I’ve been looking around at some background stuff to assortative mating. As you know from yesterday’s post there’s a linkage between our guru’s (Simon Baron-Cohen that is) thoughts on what is causing the rise in autism and our EQSQ personality tests. As we saw yesterday, assortative mating covers a lot more ground that just the systemizing and empathic traits that our personality tests deal with: it also appears to be part of what is driving the increasing disparity of household incomes in the US.

There’s another well known area where assortative mating has had a huge effect. That’s in the Hindu caste system in places like India and Nepal. The essential idea is that you are born into one of four major groups (which then go on to become some 1,000 separate sub groups) and which group you are part of determines your place in society, in the workplace and, crucially, who you marry. Now one of things that is noted is that the higher castes are quite different genetically from the lower castes. The assumption has always been that the higher castes are descended from the conquerors of the land some 5,000 years ago while the lower castes are the descendants of the conquered. This article explains what they’ve found by looking at the various DNA markers.

It is indeed true that the higher castes are more European (their words, not mine) and the lower more Asian.

Now the only way that such distinctions could be maintained over 5,000 years is exactly by assortative mating: like marrying like, which is exactly what happens within the caste system. I don’t retell this because I approve (or disapprove) of the practice, it’s simply an example to show you how powerful assortative mating can be.

I’ve also seen some other research on the same subject (apologies, not online) which shows that when you break down the genetic markers into those inherited via fathers and those via mothers, those from the lower castes are very rare to find in the higher castes if they come from fathers but much more prevalent if they are maternal. This makes some logical sense: in almost all societies it has been easier for a beautiful woman to marry up than it has been for a man, of whatever talents, to do so.