smaller foreheads, and marginally more masculine face shapes (also in heterosexual men) than heterosexual women. Gay men had more convex cheeks, shorter noses (also in heterosexual women), and foreheads that were more tilted back relative to heterosexual men. Principal components analysis and discriminant functions analysis generally corroborated these results. The mechanisms underlying variation in craniofacial structure--both related and unrelated to sexual differentiation--may thus be important in understanding the development of sexual orientation.

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Biodemographic and Physical Correlates of Sexual Orientation in Men

Cited by 190 publications

References 71 publications

Human Homosexuality: A Paradigmatic Arena for Sexually Antagonistic Selection?

Human Homosexuality: A Paradigmatic Arena for Sexually Antagonistic Selection?

Fraternal Birth Order and Extreme Right-Handedness as Predictors of Sexual Orientation and Gender Nonconformity in Men

Facial Structure Predicts Sexual Orientation in Both Men and Women

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