DNA Analysis of the Creegan Y-chromosome


DNA comparisons can be used to help determine family ancestry. Y-chromosome analysis is widely used to determine paternal ancestry and mitochondrial DNA is used for maternal ancestry. The primary reasons being: (1) these sources for DNA are not subject to the normal variability’s found in inheritance; (2) Y-chromosome DNA is passed only from the father; and (3) mitochondrial DNA is passed only from the mother. Using these DNA sources, both paternal and maternal ancestry can be traced. In either case, the only changes that occur over time are rare mutations. This is the basis for the Genographic Project that has defined the world-wide migrations of the human family. See www.genographic.com for more on this fascinating story. Therefore, the results below also pertain to all the male Creegans in the direct line to Michael Creegan (b. c. 1790 in Ireland).


William Creegan submitted a DNA sample to the Genographic Project in August 2006 for a 12 marker analysis. The results indicated the Y-chromosome DNA belongs to the R1b1 Haplogroup. Haplogroups represent the DNA patterns that are used to divide up populations into their ancestral origins based on the accumulation of mutation markers over time. R1b1 is the most common haplogroup in European populations including Ireland. It is believed to have expanded throughout Europe as humans re-colonized after the last glacial maximum 10-12 thousand years ago.


This is where things get interesting - when the results were received, it was indicated that there was a “deep clade” test available for R1b1 to provide additional information about our ancestry. The test was requested.


The results were astonishing. We belong to the R1b1c7 subclade which has become known as the Northwest Irish Variety of R1b1c. R1b1c7 is concentrated in Sligo and Donegal areas. Also, researchers at Trinity College Dublin feel this subclade is associated with the Ui Neill kings of Northern Ireland who descended from the fifth century warlord, Niall of the Nine Hostages.


To help clarify what this means, the following excerpts from various sources were paraphrased:


Family names associated with the cluster were almost entirely Irish or Scottish. It is most concentrated in Sligo and northernmost Donegal (nearly 20 percent of the population) and nearby counties to the south and west (five to 10 percent). It is also found in Lowland Scotland and the Western Isles at a percentage that is hard to calculate but may also be in the five to 10 percent range.

Based on correlations with modern surnames, clan origins, and geographical concentration, Moore and McEvoy propose that this haplotype should be associated with descendants of the Ui Neill kings of medieval Ireland, and specifically descendants of the semi-legendary fifth-century king Niall of the Nine Hostages. The reproductive advantage conferred by political and military leadership is considered to have fostered the expansion of this pattern, which is found in up to one fifth of tested males in portions of NW Ireland today. The pattern is scarce in Southern Ireland. Descent from Niall is quite possible and even likely for much of the Irish population in whom this pattern is found, but it is not necessarily the case that all who manifest this variety are direct descendants of Niall.

A recent book by Stephen Oppenheimer, “The Origins of the British,” (Carroll & Graf, New York, 2006) reports that the first post-glacial (or almost post-glacial) inhabitants of what we now consider Ireland migrated there from the area called Galicia in NW Iberia about 5,000 years ago. They came up the narrow ice-free coast of the continental mass that would become the British Isles after the majority of the ice melted. Though he does not use the clade label R1b1c7, it is clear from context that Oppenheimer believes these “first Irish” included the R1b1c7 cluster or the individuals from whom that cluster would develop. If he is correct then the roots of our subclade go back far earlier than the family of Niall of the Nine Hostages.

So it appears our ancestors may have been among the “first Irish” inhabitants!
The r1b1c7 designation also clarifies and gives substantial
 weight to the origin of the Creegan name. The DNA results
 and our surname both support that we are descended from
 Niall of the Nine Hostages (and specifically his son Eoghan),
 who were from Donegal and Sligo. Some of our relatives may
 even have been wealthy merchants!


Now, let’s get back to the DNA analysis results. It quickly became clear that 12 markers were not enough. Any matches would be too vague to make an assessment about relationships. Therefore, a 37 marker analysis was requested. The results were provided in two steps - 25 markers and then 37 markers. There were several exact matches at the 25 marker level and none at the 37 marker level, the closest being 34/37. This is not a big surprise – if we had exact matches at 37 markers, we can see from the chart below that there would be a 95% probability that the person would be related within the past 7 generations (7 x 25 years) regardless of the surnames.  If the surnames were the same, the probability would jump to 99% for all the MRCA’s shown in the chart. There are currently at least 9 contacts in the database with a genetic distance of 3 from ours and of the 4 that I can identify, 3 are from Scotland and one is unknown. Go figure.


There are a number of tools available to participants and they show, for us, that there are most likely no current participants in the project with a MCRA closer than 13 generations back (about 325 years) – that would be around 1681 when we last shared a brew at the local pub, probably in County Sligo. It is interesting to note that the Sligo and Roscommon areas are still populated with more Creegans than other areas of Ireland (unofficial survey). The detailed report may be of interest to you (pdf file).



Probability for Most Recent Common Ancestor (MRCA) (from the Genographic web site).

Number of matching markers

50% probability
that the MRCA was no longer than this number of generations

90% probability
that the MRCA was no longer than this number of generations

95% probability
that the MRCA was no longer than this number of generations

10 of 10




11 of 12




12 of 12




23 of 25




24 of 25




25 of 25




35 of 37




36 of 37




37 of 37

2 to 3



65 of 67




66 of 67




67 of 67








With time and a little Irish luck, the Genographic database will help us discover more about our ancestors.