近日，美国加州和挪威相继宣布同性婚姻合法，而科学家对同性恋的研究也取得了重要进展。研究表明，同性恋至少部分是遗传的。虽然同性恋者生育的孩子数要远少于异性恋者，但事实表明，所谓的“同性恋基因”（gay genes）能在人群中幸存下去。新研究对此提出了一个令人感兴趣的观点——这些基因能够增加女性的生育力。研究论文6月18日发表在《公共科学图书馆•综合》（PLoS ONE）上。
虽然科学家至今尚未分离出任何与同性恋直接相关的基因，但是许多研究表明，男同性恋在他们的母系要比在父系拥有更多的男同性恋亲属。这使一些科学家猜测，同性恋基因有可能存在于X染色体上。
2004年，意大利帕多瓦大学进化心理学家Andrea Camperio Ciani领导的研究小组报告，和与异性恋男人有亲戚关系的女人相比，与同性恋男人有亲戚关系的女人生育了更多的孩子。差别相当惊人——比如，男同性恋的母亲平均拥有2.7个孩子，而异性恋男人的母亲平均只拥有2.3个。在姨妈（maternal aunts）身上也具有类似的趋势。
在最新的研究中，Camperio Ciani和同事应用数学模型来寻找可以解释这种现象的理论。研究人员考虑了20多种可能性，比如同性恋基因的数量、这些基因产生的生殖优势有多大、这些基因是位于X染色体还是其它常染色体。
结果发现，能够最佳解释上述数据的模型包含2个同性恋基因，其中至少有一个位于X染色体上。这些基因增加了女性的生育力，同时却降低了男性的生育力，这种现象曾在昆虫和哺乳动物中研究过，称为“性别对抗”（sexual antagonism）。
研究小组表示，这些同性恋基因实际增加的可能是男人和女人对男人的吸引力，而不是如之前研究人员认为的会使同性恋男人更阴柔。这些基因对男性生育力来说不是好事，但它们有益于女性生育，从而能够以虽然低下却稳定的比率在人群中存在下去。
美国国立癌症研究所的行为遗传学家、同性恋基因寻找先锋Dean Hamer认为，这一研究是“一个精致的数学分析。”他表示，此次研究已经提出了一种解决由同性恋造成的达尔文矛盾（Darwinian paradox）的简单方法。他说：“男人体内的‘同性恋基因’就是女人体内的‘超级异性恋基因’”。（科学网 梅进/编译）
（《公共科学图书馆•综合》（PLoS ONE），doi:10.1371/journal.pone.0002282，Andrea Camperio Ciani，Giovanni Zanzotto）
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译文:
NEW RESEARCH："gay genes" promote feminine fertility
Recently, same-sex marriage is recognized legally in California U.S.A and Norway. It is demonstrated that homosexuality owns partly to heredity which is a profound progress scientists have made in the research about it. Although the kids of the same-sex are pretty less than the ones of the heterosexual, the so-called “gay genes” pass down in crowds proved by the facts. An interesting idea occurs in the new research that these genes promote feminine fertility, which has been issued on PLoS ONE in the form of research paper on 18th Jane.
No related gay genes have been separated, but it is illustrated by many researches that gays have more gay relatives in maternality that that in paternality. Some scientists formulate a hypothesis that the gay genes may be a kind of X-linked genes.
A research paper issued by the group led by the Italian evolutionary psychologist Andrea Camperio Ciani from University of Padua in 2004 shows that the women who have gay relatives give birth to more children compared to those with heterosexual relatives. The gap seems extraordinarily great —— for example, the women who have gay relatives have 2.7 kids on average while those with heterosexual relatives have 2.3 per capita. This trend is also found among maternal aunts.
In the latest research, Camperio Ciani and his colleagues take around 20 results, including the member of the gay genes and the advantages in fertility arisen by the genes which are the X-linked genes or others, into consideration applying the mathematical model to seeking the theories to explain the phenomenon.
It is found that the model to explain the foregoing figures contains 2 gay genes at least one of which is X-linked gene. These genes promote feminine fertility while decrease male fertility which is called sexual antagonism once studied in the field of insects and mammals.
The research group says that these gay genes actually perhaps increase the attraction of the men of women to the men instead of the former result that they feminize the gays. These genes, the threats to men, do good to feminine fertility, so they keep the gays survive in the crowds though only occupying a small portion in the people.
Geneticist Dean Hamer from National Cancer Institute, also the pioneer in seeking gay genes believes that this research result is “an accurate mathematical analysis”. He says that this research has formulated a simple solution of the Darwinian paradox caused by the homosexual. He also states that the “gay genes” in men are equal to the “super heterosexual genes” in women.
（PLoS ONE，doi:10.1371/journal.pone.0002282，Andrea Camperio Ciani，Giovanni Zanzotto）