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Archiver > DNA-R1B1C7 > 2009-12 > 1260381702


From: "R. C. Mac Donald" <>
Subject: Re: [R-M222] modal=ancestral?
Date: Wed, 9 Dec 2009 13:01:42 -0500
References: <66669.32915.qm@web50807.mail.re2.yahoo.com>
In-Reply-To: <66669.32915.qm@web50807.mail.re2.yahoo.com>


Yes, reverse mutations do occur, and in the case you describe this is the best explanation for the results you have. But let's look at what this means.

Either your 1682 ancestor had a value of 26 and one of the three lines back-mutated to 25, or your ancestor's value was 25 and two lines mutated to 26 completely independently of each other. The first possibility is the preferred explanation because it assumes only one mutation instead of two.

What I suggesting is the same applies to the question of whether the first M222+ had a 24 or a 25 at that marker. Either he had the usual R1b1 value of 24 and the more successful line of his descendants changed to 25, or he changed to 25 and one of his descendants went back to 24. Again, why assume two mutations to explain what can be expalined by one?
----- Original Message -----
From: Moore<mailto:>
To: <mailto:>
Sent: Wednesday, December 09, 2009 12:25 PM
Subject: Re: [R-M222] modal=ancestral?


The numbers indeed can go up and down.
I have two distant cousins, with a solid paper trail.
The first is =seventh once removed from me, the second= sixth twice removed, but the two are more closely related to each other, sharing a common ancestor several generations closer to each other than me.
Our first 12 markers are as follows:
Me 13-26-14-11-11-13-12-12-12-13-14-29Ed 13-26-14-12-11-13-12-12-12-13-14-29Mil 13-25-14-12-11-13-12-12-12-13-14-29
As you can see, 2 have a 26, the other 25. As the two with the 26 are more distantly related, I believe the 26 to be original of our ancestor in 1682. It is more reasonable that the third one "down-mutated" to 25 since their branch with the second person. So even though 25 is more common, I think the 26 is our ancestral. Perhaps it down-mutated because of some physical properties in the DNA chain that restricts infinitive upward movement (only a guess, as I don't see any 27's anywhere in the community at large.
It is problematic at the fourth marker, where the second and third have a 12, definitely off-modal. It's anyones guess whether my line down mutated from 12 or theirs, more recently related, up-mutated.
Both these positions are slower mutators, it just depends on what generation you test and catch the marker "rolling over" (as on a car odometer) At any rate the markers can mutate up or down.
J Moore

--- On Wed, 12/9/09, R. C. Mac Donald <<mailto:>> wrote:

From: R. C. Mac Donald <<mailto:>>
Subject: [R-M222] modal=ancestral?
To: "dna-r1b1c7" <<mailto:>>
Date: Wednesday, December 9, 2009, 11:38 AM

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.
R1b1c7 Research and Links:

http://clanmaclochlainn.com/R1b1c7/<http://clanmaclochlainn.com/R1b1c7/>;
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