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Archiver > GENEALOGY-DNA > 2007-03 > 1174559553


From: "John McEwan" <>
Subject: Re: [DNA] Cruciani and 2007 TMRCA estimates
Date: Thu, 22 Mar 2007 22:32:33 +1200
In-Reply-To: <BAY105-F35AC8AE6342323C072782DCC6B0@phx.gbl>


Rejoining for a quick reply about Steve and John C's discussion.

I think the interesting aspect of this thread is that the date estimates
of Oppenheimer's book, which are often discussed on this list, and
Cruciani 2007 differ markedly.

Digging under the surface my understanding is Oppenheimer used Forster
et al's (2000) "effective" mutation rates which are 10x lower than
observed father son rates and Cruciani 2007 used an estimate from
Zhivostovsky et al 2006 which is ~3X lower. Ignoring which, if any, is
"better" this single fact alone explains a ~3 fold difference in
estimated ages from the two sources.

It also highlights a key underlying assumption about the whole dating
schema used for Oppenheimer's book. Often we can't see the wood for the
trees, or in this case 534 fact filled pages. It took me some time and
leads from others before I stumbled on this tucked away as a reference
listed on page 440. It is only on reading in some detail the reference
itself that everything fell into place about the age estimates. To quote
from the abstract of Forster et al 2000 "we estimate a mutation rate of
2.6x10-4 mutations/20 years for slowly mutating Y STRs, ~10-fold slower
than the published average pedigree rate".

I hope this helps the casual list reader, who may not have realized that
the estimates really depend less on the information in the paper or the
book and more on the mutation rate used to estimate ages.

Cheers

John McEwan





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