GENEALOGY-DNA-L Archives

Archiver > GENEALOGY-DNA > 2002-01 > 1010007470


From: "Orin R. Wells" <>
Subject: Re: [DNA] What happened 50,000 years?
Date: Wed, 02 Jan 2002 13:43:38 -0800
References: <OrinWells@wells.org message <4.1.20011229095858.0a2dfcb0@wells.org>
In-Reply-To: <JCHBN.020102.135717.RC0@CUVMB.CC.COLUMBIA.EDU>


At 01:57 PM 1/2/02 -0500, John F. Chandler wrote:
>Orin wrote some things with quotation marks and some things without<<

Those with quotes were from the article and those without were my thoughts.

>> "For a few years there has been broad agreement that the mitochondrial Eve
>> lived around 143,000 years ago, which seems to make nonsense of the 59,000
>> years ago that Nature Genetics reported for the "Y-Adam".
>
>Not at all. People often lose sight of the distinction between "family"
in the sense of a shared surname and "family" in the sense of related
individuals. <<

I believe you missed the issue here. The DNA studies (from the scientists)
is indicating that the existing mtDNA floating around in the current
population pretty much consistently indicates an original souce 143,000
years ago assuming their estimates on time between mutations is accurate.
Whereas the Y-Chromosome DNA pretty consistantly reflects a common ancestry
some 59,000 years ago based on mutations and the same assumed mutation
rates. That is they all should merge at that point in time. It has
nothing to do with family, but with ALL existing populations of
individuals. While your grandfather's Y-Chromosome may no longer be around
because he had only female lines descend, that does not mean his
y-chromosome pattern does not still exist in the population if he had any
brothers, uncles, great uncles etc. who managed to sire a line of males.
If you get enough off spring the odds are still that half of the
descendants (all things being equal) will be males and carry the
originator's y-chromosome. So the question is what happened to eliminate
84,000 years of ancestry for the males? Part of the answer is probably
that it didn't eliminate the ancestry. It just resulted in one branch of
males who dominated totally. All others disappered. All who were left
would be descendants of one person who lived 59,000 years ago based on the
differences being seen today in the y-chromosome DNA. That person lived in
Africa and likely was responsible for some overly agressive tribe that some
time later . Possibly between 50,000 and 45,000 years ago when the
population started to expand into the other areas of the world.

>Reflect on what the finding actually says: all the existing human Y DNA
that has been studied is consistent with a scenario of
gradual mutation from a single source over a period of about 59,000 years.
It does not say that other forms of Y DNA were killed off
somehow.<<

I do not see another logical explanation for the disappearance of 84,000
years of mutation assuming that the scientific estimates are accurate (open
to question). There would have had to have been at least as much diversity
59,000 years ago as we see today and we should see several times that today
but we don't.

>>It does not even say that ALL existing human Y DNA fits the pattern --
there would be a big surprise if more-divergent DNA turned up next week<<

They don't say that, but they haven't found any yet and the researchers
have pretty much tapped every existing population on the planet.

>>It would just mean that the calculated period of mutation would have to
be a bit longer.<<

It would have to be nearly 3 times longer. It may be. If that is so then
the scientists have to go back to the drawing board.

I would think the aborigal population of Australia could hold the answer.
They pretty much know when they hit Australia. A little closer examination
of the mutations present in that population compared to where they are
believed to originate should give them a pretty accurate approximation. I
don't know if anyone has done this.




Orin R. Wells
Wells Family Research Association
P. O. Box 5427
Kent, Washington 98064-5427
<>
http://www.rootsweb.com/~wellsfam/wfrahome.html
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