The development and evolution of male androphilia in Samoan fa'afafine

xvii, 201 leaves : ill. ; 29 cmMale androphilia (i.e., male sexual attraction to males) is an evolutionary paradox. It is unclear how genes for male androphilia persist given that androphilic males have lowered reproduction? Evidence suggests that ancestral androphilic males were transgendered. Hence, I address this paradox by focusing on a group of Samoan transgendered androphilic males (i.e., fa’afafine). Specifically, I show that male androphilia has consistent developmental correlates across Samoan and Western populations, indicating that fa’afafine provide a suitable model for the evolution of male androphilia across populations. In addition, I test hypotheses concerning the evolution of male androphilia. Fa’afafine’s mothers and grandmothers exhibit elevated reproduction. Also, compared to Samoan men and women, fa’afafine exhibit unique kin-investment cognition that would enhance indirect fitness. Elevated reproduction by female kin, and enhanced kin investments may, therefore, contribute to the evolution of male androphilia. Lastly, I outline a developmental model for this unique kin-investment cognition in androphilic males

A Problematic Test of the Kin Selection Hypothesis Among the Urak-Lawoi of Ko Lipe, Thailand: Commentary on Camperio Ciani, Battaglia, and Liotta (2015)

Camperio Ciani et al. argued that the Urak-Lawoi people of Ko Lipe island live in a ‘‘traditional,’’ ‘‘subsistence primitive society’’ reminiscent of the ‘‘ancestral’’ human past and that their socio-cultural situation is ‘‘remarkably similar’’ to Samoa. On this basis, they asserted that the Ko Lipe Urak-Lawoi are an appropriate population for determining the role that kin selection played in the evolution of male androphilia. The purpose of this commentary is to outline some of our concerns with this characterization and with the statistical analyses conducted by Camperio Ciani et al. in their study of the Urak-Lawoi

A Problematic Test of the Kin Selection Hypothesis Among the Urak-Lawoi of Ko Lipe, Thailand: Commentary on Camperio Ciani, Battaglia, and Liotta (2015)

Camperio Ciani et al. argued that the Urak-Lawoi people of Ko Lipe island live in a ‘‘traditional,’’ ‘‘subsistence primitive society’’ reminiscent of the ‘‘ancestral’’ human past and that their socio-cultural situation is ‘‘remarkably similar’’ to Samoa. On this basis, they asserted that the Ko Lipe Urak-Lawoi are an appropriate population for determining the role that kin selection played in the evolution of male androphilia. The purpose of this commentary is to outline some of our concerns with this characterization and with the statistical analyses conducted by Camperio Ciani et al. in their study of the Urak-Lawoi

Elucidating the origins of heterosexual sex differences in mating psychology by examining the behaviour of homosexual men and women

x, 73 leaves ; 28 cm. --Various competing theoretical frameworks have been invoked to explain heterosexual sex differences in mating psychology. Chapter One provides examples of such frameworks, details how considering both heterosexual and homosexual men and women can help identify the most tenable frameworks, and reviews previous research comparing the mating psychology of heterosexual and homosexual men and women. Chapter Two demonstrates the utility of this comparative method by examining the mate retention behaviour of heterosexual and homosexual men and women. Where heterosexual sex differences exist, the mate retention behaviour of homosexual men is largely sex-typical while that of homosexual women is sex-atypical. The significance of these results for explaining heterosexual sex differences in mate retention is discussed. Chapter Three discusses how the data presented and reviewed here might inform our understanding of the psychological mechanisms underlying mating psychology as well as the development of sexual orientation in men and women

A Multi-Modal MRI Analysis of Cortical Structure in Relation to Gender Dysphoria, Sexual Orientation, and Age in Adolescents.

Gender dysphoria (GD) is characterized by distress due to an incongruence between experienced gender and sex assigned at birth. Sex-differentiated brain regions are hypothesized to reflect the experienced gender in GD and may play a role in sexual orientation development. Magnetic resonance brain images were acquired from 16 GD adolescents assigned female at birth (AFAB) not receiving hormone therapy, 17 cisgender girls, and 14 cisgender boys (ages 12-17 years) to examine three morphological and microstructural gray matter features in 76 brain regions: surface area (SA), cortical thickness (CT), and T1 relaxation time. Sexual orientation was represented by degree of androphilia-gynephilia and sexual attraction strength. Multivariate analyses found that cisgender boys had larger SA than cisgender girls and GD AFAB. Shorter T1, reflecting denser, macromolecule-rich tissue, correlated with older age and stronger gynephilia in cisgender boys and GD AFAB, and with stronger attractions in cisgender boys. Thus, cortical morphometry (mainly SA) was related to sex assigned at birth, but not experienced gender. Effects of experienced gender were found as similarities in correlation patterns in GD AFAB and cisgender boys in age and sexual orientation (mainly T1), indicating the need to consider developmental trajectories and sexual orientation in brain studies of GD

Offspring Production among the Extended Relatives of Samoan Men and Fa'afafine

Androphilia refers to sexual attraction to adult males, whereas gynephilia refers to sexual attraction to adult females. Male androphilia is an evolutionary paradox. Its development is at least partially influenced by genetic factors, yet male androphiles exhibit lower reproductive output, thus raising the question of how genetic factors underlying its development persist. The sexual antagonism hypothesis posits that the fitness costs associated with genetic factors underlying male androphilia are offset because these same factors lead to elevated reproduction on the part of the female relatives of androphilic males. Western samples drawn from low fertility populations have yielded inconsistent results when testing this hypothesis. Some studies documented elevated reproduction among the matrilineal female kin of androphilic males, whereas others found such effects in the paternal line. Samoa is a high-fertility population in which individuals reproduce closer to their maximum capacities. This study compared the reproductive output of the paternal and maternal line grandmothers, aunts, and uncles of 86 Samoan androphilic males, known locally as fa'afafine, and 86 Samoan gynephilic males. Reproductive output was elevated in the paternal and maternal line grandmothers, but not aunts or uncles, of fa'afafine. These findings are consistent with the sexual antagonism hypothesis and suggest that male androphilia is associated with elevated reproduction among extended relatives in both the maternal and paternal line. Discussion focuses on how this study, in conjunction with the broader literature, informs various models for the evolution of male androphilia via elevated reproduction on the part of female kin

On the importance of stimulus selection in replicating studies of within-sex variation in mental rotation test performance

This is an accepted manuscript published by Elsevier.Understanding of visuospatial cognition has been informed by studying within-sex variation. Peragine et al. help disentangle possible explanatory variables that are confounded in between-sex comparisons (e.g., sex hormones, gender socialization). In their sample of individuals assigned female at birth (AFAB), hormonal status helped account for group differences in visuospatial performance.Natural Sciences and Engineering Research Council of Canada Discovery Grant awarded to DPV (RGPIN-2016-06446)

Direct Reproduction and Sexual Orientation and Gender Diversity in Thailand

This is an accepted manuscript published by Springer.Human same-sex sexual attraction is considered to be an evolutionary paradox. This paradox rests on same-sex attracted individuals having lowered direct reproduction, indicating reduced direct fitness of genes that influence same-sex attraction. Yet, relatively few empirical studies have examined the relation between same-sex sexual attraction and direct reproduction. The present study examined direct reproduction (i.e., number of children produced) in a diverse Thai sample (N = 1623) of heterosexual men and women, gay and bisexual men, and lesbian and bisexual women, as well as unique Thai gender categories: sao praphet song (i.e., feminine androphilic third-gender males), toms (i.e., masculine gynephilic third-gender females), and dees (i.e., feminine females who are sexually attracted to toms). In males, heterosexual men were more likely to have produced children than other groups, especially as they aged, and none of the gay men or sao praphet song reported having children. In females, there was some degree of reproduction in each of the groups considered. On average, heterosexual and bisexual women had similar numbers of children, whereas heterosexual women had significantly more children than lesbian women, toms, and dees. Number of children was significantly positively associated with age among heterosexual women, bisexual women, toms, and dees. With age, the discrepancies in average number of children produced between heterosexual women and each of lesbian women and toms became significantly more pronounced. Discussion focuses on how these findings, in conjunction with those of prior studies, inform our understanding of evolutionary selection pressures related to human same-sex sexuality.Natural Sciences and Engineering Research Council of Canada Discovery Grant awarded to DPV (RGPIN-2016-06446)

Birth order and sibling sex ratio of children and adolescents referred to a gender identity service.

In adult male samples, homosexuality is associated with a preponderance of older brothers (i.e., the fraternal birth order effect). In several studies comparing gender dysphoric youth, who are likely to be homosexual in adulthood, to clinical or non-clinical control groups, the findings have been consistent with the fraternal birth order effect in males; however, less is known about unique sibship characteristics of gender dysphoric females. The current study investigated birth order and sibling sex ratio in a large sample of children and adolescents referred to the same Gender Identity Service (N = 768). Probands were classified as heterosexual males, homosexual males, or homosexual females based on clinical diagnostic information. Groups differed significantly in age and sibship size, and homosexual females were significantly more likely to be only children. Subsequent analyses controlled for age and for sibship size. Compared to heterosexual males, homosexual males had a significant preponderance of older brothers and homosexual females had a significant preponderance of older sisters. Similarly, the older sibling sex ratio of homosexual males showed a significant excess of brothers whereas that of homosexual females showed a significant excess of sisters. Like previous studies of gender dysphoric youth and adults, these findings were consistent with the fraternal birth order effect. In addition, the greater frequency of only children and elevated numbers of older sisters among the homosexual female group adds to a small literature on sibship characteristics of potential relevance to the development of gender identity and sexual orientation in females