GENEALOGY-DNA-L Archives
Archiver > GENEALOGY-DNA > 2004-05 > 1083620417
From:
Subject: Re: [DNA] MRCA, Mutations, Statistics, Etc.
Date: Mon, 3 May 2004 17:40:25 -0400 (EDT)
References: <20040430192915.54383.qmail@web50405.mail.yahoo.com>
In-Reply-To: <20040430192915.54383.qmail@web50405.mail.yahoo.com> (messagefrom David Faux on Fri, 30 Apr 2004 12:29:15 -0700 (PDT))
David wrote:
> I'll tell you John, if you agreed with me even once in two years I
> might have ended up with a frontal lobe t.i.a. So I should
> doubtless be thankful that you have continued with an unbroken
> record here.
Contrary to popular belief, discussion groups do not benefit from
posts that say nothing but "I agree". I can assure you all that it
would soon become very tiresome if I felt obliged to point out every
time I agreed with David. I have a policy that I try to follow: if I
can't add something new to a topic or at least use that topic as a
springboard into a new and relevant topic, I don't respond. In the
present case, the thread is in danger of falling into a bout of
bickering, but I am taking this opportunity of urging everyone to
consider adopting a similar policy of reticence.
Getting back to the topic of TMRCA, I do have one further remark. As
David quite rightly points out, the probability distribution is very
broad, so that even an exact 37/37 match does not give 90% confidence
of finding a common ancestor later than 1600. However, this broad
distribution is also very skewed. It is often the case that a
mismatch gives 90% confidence of NOT finding a common ancestor later
than 1600 (or whatever cutoff is of interest). As always in
genealogy, negative information can be as potent as positive
information, but is often much harder to acquire. One of the great
aspects of genetic testing is this ability to provide negative
information. Don't waste it!
John Chandler
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