GENEALOGY-DNA-L Archives

From: David Faux <>
Subject: [DNA] Mutation Rates, MRCA, and the Real World
Date: Sat, 31 Jan 2004 23:03:16 -0800 (PST)

Dear List:

I noted a "real world" example in a recent post that begs for a sensible explanation. One way to approach the 25 / 25 R1a match between two individuals with different surnames (Williamson and Blance), whose ancestors come from Shetland, is to check the predictions via Time to Most Recent Common Ancestor calculations.

A very helpful example is http://nitro.biosci.arizona.edu.ftdna/25-0-0.html by Dr. Bruce Walsh.

Here he uses both "infinite alleles" and "stepwise" models and mutation rates of .002 / marker / transmission as well as a .004 rate. Since the geographic area is small, the haplotype is extremely rare, and Shetland used patronymic naming for Norse families until recent times, the two men probably have an ancestor in common and the question to be answered is when.

Both models offer virtually identical results, it is the proposed mutation rates that offer variability. If one accepts the .002 rate, the MRCA is between 0 and 37 generations at the 95% confidence level; 0 and 19 generations using a .004 mutatiion rate.

Now, 37 generations would bring us to about 1200 years ago - about the time when the first Norse Vikings settled in Shetland. Am I missing something? This means that the two men could be brothers, or descendants of the same Viking.

Can anyone tell me how this is helpful in genealogical research?

David.


Dr. David K. Faux, P.O. Box 192, Seal Beach, CA, 90740, USA



www.davidkfaux.org

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