Wednesday, May 4, 2011

Comparing 111 Markers in Y-chromosome DNA Research

I have had my 111 marker Y-chromosome DNA results back from the lab for a couple of weeks. That was exciting but it was essentially meaningless. DNA test results for genealogical purposes only take on significance when there are others in the database with whom meaningful comparisons can be made. Last night I noticed that my first match was with Herb McDaniel. Herb and I have previously had matches at lower resolutions. We matched on 35 of 37 markers and 64 of 67 markers. Our new results show that we match on 102 of 111 markers.
What does this mean? Are we now shown to be more or less likely to have a common male ancestor within genealogical time? Genealogical time is defined as the era in which most individuals have had surnames.
Both Herb and I have solid paper trails of our respective paternal lines that go back 8 generations. Also both of us have been able to triangulate our first 67 markers of our Y-chromosome DNA enough to be reasonably confident that each of us exactly matches those markers of our 5th or 6th great-grandfathers. This knowledge allows us to make a slight adjustment in the information provided by FTDNATiP™ which is employed by Family Tree DNA to create probabilities of a shared common ancestor within the last so many generations. In our case we believe that Herb's paternal McDaniel ancestor and my paternal Dowell ancestor were exactly as many markers apart eight generations ago as Herb and I are today. Well we believed this prior to getting the results back on markers 68 to 111. Only time will tell if we can further refine our thinking based on these latest results.
Below are four different columns probabilities that Herb and I share a common male ancestor. Each of them are listed in this table at 4 generation intervals. However, they could easily be displayed for every generation. Again, based on a combination of paper and DNA research, we do not believe we are related within the last 8 generations. In general the addition of markers 68 to 111 appear to strengthen the probabilities that we share a common male ancestor over all the intervals but particularly after 10 to 12 generations.
Generations To Common Ancestor
67 Markers
(64/67 match)
67 Markers
111 Markers
(102/111 match)
111 Markers

* "The FTDNATiP™ results are based on the mutation rate study presented during the 1st International Conference on Genetic Genealogy, on Oct. 30, 2004. The above probabilities take into consideration the mutation rates for each individual marker being compared."


  1. I have a similar dilemna, which proves that not even convergence can explain this..I have matched a "Kelly" surname from 12-111 markers Y-DNA, with genetic distance never above 3 until Y-111 (102/111 match)..My other only advanced match was a 61/67 match for Y-67 to a "Fenoughty" surname (a variation of my ancestors "Finnerty/Feinaughty" surname from Ventry records)..He did not test to 111 markers, and is not responding to any e-mails..There were 11 other "Kelly" males I matched at 12 markers, so this "Kelly" connection appears to be neither due to coincidence nor convergence..I was asked to join the "Kelly DNA Project" and to test the SNP "DF27".. Results in a week or so..B

  2. Brian, thank you for sharing.
    It looks like short tandem repeats (STRs) alone may not resolve your relationship with the Kellys.
    Herb McDaniel and I have recently turned to single nucleotide polymorphisms (SNPs) for more information. Until the last year SNPs could not be tested in enough detail to have any promise of helping us solve relationship questions within the last several hundred years. Herb and I were among the first to take the BIG Y test. It confirms that our ancestors were part of the same subclan. However, preliminary results seem to show that our common male ancestor could be as far back as 700 to 1,000 years ago. We will only be able to refine this estimate as more members of our subclan are SNP tested.

    1. Thank you, Dr. D....I have been told that haplotype convergence can not explain my 11/12, 24/25, 34/37, 64/67, 102/111 match with the same male with a different surname..He is deceased, and I may have to find an "in-betweener" male from that Kelly line. I have SNP results pending for "P312", " L21", "DF13", " DF63", "DF19", and " CTS4466"... I seem to fit the modal for "South Irish/L21"... I am confirmed " DF27-" by FTDNA...Lab results for the others should be back in 6 weeks or so...My connection to this "Kelly" is strange, indeed...I definitely meet the criteria for "DYS19 15, Haplotype #16"... I have seen other " L21" males with DYS19 15, DYS393 13, and DYS390 24..Not a lot, seeing that DYS19 15 is not common...I will be taking the "Big Y" for research sake...I will never find out my "Kelly" connection, seeing that our common male ancestor was from 20-24 generations ago...B

  3. Hey, Dr. D!! The "Big Y" test indeed showed that my Kelly Y-match (11/12, 24/25, 34/37, 64/67, 102/111) is also R1b•DF21>S5488>S20620...We are the only 2 men who have that terminal SNP...This is great news, as it proves that our families share a common paternal ancestor...B

  4. Good morning Brian,
    Congratulations on your results. With great haste we make slow progress! At least we are getting there.

    Have you explored your "Shared Novel Variants" on your results page at FTDNA? I described this process a few months ago: I you scroll to the bottom of this drop down menu, this will allow you to start with your closest matches and work your way back in time.

    Your results may be under reported in that column. My R1b-S1026 subclade project, has that issue which we are working with FTDNA tech support to resolve. Most of our matches do show up there but apparently results for a few members do not appear to have indexed properly.