IQ; heritability and selection

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------- Forwarded message follows ------

Date: Wed, 19 Oct 1994 10:28:20 EDT
Reply: Human Behavior & Evolution Society <HBES-L@ARIZVM1.ccit.arizona.edu>
From: David.Buss@UM.CC.UMICH.EDU
Subject: IQ; heritability and selection
To: Multiple recipients of list HBES-L <HBES-L@ARIZVM1.ccit.arizona.edu>

David Buss here, responding to Geoffrey Miller.
directional selection.
Assortative mating for things like IQ is known to increase
genetic variance in subsequent generations, and hence increase
heritability estimates. We know that there is assortment
for IQ of about +.45. Given an initial starting point of low
or modest heritability, assortment of this magnitude will
increase heritability estimates over 4 - 5 generations.
Increases are cumulative.
Since it is known that institutions of higher education
place people of similar IQ into proximity, and proximity is
a major determinant of mating, it is not implausible that
heritability estimates for IQ are higher now than they
were 200 years ago. But this would not be due to directional
selection, but rather to an incidental byproduct of
assortative mating.
I'm not arguing that this "must" be the case; just
that it is a plausible alternative explanation.
David Buss

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Juan Carlos Garelli, MD
Attachment Research Center
Juncal 1966, 6B, 1116 Buenos Aires, Argentina
E-mail: gare@psy1.satlink.net Fax: +54-1 812 5432

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