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Re: African Eve
Richard Hodges (hodges@cnmat.berkeley.edu)
20 May 1994 00:19:29 GMT
In article <1994May9.222923.26055@alw.nih.gov> dmitry pruss,
pruss@helix.nih.gov writes:
>BTW, there was a separate study not long ago - reported in Science - about
>mapping somatic DNA divesity in humans. (This is inherited from both
>parents). There's no clock rate estimate for such things, so the datings
>are relative. Yet the results that emerge are very interesting.
>
>Skipping the details (read Science!), the study detects two past
>bottlenecks in our intraspecies evolution: the earlier one, which excluded
>Ethiopians from the rest of Africans, and more recent one, on the way from
>Ethiopians to *all other* humans outside Africa.
It would appear to me that it would be possible for somatic DNA to give
rise to very different results than maternal, i.e. mitochondrial,DNA. Suppose
males has very
different migration and mating patterns than females. Let's say that
females always stay close to the area they are born. Lets say males have a
persistent pattern of migration from the center of population A to the
center of population B, where they like to mate with the local females. If
eventually population A gets destroyed, then the situation will be this:
the maternal DNA will reflect the history of the females in population B.
The Somatic DNA will reflect mainly the history of population A which might
be quite different; in particular, the last common ancestor could
conceivable be of significantly different age.
An extension of this argument shows that because of possible large scale
sexual exchanges, somatic DNA can potentially be the result of a complex
mixture of populations, which is not the case with maternal DNA. Which one
however do we regard as the real picture? In terms of the percentage of the
genome, somatic DNA is dominant by far. It could easily make the
difference between whether we perceive a monophyletic or a polyphyletic
origin based on DNA analysis of current populations. In any case, it should
give us pause to question the meaningfulness of any such analysis of somatic
DNA.
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