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Archiver > GENEALOGY-DNA > 2007-03 > 1174588176


From: "Elizabeth O'Donoghue" <>
Subject: Re: [DNA] Cruciani and 2007 TMRCA estimates
Date: Thu, 22 Mar 2007 18:29:36 -0000
In-Reply-To: <000001c76c6d$6a406a70$4101a8c0@BigMem2>


John McEwan explained that:

1. 'Oppenheimer used Forster et al's (2000) "effective" mutation rates'

2. 'Cruciani used an estimate from Zhivostovsky et al (2006)'

3. 'observed father son rates' are 10x and 3x higher, respectively

And there are other rates such as John Chandler's as well.

I first want to thank John and others who have responded to my earlier
inquiries about TMRCA, but I am still searching for some semblance of order
and continuity to the whole subject. While #3 seems to be based on 'real'
statistics, I wonder how many father-son comparisons were made to arrive at
those rates. I wonder how Forster and Zhivostovsky arrived at their rates.
I wonder what years/generations was used and what SD applies to any of these
rates. As well, in principle, I don't see why there should be any
difference between comparing short or long distances when deciding what
rates to use - do the odds increase when you look longer?

Partly because my DNA project is with Family Tree, and partly because I
suspect a good number of other group administrators who follow this list
also are based there, I must continue to wonder why so many consider FT's
mutation rates as too short, since the database they have available to them
in determining the rates they use is probably much larger than other
studies - maybe I'm wrong. I don't know why they don't publish their
results - I'm asked about it a number of times.

It appears most Group Admin's - at FT anyway - use the FT TiP calculator
when compiling results for their projects. What credence can we provide in
reporting to our participants the results we are producing, when the larger
community suggests their calculations are inadequate? A number of projects
I have reviewed (mainly Irish/Scottish, I admit) are seeking answers to the
origin myths of their ancestors - while they are usually still A.D., we may
be going back 2000+ years. I know that Family Tree has less confidence in
they calculations past about 600 years (24 generations at 25 years), so what
do we do?

Dean McGee's Y-Utility does not offer a TMRCA for the whole dataset input,
does it? What options do we have in that regard? What minimum number of
records should you have for comparison to expect an MRCA to have validity?
I did receive an excel spreadsheet with formulas using STDEV and
Zhivotovsky's rates. If there is a standard deviation to consider with his
rates, what is it?

I'm still wishing you'd all come to Ireland for a conference and agree to
SOMETHING for us all... :-)))))

I value your expertise and appreciate your help.

Elizabeth




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