GENEALOGY-DNA-L ArchivesArchiver > GENEALOGY-DNA > 2010-02 > 1266205134
From: "Alister John Marsh" <>
Subject: Re: [DNA] TMRCA assessments
Date: Mon, 15 Feb 2010 16:38:54 +1300
I personally think we are making progress!
I now have sufficient understanding of your system to personally have
increased concerns about it's reliability.
You have reached a point where there are questions about your system which
you do not want to discuss.
If your system typically arbitrarily treats a "modal" haplotype as an
"ancestral" haplotype for the basis of mutation counting, then it seems to
me your system has a significant flaw.
Your arbitrary decision in this regard could change the "total mutation
count" by a factor of 2 in the real life example I gave you a few days ago.
Whilst "a factor of 2" may not seem of any consequence to you it seems a lot
to my unmathematically trained mind. At least it seems a lot to have
swinging on an arbitrary decision.
It appears that having reached this point, further discussion is unlikely to
[mailto:] On Behalf Of Anatole Klyosov
Sent: Monday, February 15, 2010 12:16 PM
Cc: Anatole Klyosov
Subject: Re: [DNA] TMRCA assessments
>From: "Alister John Marsh" <>
>Yes, I think we are making progress. My responses to your latest comments
>are as follows...
Unfortunately, we are not making progress.
If after my four or five explanations that back mutations produce negligibly
small contributions to overall mutations in the first 650 years (and
practically do not affect TMRCAs in that time period), and their
contribution up to about 2,000 ybp is also within the margin of error, and
after all those concrete figures which I gave here describing their
contribution, which is indeed close to nothing - if after all of that you
still insist that their contribution is significant (otherwise why talking
about it), I am giving up. There is no point to continue.
I just add a few small things.
>BACK MUTATIONS: (...) I will explain to you what I was meaning when I said
>I had used a "little
bit of basic maths". (...) By my rough calculations, this means there is
about 10% chance that one
person of the 9 will have two mutations on one marker, so about 5% chance
that there will be a back mutation.
You "basic maths" in incorrect, and these calculations are not just "rough",
they are plain wrong. A contribution of back mutations is not linear (such
as 50% in your case compared to "forward" mutations), but exponential. That
is why we do not see them for a loooooong time, and then they start to kick
in exponentially. Not right away and linearly, mind you.
>PROOF OF PARALLEL MUTATIONS/ BACK MUTATIONS: Proof of parallel or back
>mutations depends on context of a cluster of haplotypes. Their existence
>can be proved to credible scientific standards. I won't go into the matter
>in detail now...
You breaking through the open door. Of course back mutations exist. I am
talking NOT on their "existence" but on their contribution to overall number
of mutations in the final dataset which we normally analyze. For your family
history (about 400 years) it is close to nothing. Again, I am not going to
discuss it anymore.
>PICKING ANCESTRAL HAPLOTYPE: Picking an ancestral haplotype to use as the
>basis for mutation counts seems to me rather arbitrary. In the example I
>gave a few days ago, in the case of marker CDYb, it could have had
>ancestral as 37, 38, or 39. I believe you may have assumed it was 39, as
>39 was "modal" for the group, I assumed it was 38, based partly on "R1b
>modal being 38", but it could just as easily have been 37.
The same thing, there is no point to continue. "39" is there 8 times out of
11. 37 - two times, and went to a separate, small branch. 38 happens only
once among 11. I do not want to discuss clearly biased ways of
>LOCATION OF HAPLOTYPE D IN MY EXAMPLE TREE:
Dear Andrew, I just cannot go through all possible detail of your family
tree and detailed family history with lots of names and family events. I
tried to help you out being absolutely neutral and unbiased, and based on
principles of DNA genealogy. You have apparently your own agenda. I just
cannot accept those things.
Best regards, and I wish you good luck with your studies.
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