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Archiver > GENEALOGY-DNA > 2010-02 > 1267390860


From: Vincent Vizachero <>
Subject: Re: [DNA] : low variance MRCA dates for P310cladesinItalyandSEEurope
Date: Sun, 28 Feb 2010 16:01:00 -0500
References: <201002282043.o1SKhKLQ024349@mail.rootsweb.com>
In-Reply-To: <201002282043.o1SKhKLQ024349@mail.rootsweb.com>


On Feb 28, 2010, at 3:43 PM, Tim Janzen wrote:

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

The difference in the two estimates will not depend primarily on
sample size, but rather on the structure of the phylogeny in
question. Ken was making this point in a previous post with a
different subject line, I think. If there are long branches in the
phylogeny, no increase in sample size will compensate for that.

> 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.

Fair enough, but this common usage arose in an era during which there
were no good alternatives to intraclade variance. Interclade
estimation, Bayesian methods, and so on allow us to do a better job of
TMRCA estimation than we used to be able to do and so the need to
specify exactly what we are doing is arguably greater now than in the
past.

VV


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