Originally Posted by physmom
Kind of going with that... I really wonder about the whole regression to the mean thing. Historically, I can really understand why it happened. Going back 50, 100 years or more people had a much more limited choice on who they married and had kids with (especially considering segregation and the fact that people tended to marry within their economic class and didn't move around as much). That meant that it was more likely that people would have kids with other people all over the IQ spectrum, which means that while two gifted people could produce a kid the previous genes from both sides were still pretty varied when it cames to IQ so that the kid could have a lower IQ.
Now-a-days, it is easier for people to meet and have kids with people of their same intellectual level. Sure, it doesn't always happen, but people tend to gravitate towards someone on their same level or near to it. So it seems regression to the mean would become less prevalent and make genes a better indicator for intelligence.
OK but assortative mating is not the same as selection.
You're assuming that being homozygous for a 'smart allele' is better than being heterozygous for a 'smart allele.' But genetics aren't typically that simple; often something that's good in half-a-dose is not so great in a full dose.
A really well-known example is the sickle-cell gene, which is protective against malaria in a half-dose but creates a nasty disease when present in a full dose.
As a more general point, e.g. mixed-breed dogs are thought to be more clever and even-tempered than true-bred ones, suggesting that a mixed genetic background is a better deal.
WRT intelligence specifically, Simon Baron-Cohen has floated the idea that at least some of the 'autism epidemic' may be due to assortative mating between dorky engineers.http://en.wikipedia.org/wiki/Empathi...emizing_theory
|All that being said... I think this is the wrong question to ask. Maybe it would be better to ask if there are kids that show all the signs of giftedness early on but don't turn out to be at least bright if not gifted. I'm curious does anybody know of a kid that hit all their milestones early (not just one or two but really across the board), didn't sleep well, was highly alert,e tc but didn't turn out to be gifted (or at least bright)? It seems like it would be something interesting to study but I haven't see anything conclusive on it yet...
It definitely happens. Regression of communication/social milestones after relatively appropriate early development is characteristic of Rett's syndrome as well as many autism-spectrum disorders.http://en.wikipedia.org/wiki/Rett_syndrome