I received a fascinating email from R.H., a professor at a university in Texas. R.H. drew a clever parallel between infanticide in animals and the history of the Spanish Conquistadors in America.
In nature there are numerous examples of infanticide carried out by "step fathers." For example, when a new male joins a chimpanzee troop he will often kill infants. While this horrifies us, it makes evolutionary sense. When a female chimpanzee enters her fertile period she will typically mate with almost all of the males in her troop. This means that the males in the troop have no idea which male fathered which baby. If a male from the troop kills an infant, it could be his own.
But when a new male joins the troop, he can be certain that he's not the father of any of the babies. If he kills the babies it causes their mothers to become fertile again, and he has a higher probability of passing his genes on. So that's exactly what he does.
You see this in humans too. Sadly, human step fathers are roughly fifty times more likely to kill a step child than the natural father of a child – remarkably parallel to the statistics you find in chimpanzees and many other species. We'd like to think we're evolved, that we've moved past our animal instincts, but it just isn't so. You see this pattern throughout nature: a new mate (male or female) is far more likely to kill the "step children" than the natural parent.
So what on Earth does this have to do with Conquistadors? I thought you'd never ask...
Professor R.H. wrote, "The Spanish destroyed many temples, idols, and customs that connected the indigenous population to their ancient religion." That's an understatement. They also killed most of the priests too. And in one of the worst examples of cultural extermination, one Catholic Priest destroyed the entire Mayan written language, thus ensuring that the Mayan religion would be lost and forgotten. (This was one of my most popular blogs ever, running at around 60,000 readers!)
R.H. went on to point out that this is very much like infanticide. Killing infants is a male's way of making room for his own offspring and ensuring that the females aren't using resources raising the babies of other males. The memeplex that we call religion has both defensive memes that help it resist attacks (e.g. the Anti-Rationalism Meme that says faith trumps reason), and offensive memes that help it spread (the Proselytization Meme that tells you to actively spread religion).
And what's the best way for a species to spread? By making room for itself! In the case of a chimpanzee's genes, the male makes room for his offspring by killing babies. In the case of religion, it makes room by killing the "seeds" of competing religions, the priests, and by erasing the temples, icons and written records.
The Conquistadors did exactly that. By destroying the native religion's ability to reproduce itself, they left "fertile ground" in which the Catholic priests could plant their memes.
And it worked. With the priests, temples and memories gone, the Catholic priests who accompanied the Conquistadors had a fertile "ecosphere" – the minds of the remaining indigenous Americans – in which to plant the memes for Christianity.
Which religion dominates Central and South America today? Catholicism. It's a sad but true fact: infanticide and "priesticide" work!