Race-Related IQ

Toby Bradshaw toby at u.washington.edu
Mon Dec 5 14:01:24 EST 1994

In article <gfb1.29.2EE32BC6 at psu.edu>, Guy F. Barbato <gfb1 at psu.edu> wrote:
>this was meant to be a post from Dec 4, 1994, to which i accidently "replied" 
>via email....oops.....sorry, toby, i'm still pretty new to this concept!! : )  
>i'm going to try to figure out how to post toby's reply
> guy

No problem.  A [partial] post of my email:

> perhaps you didn't specifically mention narrow or broad sense at all.  Using 

Read the posts.  I specifically said that broad-sense H^2 was what
was interesting.

> vaque terminology in posts, then pleading innocence for not being more 
> specific later smacks of the "oversimplification", if not "special pleading"  
>    : )

Please read what I wrote.


> however, additive variance is *not* irrelevant to broad sense heritability, it 
> is a portion of the total genetic variance.

Additive variance can be zero to 1 without affecting the *ability* to
calaculate broad sense heritability.  If you want to partition the
*genetic* variance, fine.  It's not necessary to do so to calculate
the relative contributions of genetics and environment to a phenotype.


> except for special circumstances (e.g., single gene traits or chromosomal 
> abnormalities) one cannot characterize the genetic contribution to an 
> *individual* phenotype

You might want to bone up on QTL mapping.  Lander and Botstein (1989) Jan
Genetics is a good place to start.  See my upcoming paper in the Feb
Genetics for an extension of this work to trees.  There's no conceptual
reason why a single gene trait represents a "special circumstance",
as has been shown numerous times.

[Prefaced by desirability of a public education tailored to student needs]

> this is the difference between an optimist and pessimist. 

An idealist and a realist.  In theory, theory and practice are
identical.  In practice, they're not.


> >You might want to check into the trisomy 21 literature, which seems
> >to explain individual differences in human intelligence
> >in a very limited sense, and for which negative selection is performed
> >routinely.
> i agree, very limited. and not relevant to the population at large.

Why not?  That's like saying a translocation that causes a defect
in a tumor suppressor is "not relevant".  The key is that intelligence
can have a genetic component.


Re: H^2 vs. h^2

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