Archiver > GENEALOGY-DNA > 2010-02 > 1266253055

From: "Lancaster-Boon" <>
Subject: [DNA] Parallel and Back Mutations
Date: Mon, 15 Feb 2010 17:57:35 +0100

Dear Anatole

You wrote to John Marsh doubting the existence of obvious BACK mutations
within a genealogical timeframe in real family trees:-

>Prove, please. I would love to learn something VERY unusual (whispering
to a side: no chance with those "back mutations"...)

He then started discussing an example and you wrote a response which once
again managed to combine admission that you had not examined the data, along
with yet another unnecessary implied accusation of dishonesty (having an
"agenda") on this list:-

>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.

This is a little similar to what happened with previous attempts to
communicate concerning real examples about this subject. But no problem.
Let's keep trying. But I guess there is no point trying to talk about real
data until we get further understanding of each other on the basics of your
theoretical approach. This takes time given the differing word usages and so

Concerning the term "PARALLEL mutation", which you said you had no clear
definition for, after receiving a description you wrote to David Ewing:-

> Why wouldn't you call them "perpendicular" mutations?

This and other remarks raise doubts about whether you understand how the
term "parallel mutation" is being used and just like you mention to others,
it will be important that you keep people's terminology in mind and try to

A parallel mutation is the exact same mutation (example DYS393 from
ancestral 13 to derived 12) happening twice, in parallel, in two different
branches of one family tree. I guess the rest of us think the metaphor works
very well in this case: identical events happening in the same timeframe but
in two different places are normally called parallel events in English.

Here is an example of a parallel mutation:
1. Ancestral DYS393=13.
2. Using 67 markers, two very clear clades can be distinguished, consistent
on nearly all markers.
3. However, DYS393=12 appears in part of both clades.

I am hoping you will not non-answer this by saying it is fuzzy or not a real
example. It is easy to find real examples where it can be stated with a high
degree of certainty that such a thing has happened. We can give examples,
but this always leads to the discussion breaking down from your side.
Anyway, for the sake of allowing conversation to continue I think it is
reasonable to accept that people are telling the truth that such examples
exist, or answer as if they are.

You corrected David:-

> I said that back mutations do not contribute into a TMRCA calculations
during the first 26 generations, and contribute very little, within the
margin of error up to 2,000 ybp. Regarding "parallel" mutations I only said
(or implied) that I do not want to pay attention at them because they are
non-issue. If they cause separate branch formation, fine, I just analyze
that branch. I do not call them "parallel" since they are just mutations, as
anything else.

Maybe this remark is a good lead. I see that in his response, David, like I
think most people, thinks that when you wrote about back mutations, you must
also be writing about parallel mutations. There is a good practical reason
for this. It is often possible to see that back mutations and/or parallel
mutations have happened, but hard to tell which has happened where, and that
is indeed the whole point of raising this issue. They are basically
equivalent problems. They have the same affect upon attempting to build a
"haplotype tree".

You are of course right that in SOME cases you can see pretty clear apparent
branching without being the obvious parallel and back mutations ruining the
clarity of the picture. No problem. But then there are many more other cases
where they do mess things up (again, yes I can give real examples and I hope
you will just believe me at least for the sake of this discussion) and then
what you see are datasets which show that one or both have happened.

But, why do you make a distinction between parallel mutations and back
mutations? Or is this a misunderstanding? Aren't you just saying that you
ignore both?

Best Regards

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