Department of Psychiatry, University of Toronto, 250 College St., Toronto, ON, M5T 1R8, Canada.
Arch Sex Behav. 2012 Jun;41(3):551-6. doi: 10.1007/s10508-011-9888-0. Epub 2011 Dec 21.
This study tested the balancing selection hypothesis, that is, genes predisposing men to homosexuality escape elimination from the population because the decreased fertility of men with the heritable form of homosexuality is offset by an increased fertility among biological relatives who carry the same genetic variants. The index subjects (probands) were 40,197 firstborn heterosexual men and 4,784 firstborn homosexual men retrieved from six archival data sets, all of which had previously been used in published research. The measure of familial (specifically, parental) fertility was the proband's number of younger siblings. The results directly contradicted the prediction of the balancing selection hypothesis. In four of the six samples, the homosexual probands had significantly fewer younger siblings; in the other two samples, the means were not significantly different. It is possible that mothers who produce a homosexual son at their first delivery include a biologically distinct subpopulation of mothers of homosexual sons.
本研究检验了平衡选择假说，即易患同性恋的基因之所以没有从人群中被淘汰，是因为遗传性同性恋男性的生育能力下降被携带相同遗传变异的生物亲属的生育能力增加所抵消。指数受试者（先证者）为从六个档案数据集中检索到的 40197 名首胎异性恋男性和 4784 名首胎同性恋男性，所有这些数据均曾在已发表的研究中使用过。家族（特别是父母）生育能力的衡量标准是先证者的弟妹数量。研究结果直接与平衡选择假说的预测相矛盾。在六个样本中的四个中，同性恋先证者的弟妹数量明显较少；在另外两个样本中，均值没有显著差异。可能是首次生育同性恋儿子的母亲包含了一个具有生物学差异的同性恋儿子母亲的亚群。
