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From:
Subject: Re: [DNA-R1B1C7] The Trinity Ui Neill study
Date: Thu, 17 Jan 2008 18:23:28 EST
In a message dated 1/17/2008 9:11:16 A.M. Central Standard Time,
writes:
Lochlan,
Why would you say:
I'm not sure but I think these figures are assuming a 25 year average per
generation which is probably too low.
In most of recorded history, and probably before that time too, men got
married in their early 20's and women a few years after puberty 16+, they
also lived short lives, so that figure looks conservative to me if
anything?!
Like David and Steve I was thinking of the discussions in the past about the
average length of generations and 30 seemed to be the consensus pick. 30 is
also a figure used by genealogists in the past, including O'Donovan, who
often counted backwards in pedigrees by 30 years a generation in an attempt to
date a person in the pedigree. The technique seemed to work well for him and
I've used it myself.
What really sparked this question for me is the following reference from
the Trinity article:
"The time to the most-recent common
ancestor (TMRCA) of this lineage was estimated
with the r statistic (Morral et al. 1994) in NETWORK,
with use of a mutation rate of 1 per 2,131 years for a
17-marker haplotype (Zhivotovsky et al. 2004)."
They refer to Zhivortovsky et al, 2204, for their mutation rate. I never
could find an actual copy of this paper but I did find the following
reference:
0.00069 per locus per 25 years (Zhivotovsky et al. 2004). ...
The 25 here would seem to be 25 years a generation. If they're using that
figure in their calculations it appeared to me they could be off somewhat in
their TMRCA.
John
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