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From: "Anatole Klyosov" <>
Subject: Re: [DNA] MRCA Estimates
Date: Sat, 13 Feb 2010 12:22:09 -0500
References: <mailman.4653.1266079356.2099.genealogy-dna@rootsweb.com>


>From: Steven Bird <>
>http://www3.interscience.wiley.com/journal/110433666/abstract?CRETRY=1&SRETRY=0

>31-32 years on average for men. This is pretty consistent with SMGF's
>findings.


Dear Steven,

It is a non-issue regarding TMRCAs calculations.

O.K., I am rather patient with explanations. Let's see. I recently gave an
example:

"If we have, say, 500 of 67-marker haplotypes, and 14 haplotypes among them
are identical to each other (base haplotypes), and the other 486 mutated
haplotypes have (collectively) 1788 mutations from the base, then those 1788
mutations are those that we count".

Therefore, an average number of mutations per marker in this dataset is
1788/500/67 = 0.0534. The average mutation rate constant for the 67-marker
haplotype is 0.00216 mutation per marker per generation, if a generation is
set (sic!) as 25 years. We then have 0.0534/0.00216 = 24.7 generations (it
is of course 25, but for the sake of the example we take this 24.7), that is
24.7x25 = 618 years to a common ancestor. I omit here margins of error, they
are not important in this case.

Now, you or Robert say - no, no, a generation is 32 years per generation.
O.K., no problem. I just have to adjust the mutation rate constant, which
becomes 0.00216x32/25 = 0.00276 mutation per marker per generation.
Therefore we have: 0.0534/0.00276 = 19.3 generations, and 19.3x32 = 618
years to a common ancestor.

As one can see, the TMRCA = 618 years in both cases, regardless 25 or 32
years per generation.

I continue to wonder why such a simple concept meets with such a resistance.

Regards,

Anatole Klyosov



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