Seen through a Darwinian lens, men's stronger interest in a partner's looks is initially quite mysterious. In most species, it's the females that care more about looks. Among peacocks, for instance, peahens will only mate with the males with the sexiest tails; males, in contrast, are less shallow and will mate with any female who'll have them. If peacocks had pornography, it would be the females, not the males, that would spend their time staring at images of the other sex, and the males that would complain about being treated as sex objects. And what's true of peacocks is true as well of most animals. In our species, however, it's the other way around. Why?