Ed, the conclusion that the most recent common ancestor of Barton Lineage I was born no later than the 1620s is based purely on paper trails.?
I use the FTDNATiP calculator only as a reference tool to see if there is reason for hope - or doubt.? My experience with the range of statistical probabilities certainly affects my reluctance to put much stock in the statistics - as the ranges in the probabilities are so very wide.? I am also cautious about FTDNA's mutation rate - as it is considerably higher than what we have seen in Barton Lineage I.
Here are our two extremes:
1. My uncle and I are 41/43 - using RG's test.? This is 1.5 generations.? ?(we have learned through extensive testing that my father generated one of the two mutations and I generated the other.)?
From DNA calculations, the probability of my uncle and I being related in 1.5 generations is
- 1.8% at .004 mutation rate
- 0.3% at .002 mutation rate
Looking at it another way: a 50% probability of our relationship, would require
-? ?8.1 generations at .004 mutation rate
- 16.1 generations at .002 mutation rate
2. My uncle and Richard Barton are 43/43.? (they don't share a common ancestor any later than that one born in the 1620s.? My guess is that it was earlier.? The least it could be is 10 generations)
The probability of their relationship in 10 generations is
- 82.1% at .004 mutation rate
- 96.8% at .002 mutation rate
If you used only the above DNA test results, you would assume that my uncle and Richard are much closer related than my uncle and me - and you would be very wrong.? We have to give careful valuation to the paper trails - as clearly, my uncle and I are much more closely related.
Another aspect - WHICH markers you have been tested on also makes a difference.?
Richard and I are 35/37, 40/42. 41/43 and 45/48.? I estimate that my Uncle and Richard are 36/37, 41/42 and? 47/48 and that my uncle and I are 36/37, 41/42 and 46/48.? Only one of the three mutations in this analysis is common to FTDNA and RG - each of the other two show up in only one company's tests.
If you compare at 42 markers (RG26 + FTDNA37) - my uncle and I are 41/42 and my uncle and Richard are (estimated) 41/42 - identical separations.
Only at 48 markers are my uncle and I (46/48 estimated) closer than Richard and me (45/48).? But, my uncle and Richard are still closest (47/48 estimated)
BOTTOM LINE: use mutations and genetic separation as a guide - not a precise calculation.? And, when you cane - compare each man to the ancestral haplotype instead of man to man and identify the mutations as specific information, not simply differences.
ps? I used this calculator:? http://www.moseswalker.com/mrca/calculator.asp?q=2
as I needed one that would deal with many variations