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Archiver > GENEALOGY-DNA > 2007-02 > 1171507571


From: Vincent Vizachero <>
Subject: Re: [DNA] How do you do an estimated Common ancestor
Date: Wed, 14 Feb 2007 20:46:11 -0600
References: <d47.24223dc.33045ffd@aol.com><7.0.1.0.0.20070214132210.10480e80@wells.org>
In-Reply-To: <7.0.1.0.0.20070214132210.10480e80@wells.org>


On Feb 14, 2007, at 4:07 PM, OrinWells wrote:

> It CAN be expected that sons will differ from their fathers. It had
> to happen somewhere for a mutation to be evident. What is VERY
> unexpected is for two brothers to have haplotypes that not only
> differ from each other but in each case differs from their father in
> a different manner. I only raised this to demonstrate the
> invalidity, in my opinion, of trying to rely on MRCA calculations to
> tell you when a common ancestor lived. To say they lived between 5
> and 15 generations, for example, is totally worthless as far as I
> am concerned.

TMRCA calculators are not designed to "tell you when a common
ancestor lived", as you know, despite the common perception that this
is their function.

TMRCA calculators assign a probability that a common ancestor lived
within a given time frame. Many folks don't like or don't understand
probabilities (or think that they don't), which leads to problems
with perception.

For me, knowing that someone else with my surname (but no other known
genealogical connection) and I have a 97% probability of sharing a
common ancestor within 12 generations is useful information.

Vince

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