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。
2
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。
3
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.