Re: Multi-Regional vs. Replacement, was This might be an even

Clara N. Fitzgerald (cfitzger@s.psych.uiuc.edu)
17 May 1995 16:23:35 GMT

j#d#.moore@canrem.com (J. Moore) writes:

>Lj> basic theories re: the emergence of "modern" humans. Theory 1 seems to
>Lj> be that earlier varieties of hominids (Homo Erectus) radiated out of
>Lj> Africa hundreds of thousands of years ago and sub-populations descended
>Lj> from these "migrants" independently evolved into "modern" humans in a
>Lj> bunch of different geological areas.

> ... [This hypothesis includes] that there did
>not need to be any great migration of a newer population of more modern
>hominids, but that gene flow would occur throughout the then-populated
>world through contact where various populations met. This is easier to

>Lj> Theory 2 suggests that the
>Lj> radiation of earlier hominids occurred just as in Theory 1, but a later
>Lj> radiation of "modern" humans from Africa displaced all of the earlier
>Lj> varieties.

>The MtDNA evidence is often used as evidence for the replacement
>hypothesis, but this is not correct. First, the MtDNA shows only one
>side of the family (it goes from mother to offspring), so it's like
>tracing back your lineage using only your mother's side of the family,
>then her mother's side, and so on. Doing that could, as a hypothetical
>example, show that one is descended from a woman who lived, let's say,
>1000 years ago in what is now Tanzania. But would you be considered to
>be of African descent? The father of that woman's children could have
>been from almost anywhere at that time. Perhaps a visiting Chinese

>So MtDNA does not show the effects of admixture in a lineage; it's like
>tracing back one speck of dust in a single drop of water in a stream.
>It tells you where the speck of dust came from (as far as it can be
>traced) but it doesn't tell you as much as you'd hope about what parts
>of the stream it travelled through.

1) Given large sample sizes, ancestory through the female line should
be about as good an indicator as (paternal) last names - most people
didn't move around very fast.
2) There is mutation in the mtDNA, which allows nested groups to be
arranged - the genetic drift of the African-Chinese line transplanted
to IOndonesia would show different mutations than those remaining in Africa.
I'm not going to touch the problem of rates of mutation - I don't know
enough.
Book on the subject of 'Eve' - The search for Eve , by
Brown, Michael Harold.

>Jim Moore (j#d#.moore@canrem.com)

--

-Clara A. N. Fitzgerald     cfitzger@s.psych.uiuc.edu

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