From: Rafal Smigrodzki (rms2g@virginia.edu)
Date: Wed Oct 02 2002 - 16:26:02 MDT
Damien wrote:
I don't know how the
> mixing process works, but Hans Eysenck, not known for his far-left
> views, was where I learned about `regression to the mean' in IQ. As
> far as I can see, the correlation of child and parent doesn't work to
> make ever brainer and ever stupider kids in each generation via
> assortative mating; if that had happened, you wouldn't just see the
> Flynn effect, you'd be living in a culture where the top IQ had risen
> by a point a generation (or whatever) for the last 10,000 years at
> least. But maybe the effect saturates.
>
### Regression to the mean is a natural by-product of recombination of
recessive traits - the super-smart are so smart because they have the luck
of being homozygous for some IQ-enhancing recessive genes, but for any
single person the exact combination of such genes is likely to be different
than in their super-smart mate. As a result, the offspring will be
heterozygous for many of the traits that made their parents super smart, and
the IQ will be on average lower than the parent IQ.
E.g.
Pat AAbBCCdd x mat aaBBcCDD will produce offspring aAbBcCdD, aABBcCdD,
aAbBCCdD, aABBCCdD. Capitals denote the alleles which if homozygous will
increase IQ. Only one of the filial genotypes will have a combination of two
homozygous high IQ alleles (=same as parents). You do not need a large
number of loci for this effect to be apparent.
The argument for the dysgenic effect of high-IQ emigration on the remaining
population is however independent of the above - if you kill the smartest
25% of the population (or remove them from the group by emigration), the
frequency of high-IQ alleles will be lower. In the example above, try to see
the frequency of F2 (second-generation filial) and subsequent generation
phenotypes from the matings between the first three genotypes (the fourth
moved to Palo Alto). A phenotype will depend on the total number of
homozygous capitals - you will get some phenotypes smarter than the paternal
generation but the overall frequency of high-IQ will be lower with each
generation where you remove the top achiever.
Rafal
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