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From: elt@astrovax.UUCP
Newsgroups: net.roots,net.women,net.flame,net.misc,net.religion
Subject: A Common Female Ancestor for Everyone
Message-ID: <115@astrovax.UUCP>
Date: Wed, 9-Nov-83 17:54:22 EST
Article-I.D.: astrovax.115
Posted: Wed Nov  9 17:54:22 1983
Date-Received: Fri, 11-Nov-83 02:32:09 EST
Organization: Princeton Univ. Astrophysics
Lines: 33

A rather astonishing discovery was announced by Allan C. Wilson of UC
Berkeley at a meeting at Cold Spring Harbor Laboratory (NY) held in
August '83.  Another group led by Luigi Cavalli-Sforza of Stanford has
verified this result.  Briefly stated, their result is as follows:

All living people (or at least ~99% of them) have a single common female
ancestor on their purely maternal line.  In other words, tracing back to
one's mother's mother's mother's ... mother will bring everyone back to a
single individual woman.  She is estimated to have lived between 50,000 and
500,000 years ago.

This result is based on comparisons of human mitochondrial DNA taken from
very diverse populations all over the world.  Mitochondrial DNA is passed
along solely (i.e., asexually) by females to their offspring.  The mutation
rate for this process is very roughly known, and this together with delicate
measurements of differences between two individuals' mitochondrial DNA, allows
the determination of the interval since they shared a common pure female line
ancestor.  The technique is fairly new and is not yet completely accepted, but
so far no one has suggested any specific reason for doubting its validity.
The most serious uncertainties are associated with the estimate of the time
scale involved but do not alter the basic conclusion of a single common
ancestor.

Explanations for this "fact" are not as difficult as they might at first
appear given reasonable assumptions about population and reproduction
statistics; however, all such explanations imply that the human species
must have once (before!) had a close brush with extinction.

Certainly it is a curious twist on the standard biblical story in which
it is emphasized that people descended from a man through two sons.  It
appears that we actually descended from a woman through two (or more)
daughters.  (Note: Men are simply sterile offspring from the point of
view of mitochondrial DNA.)