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From: emigh@ecsvax.UUCP (Ted Emigh)
Newsgroups: net.bio
Subject: Re: why not incest?
Message-ID: <1847@ecsvax.UUCP>
Date: Wed, 23-Jul-86 10:37:15 EDT
Article-I.D.: ecsvax.1847
Posted: Wed Jul 23 10:37:15 1986
Date-Received: Fri, 25-Jul-86 07:38:48 EDT
References: <2588@mit-eddie.MIT.EDU> <892@ucbcad.BERKELEY.EDU> <1069@ttrdc.UUCP>
Reply-To: emigh@ecsvax.UUCP (Ted Emigh)
Distribution: net
Organization: NC State University
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There is an interesting figure in "Human Genetics", by Dan Hartl (1983, Harper
& Row pg 479).  In the United States, the frequency of first-cousin matings is
about 1%, while in Japan it is about 6%.  In the US the *PERCENTAGE OF
AFFECTED CHILDREN WHOSE PARENTS ARE FIRST COUSINS* (read that again to make
sure you understand it) for Tay-Sachs is about 35%.  In Japan, this percentage
is about 65%, even though the gene frequency of Tay-Sachs is 1/2 that in the
US.  Other genetic diseases show the same relationship.  The message is clear:
While the probability of any single first cousin mating producing an individual
with a genetic disease is quite small, the cost to society is large.

As to the question about how other animals can tolerate high amounts of
inbreeding, it is sort of a chicken and egg question.  Organisms with high
inbreeding tolerate it because they have bred out many of the deleterious
genes.  The human species could "become" a high inbreeding species if we
are willing to pay the price in human suffering (e.g., the survivors of
Pitcairn Island of Mutiny on the Bounty fame).

-- 

Ted H. Emigh     Genetics and Statistics, North Carolina State U, Raleigh  NC
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