For a man casual sex with a stranger carried only a small risk—infection, discovery by the wife—and a potentially enormous reward: a cheap addition of an extra child to his genetic legacy. Men who seized such opportunities certainly left behind more descendants than men who did not. Therefore, since we are by definition descended from prolific ancestors rather than barren ones, it is a fair bet that modern men possess a streak of sexual opportunism. Virtually all male mammals and birds do, even those that are mainly monogamous. This is not to say that men are irredeemably promiscuous or that
...more
