Race-Related IQ

Toby Bradshaw toby at u.washington.edu
Wed Nov 30 16:39:48 EST 1994


In article <gfb1.22.2EDCC8E7 at psu.edu>, Guy F. Barbato <gfb1 at psu.edu> wrote:

>whoa!!!! I think you missed the point, or are you suggesting that we should 
>measure the heritability of IQ so we can breed for (or against) that trait???
>the concept of heritability is only useful as a tool in a selection 
>experiment...

ONLY useful for selection?  Not at all.  Heritability in the broad sense
is a measure of the genetic control of a trait -- the relative contributions
of nature and nurture.  What is done or not done with this information
is secondary to the basic question.

Consider the example of "cancer", a "disease" with similar problems of
definition and environmental variance as "intelligence".  Is it not worth
knowing if "cancer" is largely genetic, largely environmental, or the
result of an interaction between the two?  As it turns out, the etiology
can be largely genetic (e.g., bilateral retinoblastoma), largely
environmental (e.g., infection of a chicken with RSV), or a combination
the two (e.g., unilateral retinoblastoma).  Quantitative and molecular
genetics have joined in distinguishing among these models of "cancer". 
Has all this effort to distinguish among the models been wasted because so
few cures have been found?  Is a woman in a family with familial breast
cancer better off not having the option to know her genotype at one of the
brca loci?  Would we have been better off to treat symptoms of the various
diseases we call "cancer", and skip the basic knowledge?  I would argue
"No" in all three cases. 

To suggest that "intelligence" is somehow above the kind of quantitative
and molecular genetics investigation that has produced a lot of knowledge
(and precious few "cures") about cancer is wrongheaded, IMNSHO.  Neither
definitions of intelligence (or its components) or environmental variance
are insurmountable problems, given human curiosity and ingenuity (maybe
the genome mappers will choose to define "intelligence" as "the ability to
understand genetics"). 

The previous poster's point was that the measurement of heritability
for IQ cannot be meaningful because of the complexity of the underlying
physical structures.  I disagree with this premise, and offered two 
counterexamples.

-Toby Bradshaw
toby at u.washington.edu




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