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Archiver > GENEALOGY-DNA > 2007-02 > 1171460783


From: "Elizabeth O'Donoghue" <>
Subject: [DNA] TMRCA
Date: Wed, 14 Feb 2007 13:46:23 -0000
In-Reply-To: <7.0.1.0.0.20070214000555.1022c450@wells.org>


Orin Wells said in previous messages: 'I just have no confidence in these
MRCA calculations. You are working with mother nature at her random best
with mutations.' and 'I still don't support any computation that is going
to get at the earliest ancestor for MRCA.'

When I look at the various computations of TMRCA that are calculated amidst
the many papers and publications on both small clusters and larger
groups/haplotypes/haplogroups, I can appreciate your position, Orin. As
others have commented as well, the numbers sometimes do not include an SD or
the % of probability within which they are working, and different people
derive different figures from essentially the same database and/or
haplotype. Different researchers and calculators use different mutations
rates to reach an MRCA. There appears, to me at least, to be no common
agreement within the profession of appropriate calculation methods, nor does
there seem to be any mad dash to reach one. Shouldn't this be one of the
fundamental goals of the genetic genealogy community?

I realize the intricacies of different haplogroups and haplotypes and
relative mutation rates amongst them makes this an exceedingly difficult
task. But, with the Genographic project and Sorenson and all the other
databases with increasing amounts of information available, shouldn't
someone take the bull by the horns, so to speak, and make an effort at
adopting a consensus of some sort, at some level, which everyone can use to
compare apples to apples?

I regret I'm in no position to offer expertise in this matter - but I
certainly can offer lots of questions to address. With all of the rest of
you on one side or other of the equation, can anyone see a way forward to at
least begin a process to address the issue? Maybe there is something going
on I am not aware of - if so, please let all of us interested parties know
about it and have hope!

Elizabeth O'Donoghue



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