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Archiver > GENEALOGY-DNA > 2007-02 > 1171490832


From: OrinWells <>
Subject: Re: [DNA] How do you do an estimated Common ancestor
Date: Wed, 14 Feb 2007 14:07:12 -0800
References: <d47.24223dc.33045ffd@aol.com>
In-Reply-To: <d47.24223dc.33045ffd@aol.com>


At 04:52 AM 2/14/2007, wrote:
>that is exactly what MRCA calculations tell you to expect: some
>percentage of brothers will differ

I am going to be sorry I wrote this, I just know I am. But that
never stopped me before. And Ann, I respect you and your
work. Please do not take this personally.

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.

I know I am apparently the only contrarian on this point because so
many of the members of this list seem to think there is some magical
precise science and math involved here. There just isn't It is
totally random. If anyone can show me where this has paid off in
more than one or two equally random cases, I might be willing to say
I am wrong. But it seems to me to be such a waste of time.

>, and some percentage of 10th cousins will be identical, due to the
>random nature of mutations.

From what I have seen it is more than some small percentage.

>MRCA calculations cover a range of probabilities, and they're best
used as a sort of triage: it's
>worthwhile pursuing genealogical evidence

I am not sure what you are suggesting here. It is always worthwhile
pursuing "genealogical evidence" as that is what it is ALL about
after all. But to give me a range of likely generations for a common
ancestor based on a couple of mutations is unlikely to get me to any
valid conclusion and I fail to see how this contributes to the
genealogical pursuit.

For example your own calculator provides this information for 43
markers. I will round for convenience. 0 generation is really 1.

0 mutations = 1 to 21 generations That translates at a conservative
25 years between as 25 to 525 years At a more likely 35 years it gets worse.
1 mutation = 1 to 33 generations 25 to 825 years
2 mutations = 4 to 43 generations 100 years to 1,075

I don't mean to be critical of you personally as I know you have
invested a lot in this. But for a calculation to tell me when I have
two mutations in members of a family that it is likely the most
recent common ancestor lived between 1900 and 925 is a totally
useless bit of information.

No mutations can mean the two are brothers (maybe one or both just
didn't know old Dad), they had a common ancestor who lived in 1483 or
anywhere in between. 2 mutations could have the same implication,
namely that the two brothers maybe didn't know their father to a
common ancestor who lived between 2000 and 925 AD or anywhere between.

Please explain to me exactly how this is going to help me find the
family trees that connect these two to their common ancestor?




Orin R. Wells
Wells Family Research Association
P. O. Box 5427
Kent, Washington 98064-5427
<>
http://www.wells.org
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