Department of Psychology, University of Toronto Mississauga, 3359 Mississauga Road North, Mississauga, ON, L5L 1C6, Canada.
Child and Youth Psychiatry, Centre for Addiction and Mental Health, Toronto, ON, Canada.
Arch Sex Behav. 2020 Oct;49(7):2449-2460. doi: 10.1007/s10508-020-01830-8. Epub 2020 Sep 3.
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.
人类同性性吸引被认为是一个进化悖论。这个悖论基于这样一个事实，即同性吸引的个体的直接繁殖率较低，表明影响同性吸引的基因的直接适合度降低。然而，很少有实证研究检验同性性吸引与直接繁殖之间的关系。本研究在一个多样化的泰国样本中（N=1623）检验了异性恋男性和女性、同性恋和双性恋男性以及同性恋和双性恋女性的直接繁殖（即生育的孩子数量），以及泰国独特的性别类别：sao praphet song（即女性化的两性恋第三性别男性）、toms（即男性化的女同性恋第三性别女性）和 dees（即对 toms 有性吸引力的女性化女性）。在男性中，异性恋男性比其他群体更有可能生育孩子，尤其是随着年龄的增长，没有同性恋男性或 sao praphet song 报告有孩子。在女性中，每个考虑的群体都有一定程度的繁殖。平均而言，异性恋和双性恋女性的孩子数量相似，而异性恋女性的孩子数量明显多于女同性恋女性、toms 和 dees。孩子的数量与异性恋女性、双性恋女性、toms 和 dees 的年龄呈显著正相关。随着年龄的增长，异性恋女性与女同性恋女性和 toms 之间平均生育孩子数量的差异变得更加显著。讨论集中在这些发现如何与之前的研究一起，为我们理解与人类同性性相关的进化选择压力提供信息。
