RAY BLANCHARD, a researcher at Toronto's Centre for Addiction and Mental Health, was reviewing some data a few years ago when he noticed something odd: gay men seemed to have more older brothers than straight men.
　　几年前，多伦多毒瘾与心理健康中心研究员雷 布朗夏尔在回顾一些数据时注意到一个奇怪的现象——同性恋男子的哥哥似乎比异性恋男子多。

　　Intrigued—and sceptical—he decided to investigate. He recruited 302 gay men and the same number of heterosexual controls and inquired about their families. How many siblings did they have,  what sex, and how had the births been spaced? How old had their parents been when they had had them? Dr Blanchard found that only one detail seemed to predict sexual orientation: the more elder brothers a man had, the more likely he was to be gay. Neither elder sisters nor younger siblings of either sex had any effect, but each additional elder brother increased his chance of being gay by about 33% from the population average of one man in 50.
　　由于对此感到好奇和怀疑，他决定做个调查。他招募了302名同性恋男子和一样多的异性恋男子，并问及一些与家庭有关的问题：有几个兄弟，几个姐妹，前后出生间隔多长时间？出生时父母多大年龄？布朗夏尔博士发现，预示性取向的似乎只有一个细节：哥哥越多，成为同性恋的可能性就越大。姐姐以及弟妹的数量对某人的性取向没有任何影响。一般而言，平均50个男人中就有1人可能成为同性恋，每多一位哥哥，此人成为同性恋的可能性就增加33％左右。