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out of africa

Don & bashford at scripps.edu
Sat Nov 23 20:30:58 EST 1991

>>>>> On 19 Nov 91 22:50:00 GMT, morphy at cco.caltech.edu (Jones Maxime Murphy) said:

Jones> HXH5 at PSUVM.PSU.EDU writes:

HXH5>Is it not as likely that the greater diversity in Africa just reflects
HXH5>higher effective size of the human population in Africa during the
HXH5>later pleistocene?    It may have nothing to do with time.  And if
HXH5>there is more diversity in Africa, then tree generating algorithms
HXH5>will make trees that look like there are unique African lineages but
HXH5>a lot of others that have both African and non-African representatives.

Jones> At last, a serious and thought-provoking post.

Well, it provoked my thought, but so far I'm drawing a blank as to
how higher "effective size" [What does that mean?] of the human population
in Africa really explains anything.  Doesn't the mtDNA clock run at
the same rate regardless of population?  If so, the difference between
the mtDNA of two individuals should provide a measure of the age of
their youngest common ancestor in maternal lineages.  Even if lower
fertility or higher death rates causes the real complete maternal tree of
a particular population to less branched or more pruned, I don't
see how this effects attempts to reconstruct a tree from a sampling
of mtDNA from contemporary individuals -- a tree which, necessarily,
is severely pruned compared to the real tree since it includes only
those lineages that lead to the sampled individuals.

Don Bashford

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