I haven't blogged about Unnatural Selection much lately, but it has been on my mind. I just came across an old email exchange I had with blog-reader-Dave regarding differential reproduction, and it seems particularly relevant as I've been thinking about family, and children, and grandchildren. Nicole (my oldest daughter) is 27 now, seriously thinking about getting married, and thinking about having kids, and so we're thinking about having grandkids... So.
Here's the exchange, as relevant today as when it took place in May 2003:
An observation on your thesis for Unnatural Selection. I agree in general the factors selecting for intelligence have been on the wane in recent history. However, there may be some countervailing influences going on as well.
One of them, I suspect, is the increased tendency (at least in western societies) for intelligent males hooking up and procreating with equally intelligent females. In the past the primary criteria that intelligent, successful males used in selecting their mates did not include innate intelligence. In fact this attribute was often seen as a liability in potential mates. Fortunately, this "barefoot and pregnant" philosophy has lost much of its legitimacy (again in western society). Of course popular culture (as reflected and amplified by the media) still sends women anti-intelligence messages - in effect saying it's much more important to have high biologic and societal quality than it is intellectual quality.
You're dead right about smart guys meeting smart girls. It really works against regression to the mean. In fact, you could argue the right end of the bell curve is drifting to the right even as the mean drifts to the left.
Unfortunately it doesn't work against Unnatural Selection, in fact quite the opposite.
When smart guys meet smart girls, they generally wait until they're 30+ to have kids, and then when they do they have 2 or so... Meanwhile "not so smart" girls don't get married, they just start having kids in their late teens and dump them on society to take care of, and they might have 5+ to boot. And "not so smart" guys love 'em and leave 'em their chromosomes along the way. So who's really smart? From a genetic standpoint, the "not so smart" girl and guy are much smarter, because their genes will be much better represented in the next generation.
The crux of this problem is that "success" is no longer required for successful reproduction. You could be a prize-winning scientist or a burnt-out junkie, and it doesn't affect your genes' chances of making it to the next generation in any way. In essence the junkie's kids are paid for by the scientist's taxes.
As I look around the world today I think this is happening much faster than I feared when I first began thinking about it at the turn of the century. Not only is there differential reproduction within countries - especially outside the U.S. - but there is differential reproduction between countries. Most of the world's population growth is now taking place in third world countries, supported by first world countries. Scary.
(sorry Dave that it took me so long to blog this, I hope it is still okay :)
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