Re: New 59 Marker Test Familytreedna
-
In reply to:
New 59 Marker Test Familytreedna
Nancy Hernandez 3/28/06
The additional markers only decrease decrease TMRCA slightly. 37 markers has reached a point of diminishing returns. Compare the decreases in going from 12 to 25 to 37. The generations in the FTDNA table have to be doubled, since they use a mutation rate twice the actual one:
http://www.ftdna.com/faq2.htmlhttp://www.ftdna.com/faq2.html
If you upgrade and there are no more mutations, it would decrease the number of generations for a 95% chance of finding the common ancestor from 20 to 16 (after doubling the values in the table). Of course, there could be one or two more mutations and the TMRCA would be a little worse.
Given the murkiness of the numbers, something other than a (very unlikely) total failure of the match probably wouldn't make much difference in your strategy. Of course, 5% of the time the TMRCA could be in the very long tail going back many generations.
A big problem with TMRCA calcualtions is that we are applying statistics, which are valuable in assessing groups, to individual cases. They simply don't help in pinning down exact relationships. We have second cousins who are 41/43 matches and 8th cousins who are 43/43 matches.
More Replies:
-
Re: New 59 Marker Test Familytreedna
Nancy Hernandez 3/28/06