同性恋基因真的存在吗？

作者：杨超月

同性恋基因真的存在吗？

背景介绍：

同性恋究竟是先天存在、还是后天而来的？这一难题多年来一直困扰着科学家们。而在1993年，美国遗传学家迪恩·哈默一项研究发现了同性恋基因的存在，这一发现随后引起了轰动。那么真的存在同性恋基因吗？

A scientific study has established that there is no “gay gene”

一项科学研究证实，“同性恋基因”并不存在

But biology does in part determine sexual orientation

但是生物学还是在一定程度上决定了性取向

In 1993 A region of the human genome called Xq28 was linked to male homosexuality, and the controversial notion of a “gay gene” was born. Those research findings have not been replicated.

1993年，人们发现人类基因组中一个被称为Xq28的片段与男性同性恋有关，“同性恋基因”这一存在争议的概念由此诞生。这些研究结果后来并未被重复出来。

But it was never going to be that simple: decades of genetic research have shown that almost every human characteristic is a complex interplay of genes and environmental factors. A new study, published in Science this week, confirms that this is the case for human sexuality, too.

但事情从来没有那么简单：人类几十年来对基因的研究表明，人类几乎所有的特征都是基因与环境因素共同作用的结果。本周发表在《科学》杂志上的一项新的研究证实，人类的性取向也是如此。

The study, the largest ever into this difficult topic, was conducted by an international group of scientists working with 23andMe, a personal genomics firm.

一个国际科学家小组与个人基因组公司23andMe就这一难题合作开展了这项迄今为止规模最大的研究。

It used what is called a genome-wide association study (GWAS) on 408 ,995 individuals in the UK Biobank, a British health resource, and 68,527 American 23andMe users—all of whom remained anonymous and consented to the study.

该研究对英国生物银行（一家英国的健康资源库）的408 ,995名个体和美国 23andMe 的68 ,527名用户进行了所谓的全基因组关联研究（GWAS），所有被研究者都是匿名的、并且同意参与这项研究。

A GWAS involves scanning a person’s DNA for tiny variations in the genetic code (simple changes in the As, Ts, Gs or Cs) that correlate with a given trait.

全基因组关联研究是扫描一个人的DNA，以从中找出与特定特征相关的遗传密码的微小变化（只是A、T、G、C碱基的不同）。

The participants were divided on the basis of whether they answered yes or no to the question “Have you ever had sex with someone of the same sex?”—a woolly proxy for sexual orientation, even in the absence of little white lies.

参与者会被问及“你曾经和同性发生过性关系吗?”（即使在不说谎的情况下，这也只是个模糊的性取向指代性问题。）研究者会根据是与否的回答将其分为两组。

The figures the GWAS produced, therefore, relate only to a single act, not to whether someone identifies as gay.

因此，全基因组关联研究得出的数据只与单一行为有关，而无法认定某人是否为同性恋。

The researchers found five genetic markers that were significantly associated with a reported homosexual act by one of the participants in the study.

研究人员发现，有五种基因标志物与参与者报告的同性恋行为显著相关。

None of those markers was on the X or Y sex chromosomes and their total combined effect accounted for less than 1% of the variance. This is because the behaviour is the result of the aggregate effort of hundreds or thousands of genes, whose individual effects are infinitesimally weak.

这些标志物都不在X或Y染色体上，其总的综合效应占总变异的不到1％。原因在于这种行为是成百上千个基因共同作用的结果，而这些基因的单个效应是及其微弱的。

Totting upall the thousands of tested genetic variants accounted for between 8% and 25% of the variation in people’s self-reported homosexual acts. These variants also overlapped with other traits, such as a smoking and an openness to new experiences.