The human head louse, for instance, evolved from the chimpanzee louse when the ancestors of humans and chimps split apart some five million years ago.
例如，人头虱是500万年前当人类祖先与黑猩猩分化时从黑猩猩身上的虱子进化来的。
Contagious: a human head louse clings to a strand of hair.
感染力：附着在一根头发上的人类头虱。
One of the more embarrassing mysteries of human evolution is that people are host to no fewer than three kinds of louse while most species have just one.
人类进化的一个最令人不堪的秘密就是人身上至少长着三种虱子，而大多其他物种只长着一种。
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