During the heyday of European colonialism, a number of indigenous groups came to the view that, if they had faith, the Europeans’ bullets couldn’t harm them. Needless to say, this meme had disastrous consequences. One group infected with the meme – the Mahdists of Sudan – lost 11,000 men in a single battle to the bullets of Kitchener’s army. This was bad for them obviously, but it was also bad for the meme. In effect, the meme removed itself from the meme pool through its effects on its hosts’ behavior.

It’s often a good idea to adopt the practices and beliefs of the people around you. For one thing, the people around you aren’t dead. If you do what they do – eat what they eat; avoid the dark alleys they avoid – you might continue not being dead as well.

Albert Schweitzer once observed that “When people are free to do as they please, they usually imitate each other.” This was clearly not meant as a compliment. People quote Schweitzer’s statement to thumb their noses at the way we copy each other – which, when you think about it, is rather ironic.

What accounts for psychologists’ kin-blindness – a blindness so profound it would lead to the vaporization of lazy aliens? Part of the answer is that many psychologists, as I’ve already mentioned, have an empty space in their brains where their knowledge of evolution should be. They know little about other animals and little about the nature of the evolutionary process. This impairs their understanding of their own species.

As far as we know, no woman in the history of the species has ever given birth and thought: “Wait a minute! How do I know that this baby is mine and not some other woman’s?” In contrast, if a baby comes out of the body of a woman you slept with nine months ago, that’s not nearly as reliable a clue. As an old saying has it, maternity is a matter of fact, paternity a matter of opinion.

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?