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ironroad41
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« on: June 21, 2012, 04:23:19 PM »

I have made a few TMRCA estimates from the FtDNA Z253 data set.  I used 25 dys loci (of the first 37) and two data sets.  1. 3 entries with similar allele values and all having a 13 at 388.   I estimate a common ancestor c. 780AD.  This set of 3 has a 12 at 393, a 23 at 390, a 13 at 388 and several other rarer values at other dys loci.  2.  The set of 22 entries, all Z 2553+,L226-.  Using the same dys loci I got a TMRCA of 1200 BC.  Note this set had two entries with 426 = 13.  They are probably related, if so that would reduce the TMRCA to about 700 BC.

Finally, one last calculation resulted in comparing the two modals.  I found a 3060 (2560) years difference.  I would estimate a common ancestor about 1800 to 2300 BC for these two modals.  I believe this is 2 to 3K years older than current/previous estimates of when the Z253 founder was born.  Note: I used M. Heinilas mutation rates.
« Last Edit: June 22, 2012, 06:54:47 AM by ironroad41 » Logged
ironroad41
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« Reply #1 on: June 22, 2012, 06:51:44 AM »

The equation I use for this calculation is at its simplest:  TMRCA = (#of mutations)/mutation rate for each dys loci.  In practice the equation is written as: TMRCA = (1/# of entries) X 1/(# of dys loci) X 31,000 X ((#of mutations)/mutation rate)).  This equation is computed for each dys loci and the results for all dys loci are summed.  Note this permits an estimate of the SD of the computation by taking, individually, the square root of the squared difference between the TMRCA and the estimate for each dys loci and summing those differences.  Slow mutators usually introduce larger deviations.  Note that I use 31 years/generation and multiply by 1000 such that the denominators are usually a whole number or a fraction thereof.
« Last Edit: June 22, 2012, 06:53:10 AM by ironroad41 » Logged
ironroad41
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« Reply #2 on: June 25, 2012, 02:32:03 PM »

I have identified another subset within R Z253+ entries.  There are seven entries with a 13 at 426.   In both cases one of the 388 and 426 entries has been tested Z253+ and all other known SNP's negative. This creates therefore 3 subsets with this SNP pattern.  The respective TMRCA's of the three subsets are: 388 = 13; 780 AD; 425 = 13, 1280 AD and the eleven rest are 730 BC.

It is not at all clear to me how to combine these three TMRCA's?  Further, based on what I observed in the Ian Cam, at the founders birth a mutation occurred.  In this case I don't know which mutation occurred either.

Further confounding all this analysis is that I have a 10 at 632.  No other R-L21 has that value to my knowledge.  It is the second slowest mutator of the 111 and is truly a "black swan".
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ironroad41
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« Reply #3 on: June 27, 2012, 10:09:39 AM »

I could not come up with a rational way to add the modals of the three sets of data.  Therefore I used all 21 R Z253+, all else negative.  I used the first 37 dys loci and omitted all the palindromic dys loci, leaving 25 dys loci.

Approach:  I used only one 426 mutation and one 388 mutation because I believe the others are not unique mutational events.  I now estimate that the TMRCA is about 1200 BC with a fairly wide SD due to the slower mutations. (426, 388 and 392, 455 and 437).  I would guess that this is a fairly conservative estimate since most of the palindromic dys loci are different and this would add to the estimate in some amount if included. This estimate could be improved if I had data for all 111 dys loci for all entries.  One observation is that there seem to be more mutations in the first 37 and last 44 than the middle 30 dys loci.  Why this is so is a TBD, although there are many slow mutators in Dys loci 38 to 67.  Note:  the 5 slower mutators account for 60% or so of the total TMRCA.

This result suggests that the R - L21 set of TMRCA estimates may be somewhat longer than current results suggest.

edit:  I know there are concerns about hidden mutations at the faster mutators.  If I just used the 5 slowest mutators rather than 25, then the result becomes 7000 BC, which is a whole new ball game if it is anywhere near correct.  note that this approach is somewhat similar to Klyosovs use of slow mutators except in this case I am using the estimated mutation rate of each dys loci.  Also note that these all appear to be independent mutations, 1 each at the slowest is simple, in the case of 392, there are two different values.  455 and 437 could be non unique, but it doesnt' appear to supported by the supplied family information?  This data suggests that hidden/back mutations are more of a problem than currently understood.
« Last Edit: June 27, 2012, 01:29:14 PM by ironroad41 » Logged
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