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Archiver > GENEALOGY-DNA > 2011-01 > 1294155086


From: "Ken Nordtvedt" <>
Subject: Re: [DNA] How old is Y-Chromosome Adam?
Date: Tue, 4 Jan 2011 08:31:29 -0700
References: <201101040808.p0488xgP020485@mail.rootsweb.com><AA814106-788F-475B-9494-D839E21F7AC6@vizachero.com>


[[ And taking into account the explosion in the sigma of the estimates when
restricting to few slowest markers --- which is almost never brought up in
these discussions --- the "accuracy" becomes even more questionable.
Depending on how fast any unmodeled biases grow, their contribution to
inaccuracy could be overwhelmed by the uncertainty of true rate summarized
by the estimate's sigma. The specific rate estimate is not actually what
is delivered by the methods; a probability distribution of rates with a hump
somewhere in the middle, broad or narrow depending on circumstances, is what
is produced. KN ]]



----- Original Message -----
From: "Vincent Vizachero" <>

> It's not clear to me how you would support the conclusion below that
> the most accurate estimate comes from using only 10-20 of the slowest
> markers.
>
> Given our current state of knowledge, I admit it would be hard to
> demonstrate that this is NOT the best approach. But given the very
> real suspicion that the very slowest markers may be overestimating
> TMRCA, an estimate formed ONLY on those markers would - itself- strike
> me as suspicious.
>
> VV
>
>
> On Jan 4, 2011, at 3:08 AM, Tim Janzen wrote:
>
>> I think that
>> it makes the most sense to use a group of the slowest mutating
>> markers from
>> the 67 marker panel, probably no more than 20 and possibly no more
>> than 10.
>
>
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