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From: "Ken Nordtvedt" <>
Subject: Re: [DNA] : low variance MRCA dates for P310cladesinItalyandSEEurope
Date: Sun, 28 Feb 2010 14:07:56 -0700
References: <201002282043.o1SKhKLQ024349@mail.rootsweb.com>


----- Original Message -----
From: "Tim Janzen" <>

> Dear Vince and Ken,
>
That said, intraclade estimates
> probably don't underestimate the true TMRCA by a lot as long as the sample
> size is adequate.

[[ Large sample size does not converge the TMRCA of a clade and its
coalescence (self-variance) age. If you used the entire clade population
today you would get two different age estimates because you are estimating
two different properties of the tree. KN ]]



In any case the term TMRCA has been used on this list for
> a very long time and I don't see any reason not to use it as long as we
> know
> what we are referring to.

[[ The problem with just casually using "TMRCA" when what is meant is
self-variance coalescence age estimate is that the latter promotes truly
endless debate on what it is being measured. That is because the
coalescence age depends on the tree structure which is unknown; the TMRCA
does not. All you can argue about with the interpretation of a true TMRCA
estimate from an assumed founding haplotype is the assumed founding
haplotype --- that is before people start arguing about the confidence
interval associated with the estimate.

So again, I recommend abandoning single clade age estimates as much as
possible when you can formulate your question instead of interclade age
estimates. The latter avoid just about all the things to argue about,
although I am sure the disputing will not go away. KN]]



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