Department of Biology, Faculty of Mathematics and Natural Sciences, Bogor Agricultural University, Bogor, Indonesia.
Institute of Evolutionary Sciences, CC065 Université de Montpellier, CNRS, IRD, EPHE, Place Eugène Bataillon, 34095, Montpellier Cedex 05, France.
Arch Sex Behav. 2018 Nov;47(8):2455-2465. doi: 10.1007/s10508-018-1202-y. Epub 2018 May 24.
Male homosexual preference (MHP) challenges evolutionary thinking because the preference for male-male relationships is heritable, implies a fertility cost (lower offspring number), and is relatively frequent in some societies (2-6% in Western countries) for a costly trait. It has been proposed that individuals with a MHP counterbalance reproductive costs through the transfer of resources to kin, thereby improving their indirect reproduction through kin's reproductive success. This kin selection hypothesis is not supported in Western countries and Japan, although consistent evidence has been obtained in Samoa. In this study, data from Java (Indonesia) were obtained to assess the avuncular tendencies of men with contrasting sexual orientation to measure possible resource transfer. Consistent with the kin selection hypothesis, males with a homosexual orientation reported an increased willingness to transfer resources toward nephews and nieces and declared having transferred more money to nephews and nieces. We developed a method to quantitatively estimate the contribution of kin selection on inclusive reproduction associated to sexual orientation, taking into account various possible biases. Kin selection reduced the direct reproductive cost of homosexual men by 20%, so suggesting that kin selection alone is insufficient to explain the maintenance of male homosexuality. Other potential factors are discussed, as well as the limitations of the study and the social determinant operating for the expression of increased avuncular tendencies of homosexual men.
男性同性恋偏好（MHP）挑战了进化思维，因为男性间关系的偏好是可遗传的，意味着生育成本（后代数量减少），并且在某些社会中相对频繁（西方国家为 2-6%），这是一种代价高昂的特征。有人提出，具有 MHP 的个体通过将资源转移给亲属来抵消生殖成本，从而通过亲属的生殖成功提高其间接生殖。这种亲属选择假说在西方国家和日本没有得到支持，尽管在萨摩亚已经获得了一致的证据。在这项研究中，从印度尼西亚爪哇岛获得了数据，以评估具有不同性取向的男性的叔伯倾向，以衡量可能的资源转移。与亲属选择假说一致，具有同性恋取向的男性报告说更愿意向侄子和侄女转移资源，并表示已经向侄子和侄女转移了更多的钱。我们开发了一种方法来定量估计与性取向相关的亲属选择对包容性生殖的贡献，同时考虑了各种可能的偏差。亲属选择将同性恋男性的直接生殖成本降低了 20%，这表明仅亲属选择不足以解释男性同性恋的维持。还讨论了其他潜在因素，以及该研究的局限性和影响同性恋男性叔伯倾向增加的社会决定因素。
