Date: Wed, 22 May 1996 15:01:16 -0500 (EST)
Subject: Re: TREE - reply to Terry's of 4-19, part 2 -Reply -Reply


     One critique of mindless adapatationism is what has
been known as "random drift" or the "Sewall Wright Effect."
In short, there are a lot of mutations which have no 
selective significance at all, but because of random migrations
and separations of populations can become differently distributed
in different sub-groups, possibly even leading to speciation.
     A simple example in humans is ABO blood type.  O was the 
original as can be seen by the fact that it is very high in 
"aboriginal" populations including all South American Indians
before intermarriage with Europeans and Africans, and even 
European "aboriginals" such as the Basques and Gaelic-speaking
Irish from Munster.  A was a further back mutation and is quite
widely distributed in peculiar ways (although it is absent in 
Native Americans from Central America south, it is at a 60% rate
among the Nez Perce).  B is the most recent one and clearly occurred
in Central Asia where nearly 40% of the population has it.  One
can measure the degrees of migration from there by its presence.
The only Native Americans to have it pre-Columbianly were the
Eskimos/Inuits.  Among the Basques it is essentially zero and near
zero among the Gaelic-speaking Munster Irish.  It is higher in 
Hungary than in most of Europe, etc.  But there is no selective
significance or advantage to this factor, although there certainly
are such to other aspects of human blood types.
Barkley Rosser
Dept. of Economics
James Madison University
Harrisonburg, VA 22807 USA
tel: 540-568-3212
fax: 540568-3010
e-mail: rosserjb-AT-jmu.edu


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