Those Boys Really will be the Death of you, Mom

Mothers who have complained through the centuries that their sons will be the death of them may be rifght --- a study published in the journal <<Science>> shows having boys shortens a woman's life span. Each son takes an average 34 weeks off a woman's life span, evolutionary biologist Samuli Helle and colleagues at the University of Turku found. On the other hand, having daughters adds, but only very slight, to a woman's life span. Helle and Cilleagues looked at birth and marriage records of Sami people from 1640 to 1870."Our results suggest that giving birth to sons had a higher relative long-term survivial cost for mothers than giving birth to and raising daughters." they wrote. There could be biological reasons for this. Studies show boys are physiologically more demanding to produce --- they grow bigger and faster in the womb, and some studies show it takes a woman longer to get pregnant again after having a son than after having a daughter. Testosterone produced by the fetus could suppress the mother's immune system and perhaps make he more susceptible to disease. There could be genetic or social differences among the Sami, who are distint from their Finnish and Swedish neighbor, Helle said. But he dose not think so. " There is no reason believe that this effect would be only visible in Sami people," he siad."Generally, boys get on their mothers' nerves more than girls because they are running around, and girls are move willing to help their mothers."

(Sami:拉普人，Lapp的别称，指居住在北欧拉普兰地区Lapland的人。)

当妈妈的，那些男孩子会害死你的
当妈妈的几个世纪以来一直抱怨她们的儿子们会害死他们也许不无道理---一篇发表在<<科学>>杂志上研究显示,生男孩子会缩短她们的寿命。土尔库(芬兰西南部港市)大学生物进化学家赛谬力．海勒(Samuli Helle)和他的同事研究发现,平均每个男孩子会缩短母亲34周的寿命．另一方面,生女儿却会增加母亲的寿命，只是非常小。海勒和同事们查看了从1640年到1870年拉普人的生育和结婚资料。“我们的结果显示, 母亲们生男孩子所相应付出的生存代价比生育女儿要大”，他们写道。这其中可能有生物原因．研究发现男孩子在生理上对于生产有更多的需求—他们长得更大,更快，一些研究还显示妇女生完男孩子之后再怀孕所需要的时间比生完女孩子后要长。胎儿产生的睾丸激素可以抑止母亲的免疫系统，还有可能使她更容易患病。拉普人同他们的芬兰和瑞典邻居明显不同，也有可能在拉普人中存在遗传或者社会差异，海勒这样说到。但他并不这样认为。“没有理由相信这种影响只存在于拉普人当中”他说“一般情况下，比起女孩子来，男孩子让母亲更耗神，他们总是到处跑，而女孩子总是愿意帮助母亲”。