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Archiver > DNA-R1B1C7 > 2007-08 > 1186857361


From: "David Ewing" <>
Subject: Re: [DNA-R1B1C7] Network.exe
Date: Sat, 11 Aug 2007 12:36:01 -0600


Well, I've done some TMRCA calculations quick and dirty, just using the
R1b1c7 McLaughlin, Dougherty and Ewing modals on various subsets of the
markers, using mutation rates as estimated by Chandler. If you weren't
confused before, this should do it.

Using the slowest 15 markers in the 37-marker FtDNA panel with mutation
rates averaging 0.00088, there are very few differences between these
modals. The McLaughlin and Dougherty modals are identical to one another and
differ from the R1b1c7 modal only at YCA-IIb = 22. The Ewing modal differs
from the R1b1c7 modal only at DYS19 = 15. This puts Ewing at genetic
distance 2/15 from McLaughlin/Dougherty. If we use the MRCA calculator I
sent the link for, a 13/15 match and an average mutation rate of 0.00088, we
find that the most likely TMRCA is about 85 generations back and the chance
of that is about 25%. There is a 45% chance that the MRCA is within the last
100 generations; I'd tell you what the 50% level was, but it's off the
chart.

Using the slowest 23 markers in the 37-marker FtDNA panel with mutation
rates averaging 0.00148, Ewing differs from the R1b1c7 modal at DYS 19 and
DYS 442; McLaughlin/Dougherty are still identical to one another and still
differ from the R1b1c7 modal at only YCA-IIb; so, the genetic distance
between Ewing and McLaughlin/Dougherty is 3/23. Using the same calculator,
we find the most likely TMRCA is about 48 generations, the chance of that is
about 21%, and there is a 50% likelihood that the MRCA was 58 generations
ago or fewer.

Using the slowest 32 markers in the 37-marker FtDNA panel with mutation
rates averaging 0.00265, Ewing differs from the R1b1c7 modal also at two
more markers: DYS439 = 13 and DYS 456 = 18. McLaughlin and Dougherty are
still identical to one another and both differ from the R1b1c7 modal at the
additional marker DYS460 = 12. On this panel, the genetic distance between
Ewing and McLaughlin/Dougherty is 6/32. The calculator we have been using
only gives graphs up to genetic distance 5/32, but eyeball extrapolation
suggests that the most likely TMRCA is about 40 generations but that the
chance of that is less than 15%.

Using the entire 37-marker FtDNA panel with mutation rates averaging 0.00492,
Ewing differs from the R1b1c7 modal at 3 more markers: DYS 449, CDYa and
CDYb. McLaughlin/Dougherty are still identical, and differ from the R1b1c7
modal at one more marker, DYS 460. On the full panel, the genetic distance
between Ewing and McLaughlin/Dougherty is 10/37. The calculators I sent the
links for don't work with genetic distances this large, but using the
variable per locus rates that FtDNA supplies, Doug McDonald's utility
calculates Ewing and the other two have a MRCA 31 generations ago. If
instead we use the 0.00492 average calculated by John Chandler as a constant
average, the MRCA between these two groups goes to 34 generations. And if we
use the much bandied about rate of 0.002, the distance goes to 84
generations. You can see how important the mutation rate assumption is.

David Ewing

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