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From: felsenst@entropy.ms.washington.edu (Joe Felsenstein)
Newsgroups: sci.bio
Subject: Re: Universal Common Female Ancestor
Message-ID: <652@entropy.ms.washington.edu>
Date: Tue, 13-Oct-87 10:54:44 EDT
Article-I.D.: entropy.652
Posted: Tue Oct 13 10:54:44 1987
Date-Received: Thu, 15-Oct-87 01:39:10 EDT
References: <894@phoenix.Princeton.EDU> <1248@bsu-cs.UUCP> <11066@beta.UUCP> <317@dg-rtp.UUCP>
Reply-To: uw-beaver!uw-entropy!uw-evolution!joe (Joe Felsenstein)
Organization: Univ of Washington Dept of Genetics, Seattle
Lines: 48
Keywords: mitochondria, Eve, evolution
Summary: many mothers

In article <317@dg-rtp.UUCP> throopw@dg-rtp.UUCP (Wayne A. Throop) writes:
>> dd@beta.UUCP (Dan Davison)
>>> dhesi@bsu-cs.UUCP (Rahul Dhesi)
>>>      All living people (or at least ~99% of them) have a single common
>>>      female ancestor on their purely maternal line....
>> A small correction:  this refers ONLY to mitochondrial DNA, not nuclear DNA,
>> and so for the vast majority of the population says nothing about a single
>> common female ancestor.
>
>How does the fact that mitochondrial DNA was used in this evaluation
>escape the conclusion of a single common female ancestor (SCFA for
>short)?  Mitochondrial DNA comes exclusively from the female parent, and
>if there was a single common original human mitochondrial DNA, it must
>(barring unusually bizarre co-incidences) have come from a single female
>at some point in time.  The evidence supports a single common ancestral
>mitochondrial DNA, hence an SCFA.
>
>> Nor does it imply a population bottleneck 200,000 years ago.
>
>True.  There may have been any number of male ancestors, and the fact
>that only one maternal line survived doesn't mean that it was the only
>maternal line *at* *that* *time*.

Dan Davison is right about the "Eve" publicity having spawned
an amazing amount of misinformation.  Yes, there was a single female who
was the ancestor of all of our mitochondria.  But she was NOT the ancestor of
all of our nuclear genes as well (at least, there is no indication she was).

Your nuclear genes come from both parents, and their nuclear genes from
both their parents and so on back, with parents dropping out randomly
owing to the randomness of mendelian segregation and recombination.  So
ten generations ago you may have had one ancestor up the strictly female
line, but many who were ancestors of your nuclear genes.  

Similarly with "Eve".  The years she lived there probably lived around her
many men AND WOMEN who bore nuclear genes that are represented in the
present human population.

The incredible reaction to the "Eve" story is probably due to its
similarity (accidental) to the biblical story, and to the attractiveness
of notions of an earth-mother-goddess.  Since mitchondria are all
that were involved these are, needless to say, overreactions!

--------------
Joe Felsenstein, Dept. Genetics SK-50, Univ. of Washington, Seattle, WA 98195
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