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Archiver > GENEALOGY-DNA > 2010-02 > 1266426331


From: Sasson Margaliot <>
Subject: Re: [DNA] "counting mutations" versus "GD from the modal"
Date: Wed, 17 Feb 2010 19:05:31 +0200
References: <DD6ED800514C43108F8FA10196306F0D@PC>
In-Reply-To: <DD6ED800514C43108F8FA10196306F0D@PC>


Andrew,

I think I can help with the definition of "Common Ancestor". In everyday
English, a "common ancestor" for a set X of individuals, is someone who
simply is an ancestor common to all members of X.

Unlike everyday English, in this discussion we restrict our attention to
strict patrilinear ancestors only, so Anatole no the only one here who uses
common terms in a special sense, we all do. In a simple sense, common
ancestors for X are the MRCA of X and all his "fathers" all the way up to
Adam.

Anatole is consistently using the term "Common Ancestors" of X in the sense
of exactly "MRCAs of significant, prominent sub-clusters" of X. The precise
protocol of how we should decide which clusters are "significant, prominent"
ones was not presented here, but in practice all the cases are rather clear.

Let me give a specific example: the collection of J1 Cohens. It was fed to
Generations2, returning 2300 years. Then it was examined according to
Anatole's method, and it was discovered that the set has a prominent
sub-set corresponding to a branch which is 1400 years old. The MRCA of
the rest is more like 4000. All numbers are approximate, but the situation
is precisely clear.

You see, all the extra-precision of Generation2 algorithm didn't help at
all.

This is the famous Cohen problem, which is in the center of attention for
more than ten years, the last 15 years, of hobbyists and academics alike -
but it was ONLY possible to receive the right results by subjecting the data
to Anatole's method.

Bottom line: a "Common Ancestor" is the founder of such a sub-cluster that
just has to be calculated separately. By the way, once these "significant,
prominent" sub-clusters are already found, the verification of their
"regularity" is relatively straightforward.

I would rather call Anatole's "Common ancestors" "Founding Fathers". It's
not unusual for one of the "Founding Fathers" of X to turn out to be an
ancestor of all others.

Sasson




On Wed, Feb 17, 2010 <> wrote:

>
> I think we have clarity on the terminology thing. Anatole has some terms
> which caused some confusion, but we have gotten past most of it. In the
> case
> of "counting mutations" and "base haplotype" I at least now know exactly
> what Anaotle means. BUT the problem with "first order" versus "complex" (or
> can we maybe call it simple versus complex) datasets still remains
> unclearly
> defined, whatever words we use.
>
>
>
>


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