Monogamy evolves

Polygamy is pretty popular. Most pre-industrial societies were polygamous in some way, and there are increasing pressures in the west for polygamy to be legalised. After all, it’s surely just a matter of personal freedom of expression. If homosexuality and other forms of sexual expression are legal, then why not polygamy. Polygamy never hurt anyone, right?

Well flat wrong, actually, if the evidence presented by Joe Heinrich, at the University of British Columbia, is anything to go by. Heinrich does some pretty interesting research on human culture and cognition, some of which I’ve covered before on this blog.

But the background to his latest is rather unusual. You see, in Canada they’re holding a court case to determine whether the criminalisation of polygamy is constitutional. And Heinrich has presented some pretty compelling evidence to suggest that if it isn’t, then it darned well should be.

Bottom line is that, in highly stratified societies like most of those in the modern world (and unlike the forager societies that dominated our evolutionary past) polygamy results in surplus males with no prospects of marriage. That in turn causes all sorts of problems. What’s more, polygamy tilts society towards viewing women as property for acquisition, and also decreases investment in children. In the long run, social justice and equality is undermined.

For more on all that, take a look at the write-up in the Vancouver Sun, or read the Heinrich’s brief itself – it’s fascinating stuff!

But what interests me, from the point of view of this blog at least, is what Heinrich infers from these facts. He suggests no less than that the invention of monogamy was the first step in building our modern, democratic society.

Like most sexual innovations, monogamy seems to have been invented by the Ancient Greeks. And, it seems, they devised it as a deliberate ploy to create stronger, more unified city states. Greek culture was highly successful, which lead to monogamy being adopted and then enforced by the Romans. The early Christians incorporated these ideas into their religion as it expanded (there’s no particular stricture against polygamy even in the New Testament).

What we have here is an example of what Heinrich calls ‘cultural group selection’. Those societies that adopt the most effective cultural practices are successful, and they dominate and eventually swallow up the less successful societies around them. And so, around the world nations are gradually adopting monogamy as a social norm (just as Canada is now considering abandoning it!).

According to Heinrich, exactly the same phenomenon gave rise to religion. Although we have all sorts of weird cognitive biases, there is nothing inherent within us that gives rise to religion. But, those societies that were able to most effectively make use of our cognitive biases were the most successful, and the edifice they created is what we call religion.

In other words, God evolved – but in a memetic, not genetic sense, with human society as the host.

But of course, just because a cultural invention was successful in the past, does not mean it will be so when the environment changes. Polygamy works for hunter-gatherer societies, but not for more settled ones – and especially not urban societies. Heinrich quotes Satoshi Kanazawa, who has shown that polygamy in the modern world is linked to increased crime rates.

Kanazawa has also shown that polygamy is linked to IQ. It seems that, even controlling for other factors, nations with higher average IQ are less acceptant of polygamy. He suggests that, the better people are at abstract reasoning, the more likely they are to reject polygamy as unworkable for modern societies.

And Kanazawa has, of course, shown exactly the same thing for religion.

This article by Tom Rees was first published on Epiphenom. It is licensed under Creative Commons.