问题描述：
It could be as simple as the same reason men have nipples - a feature of one sex carries over to
the other because the repercussions of expressing the gene in the sex that doesn't need it are less disastrous than the risk of not expressing it in the sex that needs it.连着上面
the other because the repercussions of expressing the gene in the sex that doesn't need it are less disastrous than the risk of not expressing it in the sex that needs it.连着上面
问题解答：
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