We have a Match – Mcneill and Beyond

Updated 28-Jun-2024

This is part of Mcneill and Beyond - a Memoir

This is a longish response/open letter to the few folks who contact me regarding genetic genealogical research, usually about some kind of match we have discovered in our Y-DNA.

A Match at 12 Markers

Any matches on markers (using FTDNA) indicates some amount of probability of a common ancestor within a certain number of generations, based on mutation rates.

If we have a match at 12 markers (12 out of 12) but not higher than that -- that is, there are more than 2 mutations at the 25 marker panel, 4 at 37 and 7 at 67. The probability of our Most Recent Common Ancestor (MCRA) within a certain number of generations, is as follows:

  • 4 generations 33%
  • 8 generations 55%
  • 24 generations 91%

I've got a fairly good 12 generations of genealogy (of course one can always be wrong, but I've got cousins and uncles back five generations with genetic material matching). I've got much better matching with some other/previously unknown folks who are not in our personal stories.

I've recently updated my profile to 111 STR markers. Only two matches in the database (as of 30 Oct 2016) are within a reasonable deviation of markers (one at 7 and one at 9). Interestingly, at 104/111 is probably related and 103/111 is only possibly related, which indicates a dividing line. For a 104/111 STR marker match, the probabilities of relatedness within a number of generations are:

  • 11 generations 50% ~ 440 years
    • 1660 CE (Contemporaneous with oldest known relative in Northern Ireland)
  • 17 generations 90% ~ 680 years
  • 19 generations 95% ~ 760 years
  • 22 generations 99% ~ 880 years

Note that for haplotypes, there is a more accurate mutation rate that is now used.

Update, now with three relations with 4, 7, and 9 mismatches at 111 markers, it seems that 0.5% per generation is the right order of magnitude. This means around 8 mismatches would indicate a probable match at 16 generations.

The Possibilities of Probable Relatedness

  • We could be related through some common ancestor/branch from the family in the US, but I do not have comprehensive genealogies for everyone descending in the US from the 1725 immigrant ancestor.

  • There could be a "Non-paternity event" for somebody along the line, which means we would not be able to uncover that from a known genealogy. Note that this could have occurred in either my line or yours, or both. See for probabilities.

  • Note that the length of a generation impacts both mutation rates and NPE probabilities. For my patrilineal line I've got an average 39.5 years per generation. This is very different from the 25 years and 30 years/generation that most models have. My guess is around 30% on average back to 1600 (10 generations). Every 10 generations/400 years = another 30% probability of NPE.

  • We could be related previous to my Immigrant ancestor leaving Northern Ireland (~30-50% chance -- because our markers have less matching at the higher numbers, e.g., 25, 37, 67, and 111). The genealogical story ends back in Northern Ireland, though we can likely trace back to Argyll before that. I've got some potential places to look at (graveyards in Northern Ireland) but I haven't tried to extend that part of the story yet.

  • Note that physical description is not all through the Y chromosome, as much of that can come from mothers, esp. balding patterns, which are generally shared between male offspring and their maternal grandfather.

There is a lot more info I've compiled as this area of research is interesting to me and I've been doing these genetic tests on and off for over a decade. My own story and the most credible tale that comes out of the genetic genealogy is the (incomplete) memoir Mcneill and Beyond of which this open letter is a part.

You may want to skip to the second part, where I discuss the haplotype groups and most-recent-common-ancestor relations. Long story short, my genes are most likely Anglii, as in the Angles (as in the Angles and the Saxons). Certainly my "Mcneill" which is Gaelic Scots is not a match for my genetic genealogy, and so I definitely have an NPE for any of the following reasons as given at: . Note that NPE simply means a paternal name (and the genealogy around that) is not literal.

Non-Paternity Event Causes

  • Illegitimacy outside marriage: boy taking maiden name of mother
  • Infidelity within marriage: boy taking surname of mother’s husband
  • Re-marriage: boy taking surname of step-father
  • Rape: boy taking surname of mother or partner
  • Changeling, surrogacy, sperm donation, unintentional embryo/baby swap: boy taking surname of mother or partner
  • Adoption, incl. ‘hidden’, orphan & foster: boy taking surname of guardian
  • Apprentice or slave: youth taking surname of master
  • Tenant or vassal: man taking surname of landlord or chief
  • Anglicisation of gaelic or foreign name: man taking translated/phonetically similar name
  • Formal name-change, e.g. to inherit land: man taking maiden name of wife or mother
  • Name-change to hide criminal past, embarrassing surname, or a stage name: man taking unrelated surname
  • Informal name-change, alias, by-name: man taking name of farm, trade or origin
  • Mistake in genealogy, or in DNA analysis

Next Steps in Genetic Genealogical Research

My suggestion for next steps with testing is to get into specific Terminal SNP testing. You've been put in a general haplogroup but that is not useful enough to locate MRCAs that might make a meaningful connection (in the last 2,000 years or so). There are two main types of testing at FTDNA, one is the marker sets, and the other are SNPs (which identify smaller group mutations). Terminal SNP is a much more precise set than # of marker matches.

In FTDNA, go to Y-DNA > Haplogroup and SNP

The point is that in this highly branched and very wide tree there is a spot at which you do not test positive any further to the right. That is the terminal SNP. Now, they are discovering new stuff all the time, so you can be given a terminal SNP and then a few months or years later another part of the tree will be expanded and you may have a new test to try out. FTDNA is fairly slow at this, and a custom lab called YSEQ that does cutting edge panels (and better prices) but you really have to know what you want there. https://www.yseq.net/

I suggest spending time on FTDNA and in the groups and read up on the science until it makes sense (it took me a while). Ultimately some kind of story can emerge that fits the known genetic and genealogical facts that you have.

You can find a group to join and ask for advice on which test to take next. If you are related to me, they should let you into the Anglo-Saxon Y-DNA group, and you can ask for advice.

Once you are there they will sort you into the chart and you can gain more guidance on the SNP tests to take next. Unless you have money to burn, you don't have to do the Big Y which is a huge set of tests, that try to sort into nearest terminal, though there is usually a test or two to take after that. This test is nearly $ 600 USD as of June 2016.

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