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Project Results

Initial test results for the current sample of 186 participants indicate that all O MAHONY of the name do not share a common ancestor.  There are many possible reasons for the variety of haplogroups found within the project.  Read on!


O’Mahony Surname Project Participants’ Results Report


Go to “How to interpret test results” for help understanding the technical details of how to derive meaning from differences in the numbers found in the tables:


R-1b – CTS4466 : The Main Haplogroup of the Eoghanacht Rathlind





CTS4466 is the SNP that defines the Irish Type II subclade. In 2011, the Walk Through The Y test offered by Family Tree did not produce the expected breakthrough, but by late 2012, the National Geographic offered a  more comprehensive Geno 2.0 test as part of a worldwide study. That finally gave us success with two SNPs – CTS4466 and CTS5714.  Later the 1000 Genome project added two further SNPs – CTS3974 and CTS8358. Since then, more advances (results of the efforts of the Full Genome Corp and the increased sophistication of the Big Y test) have been recorded as participants upgrade from the  BIG Y 500 to the Big Y 700 test.


Of those who have tested at the higher level (Big Y 700 and those who test at 67 or 111 markers and who match the CTS4466 results), we can see that these comprise the major grouping within the project who are of Eoghanacht origin.  This group will find that O Donoghue and O Sullivans will be found among their matches.


“The principal Eóghanacht names of O’Sullivan, O’Donoghue, O’Mahony, and O’Keeffe, along with O’Moriarty and O’Dennehy (or present day variants thereof), are all found in significant clusters under SNP S1121”. ……… (although the positions of the O’Sullivan and O’Moriarty clusters there under are not consistent with the ancient genealogies) but are almost entirely absent under the parallel lineage headed by SNP Z21065; the Z21065 (and Z16259) O’Donovans and O’Regans, on the other hand, are entirely absent from the haplogroup of S1121.

All those DNA-testing participants who find themselves in these clusters can therefore consider themselves as sharing Oilioll Olum as a common ancestor, or if Oilioll Olum is to be regarded as a semi-mythical or fictitious character, someone of his ilk and era.” (McCarthy, N.)


Many participants have a result R-M269 which they share with approximately one million men of European heritage. Further testing would be necessary to confirm their precise terminal SNP.


Some additional results for other participants:


Haplogroup R-L226


“Using geneticist Anatole Klyosov's methods, a calculation using 336 haplotypes of 67 markers conducted in September 2014 gives a figure of 1450 ± 150 years to the most recent common ancestor (MRCA). The MRCA for this cluster lived between 350 AD and 650 AD.”


“The Irish Type III website, the Dalcassian R-L226 from Clare, Limerick and Tipperary, looks at the origins and age of the R1b cluster called “Irish Type III,” believed to be that of the Dal Cais sept that lived in the area of Ireland called Thomond.”


Names associated with this haplogroup are O’Brien, Casey, Kennedy and Hogan.


Many men with the L226 DNA of Brian Boru do not have historical Dalcassian surnames. The major names are: O Mahony, Crow, McCraw, McGraw, Hart, Butler, Callahan.  The presence of R-L226 in the O Mahonys could be explained by a number of Sadhbh being accompanied by a number of her male relatives as retainers on her marriage to Cian and their subsequent absorption into the O Mahonys. A simpler explanation could be a name change by choice to avail of a land inheritance, or an adoption.


Haplogroup R-FGC5494 (22 participants)


There are currently O Mahonys who fall into this haplogroup and they are encouraged to join the specific project  dedicated to their haplogroup at : ...


… where they say FGC5494 is not part of that set of old Gaelic haplogroups identified early on. But it is nonetheless well dispersed in England, Scotland, Wales, Isle of Man, and Ireland, with (so far) a smattering on the European continent. FGC5494 entered the British Isles from the continent.


To quote the Collins project : “ R1b subclade DF13 is the parent of several major haplogroups with significant representation in the British Isles. Among those major haplogroups under DF13 are some of what were called the "Gaelic" ones - Dal Cais, North Irish, South Irish, etc. Those groups, which turned up in early yDNA research, are now better known by their SNPs: R-L226, R-M222, R-CTS4466, etc. At one time it was thought those groups in particular originated within Ireland. That view has shifted somewhat.”

 ( )

Haplogroup R-U106 and subclades (3 particpants)

“R1b-U106 is a patrilineal descended family that appears to descend from an ancestral R1b group located among or near the Yamnaya culture, north of the Black Sea area. The group rose to significance in the area of present Germany and the surrounding areas probably a bit before 3000 BC.  Although U106 is found all over Europe, and in countries that Europeans have migrated to, it is most significant in Germany and surrounding countries, Scandinavia, and Britain. In its time-frame of 3000 BC, U106 likely arose in the Corded Ware culture. Depending on which branch of U106 a member descends from, the people on that branch adapted to a variety of different cultures along the way, including various derivatives of Slavic, Latin, Celtic, Belgae, Saxon, Viking, and other cultural groups. U106 is a family, not a culture. “

Halpogroup E (3 participants)


The E-M215 haplogroup has two ancient branches that contain all the known modern E-M215, E-M35 and E-M281 subclades. Of the latter two E-M215 subhaplogroups, the only branch that has been confirmed in a native population outside of Ethiopia is E-M35. E-M35 in turn has two known branches, E-V68 and E-Z827, which contain by far the majority of all modern E-M215 subclade bearers. The E-V68 and E-V257 subclades have been found at highest frequencies in North Africa and the Horn of Africa, and also at lower percentages in parts of the Middle East and Europe, and in isolated populations of Southern Africa. (Wikipedia)


Haplogroup I2

Haplogroup I2 might have originated in southeastern Europe some 15,000 to 17,000 years ago. The P37.2 subgroup seems to have originated about 10,700 years ago (plus or minus 4,800 years). However, the known members of this group seem to share an ancestor who lived more recently, approximately 8,000 years ago (plus or minus 4,000 years).   Source: Wikipedia, Haplogroup I2

Haplogroup I2a1-P37.2  


Two examples of I2a1 have been found in the DNA of Neolithic farmers. They were among the burials in the Cave of Treilles in Aveyron, in the South of France. The Treilles culture of c. 3000 BC is the very last phase of the Neolithic in the region before the arrival of copper-workers and the Bell Beaker culture. 4 Ken Nordtvedt considers their haplotypes consistent with I2a1a -M26.

Source:, Haplogroup I


Haplogroup I- M253


Haplogroup I-M253, also known as I1, is a Y chromosome haplogroup. The genetic markers confirmed as identifying I-M253 are the SNPs M253,M307.2/P203.2, M450/S109, P30, P40, L64, L75, L80, L81, L118, L121/S62, L123, L124/S64, L125/S65, L157.1, L186, and L187.[6] It is a primary branch of Haplogroup I-M170 (I*).

The haplogroup reaches its peak frequencies in Sweden (52 percent of males in Västra Götaland County) and western Finland (more than 50 percent in Satakunta province).[7] In terms of national averages, I-M253 is found in 35–38 per cent of Swedish males,[8] 32.8% of Danish males,[9] about 31.5% of Norwegian males,[10] and about 28% of Finnish males.[11]

Haplogroup I-M253 is a primary branch of haplogroup I* (I-M170), which has been present in Europe since ancient times. The other primary branch of I* is I-M438, also known as I2.

3 Haplogroup Cousins.png

2019: (L-R) Former Taoiseachs Greg Mahony (Aus),  Dr. Finbar O Mahony,  Colman O Mahony:  CTS4466 one and all.

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