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  3. Being a man has always been dangerous.There are about 105 males born for every 100 females, but this ratio drops to near Ldance

Being a man has always been dangerous.There are about 105 males born for every 100 females, but this ratio drops to near Ldance

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问题 Being a man has always been dangerous.There are about 105 males born for every 100 females, but this ratio drops to near Ldance at the age of maturity, and among 70- year-olds there are twice as many women as men.But the great universal of male mortality is being changed.Now, boy babies survive almost as well as girls do.This means that, for the first time, there will be an excess of boys in those crucial years when they are searching for a mate.More important, another chance for natural selection has been removed.Fifty years ago, the chance of a baby (particularly a boy baby) surviving depended on its weight.
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答案身为男人，总是有危险。男女出生比率大约为105：100，但到成年时，这种比率下降，几乎达到平衡，在70岁的老年人中，女性比男性多一倍。可是男性死亡率普遍高的现象正在改变。如今的男婴和女婴的存活率一样高。这意味着，男孩到了寻找伴侣的关键年龄，将首次出现男孩过剩现象。更重要的是，自然选择的另一个可能性被排除了。50年前，婴儿(尤其是男婴)存活下来的几率取决于其体重。
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