For the human female cervix, like that of a promiscuous macaque who may breed with ten males or more in rapid succession, actually serves not so much to block sperm, as was previously believed, as to busily filter and assess it, ideally several different types of it from several different males, simultaneously. It evolved not as a simple barrier but to sort the weak and bad and incompatible sperm from the good, suggesting by its very presence that there was a need to do such a thing—i.e., that females were mating multiply. Such a wondrous bit of equipment also partially buffers the female in
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