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Archiver > DNA-R1B1C7 > 2009-12 > 1260376681


From: "R. C. Mac Donald" <>
Subject: [R-M222] modal=ancestral?
Date: Wed, 9 Dec 2009 11:38:01 -0500


Sandy,

I don't mean to derail the discussion with tangential questions, but you said something that I believe needs clarification. You proposed for the sake of argument:
"Let us pretend that we know beyond doubt that the M222+modal is exactly as estimated, ie that the entire population of M222+ is descended from one man with the haplotype 13,25,14,11,11...."

I don't know if anyone is arguing for this position, but it appears to me to involve a mistake about the significance of modal haplotypes.

Knowing what the M222+ modal is only tells us what are the most common STR values for each marker among those of us with a specific SNP mutation, not what those values were for the first man who had the mutation. The modal will slowly but steadily change over generations but the values for the first M222+ man can't.

Now, should we assume that his haplotype was 13,25,14,11,11... because those are the prevalent values now, or even because (if we could know this) they have been and will the prevalent values among all M222+ men from the first to the end of time? Then what about those of us (about 7% of M222+ the last time I checked) who have 13,24,14,11,11...? It could be we descended from someone who had a reverse mutation, but it's also possible and, I think, more likely that the first M222+ man had the R1b1 modal value of 24 and one of his descendants, who somehow out-propagated his brothers and/or cousins, was the first with a value of 25.

Or is there something I'm overlooking? I can't claim expertise in any field relevant to this question; I hope, by the way, that this doesn't devalue my saying that I agree with your point about the greater significance of off-modal matches.

R.C.


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