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Archiver > GENEALOGY-DNA > 2008-05 > 1210949897


From: "Ken Nordtvedt" <>
Subject: Re: [DNA] age of U152/S28
Date: Fri, 16 May 2008 08:58:17 -0600
References: <5cf61dfb0805160736k50409fe0sbc59d54262837fd9@mail.gmail.com>


By the time you have thousands of samples of haplotypes from Europe, indeed
tens of thousands, if you have missed some "clades" they will be very low
population clades. But one has a scientific obligation to pick one's sample
population for a MRCA estimate as broadly as possible, both in geographical
origins and in extended haplotype motif. This will make the probability
pretty high that one's sample population pruned tree must go to the MRCA you
are seeking; that means you have included some descendants of both his sons.

In any event, you estimate the MRCA for the sample population you have used;
every set of N males has a MRCA. You want to take measures that lead to
that MRCA being as close as possible to the MRCA of the population you are
interested in. In my estimate I took the entire collection of known S28
haplotypes of today according to the avid collector, David.

If you have acquired good sampling of the underlying population of interest
you will find that your TMRCAs don't change much as you redo them with the
additional data which comes in from time to time.

Trying to resurrect the extinct populations that existed but have no
descendants in today's population, no matter how well sampled (including
taking them all) is another question? I suspect there will never be found
enough bones to dig up and test to go very far in this area, except to maybe
discover new clades/haplogroups that did go totally extinct. It only takes
a single case to achieve those kinds of things.

Ken



----- Original Message -----
From: "Michael Walsh" <>
To: <>
Sent: Friday, May 16, 2008 8:36 AM
Subject: [DNA] age of U152/S28


> *I admittedly don't understand MRCA methodologies, but I do have a
> question
> about their validity for determining the age of a haplogroup or subclade.
> It would seem to me that analyzing the haplotypes of extant populations
> may
> be entirely misleading in that there may have been many gene populations
> that have dyed out or have not yet been tested. By nature, as you gather
> more haplotype information from newly "found" groups of a subclade, the
> MRCA
> will push back to earlier times. Am I misunderstanding how MRCA
> methodologies work? or do they account for that the fact that the extant
> branch of the tree you are examining may be only one thin branch?
> --------------------------------------------------------------
> From:* "Jacques Beaugrand"
> <<../mail?view=cm&tf=0&ui=1&to=>>
>
> **...
> On last April 5 2008 I have made an estimate of the age of S28 using the
> available data at the time.
> I am not at all sure of the validity of this result.
>
> Based upon 67 markers and using the Chandler & Little formula with 30
> years
> per generation I found that mutation S28
> would have appeared 3080 years ago, that is 103 generations ago. ........
>
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