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From: geoffp@cup.portal.com (Geoffrey Scott Puterbaugh)
Newsgroups: sci.bio,sci.med,sci.psychology
Subject: Re: The persistance of homosexuality in a gene pool
Message-ID: <32366@cup.portal.com>
Date: 2 Aug 90 14:40:58 GMT
References: <1990Jul23.022511.28161@mtcchi.uucp> <11095@netcom.UUCP>  
  <10615@cs.utexas.edu> <1990Jul29.050038.24791@wolves.uucp>
  <32214@cup.portal.com> <476@wicat.UUCP>
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Most of the articles in the twins/homosexuality literature
begin with an "index twin" --  the author(s) discover a gay
man who has a twin, and then proceed to find out whether
his twin is also gay.  This is not true for all of the studies.

The other case -- Hm, this man is hetero, let's check out his
twin! -- seems almost never to happen, except by chance
(as in Heston & Shield's study of a large family with three
sets of male MZ twins.)

Geoff