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From: lindsay@K.GP.CS.CMU.EDU (Donald Lindsay)
Newsgroups: sci.misc
Subject: Re: Universal Common Female Ancestor
Message-ID: <179@PT.CS.CMU.EDU>
Date: Thu, 15-Oct-87 12:49:13 EDT
Article-I.D.: PT.179
Posted: Thu Oct 15 12:49:13 1987
Date-Received: Sat, 17-Oct-87 08:47:54 EDT
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Several of the postings seemed to be a bit weak on just what it means
to be Eve. Think of it this way:

Mitochronidal family trees are (in the computer science sense) N-ary trees.
Represent each woman as a node, and the number of descendant nodes is the 
number of female children she bears.

Any random mutations are passed down into the subtrees. Other than that,
everybody gets a faithful copy from above.

If "a" is Eve, then suppose that "d" has no daughters. We can erase that
part of the diagram:

            a                    a
           / \                    \
          /   \                    \
         b     c        =>          c
        /     / \                  / \
       /     /   \                /   \
      d      f    g               f    g


...and suddenly, at the moment that "d" dies, "c" becomes Eve !
This may in general happen long after "c" dies. Our current Eve may not
have been Eve for very long: perhaps her sister's mitochrondial DNA was
with us until modern historical times. When Eve was born, someone else
held the title - perhaps her mother, or perhaps her great**N maternal
grandmother. And before that Eve, another, and another, all the way back
to the invention of mitochrondia, where we get into other issues.

-- 
	Don		lindsay@k.gp.cs.cmu.edu    CMU Computer Science