From: Ramez Naam (mez@apexnano.com)
Date: Thu Jul 24 2003 - 20:30:35 MDT
I'm interested in feedback on this line of reasoning:
Imagine a trait which has a 0.5 heritability. That is to say that
there's a 0.5 correlation between the trait and one's genes.
Specifically, let's use IQ. Estimates of the genetic component of IQ
vary, but 0.5 is not an unreasonable number.
Now let's imagine you wish to bring into this world children with high
IQs. Using the DNA of someone known to have a high IQ, you create a
number of clones. In this case, let's pick Albert Einstein as the DNA
donor. And let's posit that his IQ was 160.
Alternately, if science has identified every IQ-affecting gene (hah!),
you may start with any human embryos and modify their IQ-related genes
to match Einstein's.
Here are my suppositions about this thought experiment:
1) We do not know the relative contribution of genes and environment
to Einstein's high IQ. In the absence of such specific knowledge, our
best choice is to use the statistical contribution of genes and
environment across the population. The 0.5 heritability in the
population would suggest that half of Einstein's deviation from the
norm in IQ was due to his deviation from typical human genes, and the
other half was due to environmental effects.
2) If we created many children who shared Einstein's IQ-related genes
and raised them in average environments (or a set of environments with
a distribution mirroring the social average), then we'd expect the
average IQ of such children to be 130.
3) The distribution of IQs of these children would form a normal bell
curve centered on 130.
4) The standard deviation of their IQs would be 10 points. (I'm
particularly interested in feedback on this point. Would the standard
deviation remain 10 points given that the genetic contributor to IQ is
fixed?)
5) As an extension of point 3, as many of these children would have
IQs of 100 (dead average) as would have IQs of 160 (Einstein)
Point 5, to me, is a pretty unexpected conclusion. But it seems be an
inevitable consequence of a 0.5 heritability of IQ, and the guess that
Einstein's deviation from the norm in particular was 50% accounted for
by genetics and 50% by environment.
Thoughts?
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