有哥哥的男性更容易成为同性恋

If you’re a guy with an older brother, there’s an increased chance you’re gay.

如果你是一个有哥哥的小伙子，那么你就有可能成为一个同性恋。

Scientists have noticed this pattern in previous research, but now they think they have a biological explanation as to why, and it starts long before birth. The results were published in the journal PNAS on Monday.

科学家已经注意到先前研究中的这种模式，但是现在他们认为他们已经有了一个生理解释关于为什么这会在出生在前就会产生。研究结果已经在周一发布在《美国国家科学院院刊》上了。

The researchers say that if their findings can be replicated, we may know at least one of the biological reasons some men are gay.

研究人员说如果他们的发现能够被复制，那么我们可能至少知道一些男人变成同性恋的生理原因之一。

Many factors may determine someone’s sexual orientation, but in this case, researchers noticed a pattern that may be linked to something that happens in the womb. The phenomenon is related to a protein linked to the Y chromosome (which women do not have) that is important to male brain development.

很多因素可能决定一些人的性取向，但是这种情况下，研究人员注意到了一种可能与发生在子宫里面的某些物质有关的模式。这种现象与连接着对男性大脑发育很重要的 Y染色体（女性没有）的一种蛋白质有关。

Researchers think it’s possible that when a woman gets pregnant with her first boy, this Y-linked protein gets into her bloodstream. The mother’s body recognizes the protein as a foreign substance, and her immune system responds, creating antibodies. If enough of these antibodies build up in the woman’s body and she gets pregnant with another a boy, they can cross the placental barrier and enter the brain of the second male fetus.

研究人员认为当一个女性怀孕第一个男孩的时候，这种和 Y 染色体相连的蛋白质是不可能进入她的血流中的。母体会把这种蛋白质当作一种外来物质，然后她的免疫系统就会做出反应产出抗体。如果这个女性的体内产生足够多的这些抗体，那么当她再次怀男孩的时候，这些抗体就会穿过胎盘进入第二胎男孩的大脑之中。

Earlier research has shown that the more older brothers a boy has, the more of a chance that boy will be attracted to men. A 2006 study showed that with each brother, the chance that a man will be gay goes up by about a third, but the researchers didn’t determine why that was.

早期的研究已经显示，如果一个男孩的哥哥越多，那么他就越有可能吸引男性。2006年的一个研究称：每多一个哥哥，一个男孩变成同性恋的几率就增加了三分之一， 但是研究人员没有找到为什么会是这样的原因。

Bogaert and his co-authors tested a small group of 142 women and 12 men ages 18 to 80 and found a higher concentration of antibodies to the protein, known as NLGN4Y, in blood samples from women than from men. They found the highest concentration of antibodies to the protein in women with gay younger sons who had older brothers, compared with women who had no sons or who had given birth to only heterosexual boys.

博格尔和他的合著者测试了一小群18 岁到80 岁的142 位女性以及12 位男性， 并且发现在女性血液样本中发现一种比男性血液样本之中更高浓度的蛋白质抗体，名为神经元Y连锁蛋白抗体。他们发现 ， 与没有儿子的女性或者已经只生过同性恋男孩的女性相比 ， 生过有哥哥的同性恋男孩的女性体内的蛋白质抗体含量最高。

The study builds on research Bogaert and his co-authors have been exploring for more than 20 years. Since their initial research that noted the trend, other research -- although not all studies -- have detected the phenomenon, even across cultures. One found that a man’s chances of being gay increased even if he was raised apart from his older brother.

以博格尔和他的合著者的研究为基础的课题已经探索了20多年了。 尽管他们最初的研究已经提到过这个趋势，但是别的研究，尽管不是所有的，甚至已经跨越文化， 察觉到这个现象。 其中一个说，即使一个男孩跟他的哥哥分开抚养，他变成同性恋的机会也会增加。