Boys may delay their sisters from becoming women and from having sex, new findings from Australia suggest.

　　The presence of older brothers seemed to delay the onset of menstruation of girls by nearly a year on average, and having younger brothers seemed to postpone the beginning of sexual activity in women by slightly more than a year, scientists found after interviewing 273 Australians.

　　To learn whether they also had an effect on their sisters' reproductive success, researchers investigated 197 women and 76 men. They ranged in age from 18 to 75, and all but 10 - seven of them women - had siblings.

　　“This research helps us to better understand how family dynamics influence development,” said researcher Fritha Milne, a behavioral ecologist at the University of Western Australia.

　　In attempting to explain the delayed starts of menstruation and sexual activity, the researchers ruled out factors such as socioeconomic class. Instead, they conjectured that older brothers may have delayed the physiological maturation of sisters by absorbing more parental resources or by applying psychological stresses. Meanwhile, younger brothers may have delayed girls' behavioral maturation by demanding that their older sisters assume care-taking roles.

　　据美国“趣味科学”网站8月17日报道，男孩的存在可能会推迟自己姐妹变成女人以及发生性关系的时间，澳大利亚科学家的最新研究表明。

　　科学家在调查访问了273名澳大利亚人后发现，哥哥的存在会让女孩子们的月经初潮平均晚来一年，而弟弟的存在则会使女孩初次发生性行为的时间推迟一年以上。

　　为了了解兄弟的存在是否会影响女孩子的生殖情况，研究人员调查访问了197位女性和76位男性。他们年龄在18岁到75岁之间，除了10人没有兄弟姐妹外(10人中有7位是女性)，其他人都不是独生子女。

　　“该项研究有助于我们更好地理解家庭动态如何影响生殖发育，”西澳大学行为生态学家弗利沙-米尔恩说道。

　　为了更好地解释为何女孩初潮以及第一次性关系发生时间会因兄弟的存在而推迟，研究人员排除了某些因素如社会经济等级因素。相反地，他们推测兄长吸取了更多的父亲元素且能够施加心理压力，故而使得女孩子月经初潮推迟。而弟弟希望姐姐承担起照顾自己的责任，从而延迟了女孩们行为的成熟。  
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