Andrew Griffiths: I began my own genetic journey 2015 with an STR (short tandem repeat) Y DNA test of the kind called Y-67 and later the Y chromosome test call Big Y-500, which was offered by Family Tree DNA, confidently anticipating that I would belong to one of the typical Irish haplogroups (Irish Type I, II or III).
To my surprise, my haplogroup turned out to be R-L1065, which is associated with the Dál Riata Kingdom, which flourished in southwestern Scotland in the 6th Century AD, and most of my closest "matches" (i.e., cousins based solely on the Y-chromosome) bore the names of Scottish clans, whose ancestral lands clustered around Loch Lomond and Perthshire.
As far as I knew, my own patrilineal ancestors had lived in County Tipperary since the late 1700’s, so the second surprise was that several Griffins shared my Y-chromosomal signature, whose ancestors hailed from County Kerry. There were no matches with Griffins or Griffiths from anywhere else. Further Y-DNA analysis revealed more specific haplogroups of R-S764 and R-A13315.
This mutation occurred about 1,300 years ago in Scotland and is common to several different clans originating from the southwestern Scottish Highlands, including the MacDonalds, the MacRaes, and the McCoys.
All of these clans have characteristic SNP’s of their own, but none of these are present in my own genes, suggesting that the branch with my "MacGriffin" ancestor separated from the other clans at an early date, probably over 1,000 years ago, which was well before surnames became customary in Scotland in the 13th Century.
Having exhausted the catalogue of "known" SNPs, the next step on my journey into the past was to take another test of the kind called "Next Generation Sequencing" (NGS), which is a detailed examination of the Y-chromosome to discover "novel" SNPs, which have not yet found their way into the literature. The test was called the "Big Y" and eleven new SNPs were found in my genome and given names of the type "A133nn."
This chart (below) shows the relationship between nineteen "Griffin" cousins, who have all taken the "Big Y" test (or equivalent), and how they diverged from some Scottish clans over 1,000 years ago. The dates allocated to some of the branching points are speculative.
R. F. McKinley (far left on the chart under the A13318 branch) is a key person in this discussion, because he is the closest relative of the Kerry Griffins (found so far), that can trace an unbroken male line back to the time before the Griffins arrived in Munster. In other words, according to our present state of knowledge, the Griffins are more closely related to the McKinlays of Callander in Perthshire than to any other Scottish clan.
The dates are very approximate and we are only dealing with probabilities, but another conclusion to be drawn from this chart is the ancestor to the Griffin paternal line, unique to County Kerry, left Scotland sometime during the Middle Ages before the 17th century.
There is another important fact to be gleaned from Y STR DNA analysis: the Y-chromosomes of the Kerry Griffins have a characteristic value at one particular STR marker, called DYS590. Instead of 8 tandem repeats, which is usual for the R1b haplogroup, this marker has only 7 repeats in members of the R-A13315 haplogroup. Since this is a very rare mutation, it can be used as near confirmation for someone testing at the FTDNA Y-111 level that they are, or are not, descended from the paternal Griffin line unique to County Kerry. The DYS590 deletion must have occurred at about the same time as the exodus from Scotland, because it is present in the DNA of all the Kerry Griffins but has not been found in any of our relatives with whom we have a common ancestor that predates the emergence of the "Griffin of County Kerry" SNP R-A13315.