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Archiver > GENEALOGY-DNA > 2010-02 > 1267411543


From: "Tim Janzen" <>
Subject: Re: [DNA] : low variance MRCA dates for P310cladesinItalyandSEEurope
Date: Sun, 28 Feb 2010 18:45:43 -0800
In-Reply-To: <002a01cab8e3$31d8f6f0$5e82af48@Ken1>


Dear Ken,
It is true that the relationship between intraclade coalescence age
estimates and the true TMRCA is rather fuzzy, but generally speaking it
would appear that intraclade coalescence ages frequently underestimate the
true TMRCA. Thus we should strive to avoid stacking the dataset with too
many closely related haplotypes that we know will be skewing our intraclade
coalescence age estimates to be lower than they otherwise would be.
Sincerely,
Tim


-----Original Message-----
From:
[mailto:] On Behalf Of Ken Nordtvedt
Sent: Sunday, February 28, 2010 6:02 PM
To:
Subject: Re: [DNA] : low variance MRCA dates for
P310cladesinItalyandSEEurope


> Another issue is how many haplotypes is optimal for intraclade
> coalescence age estimates. From having done quite a few intraclade
> coalescence age estimates previously I have noted a tendency for
> intraclade
> coalescence age estimates to start declining once you reach 50 or so
> haplotypes.

[[ So what's the problem with declining coalescence age estimates with more
haplotypes? Since the relationship between coalescence age and TMRCA is
rather fuzzy because of not knowing the tree structure, what difference does

it make? Your declining coalescence age is probably approaching the same
for the whole clade tree in any case. What's an "optimal" estimate of
coalescence age? KN]]


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