Archiver > GENEALOGY-DNA > 2004-12 > 1104270589

Subject: Re: [DNA] MRCA = 800 AD
Date: Tue, 28 Dec 2004 21:49:49 +0000


Does that mean you could or could not write a formula, taking into account all the factors you have noted? Dennis Garvey's charts would be a starting point for harvesting data.

David F.

-------------- Original message --------------

> The rarity of a marker value is just a signal that something useful
> is sitting there. The interpretation must depend more on the age of
> that marker value and less on the degree of rarity itself. In other
> words, if an allele is rare because it never existed at all until
> 500 years ago, then sharing that allele means a relatively high
> probability of MRCA within the past 500 years. (Of course, it's
> more complicated than that, but you get the picture.) On the other
> hand, an allele that is rare but has been floating around for
> 10,000 years doesn't do much to tilt the odds of a recent MRCA.
> John Chandler
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