The O'Rourke y-DNA Results

DNA strand

See also the series of articles beginning with First Thoughts on the O'Rourke Autosomal DNA.

We were tested on 67 markers the first time, and on 37 markers the second. Here are the facts. I don't know what conclusions to draw, but I will give it a try afterward.

My two cousins' y-DNA matched each other. So we know that there wasn't a testing error on the first sample.

There are almost 6,000 results in the All Ireland Surnames project at familyTreeDNA including 14 O'Rourkes. We don't match any of them on even 12 markers.

None of those 6,000 were for anyone named Brennan, Sloan, O'Rourke, Colgan, Cunningham, Rodgers, or Fearon, from Killowen or Kilkeel. Those are some common names in the area that I could remember.
We don't match anyone at all on familyTreeDNA for 25, 37, or 67 markers, even allowing for 7 mutations difference.

We match two men named Mr. Ebrahem and Mr. Abbas on 12 markers, but, again, no Irishmen on 12 markers.

Finally, we know from the earlier autosomal DNA results that our O'Rourke family must have been in Ballintur, County Down, by at least 1779 when James Rourke was born, because we share a lot of autosomal DNA with his wife's family, the Colgans.


  1. The O'Rourke DNA and the research are reliable as far back as we have traced them. In other words, my cousins' DNA is the same as James Rourke's would have been in 1779. Everything lines up as far as it goes.

2. We share a common ancestor with the two men, Mr Ebrahem and Mr Abbas, but it has to be well back into the Middle Ages, or else we would have matched them on more markers. Like before 1500 or so and probably way before.


The weird part is that we don't share a common ancestor, even that far back, with anyone in the All Ireland Surnames project, or anyone else at all for that matter. You would think that in the course of 1,000 years or so someone would have "strayed" from their wife or wives and fathered a son who grew up with a different name, or that someone would have changed surnames for one reason or other.

For example, our Hamilton DNA matched a descendant of a man named Fields on all 37 markers. His descendants always had been told that he was a Hamilton by birth, but was raised by the Fields. And so it must have been.

Another example: my wife's grandmother's family name is Jenkins. But if they had their y-DNA tested it wouldn't match any Jenkins at all, because about 1850 a man named Samuel Crimm came to Boston from New Jersey and started calling himself Charles Jenkins. A police matter? probably, but now they are Jenkins.

So what about the link to the Arabs?

Well my only two guesses are either:

1) someone named O'Rourke left Ireland, maybe at the Flight of the Earls or much earlier, for one reason or other, and ended up in the Middle East. He settled down and adopted a local surname.

2) Sometime in the Middle Ages a merchant from the Middle East came up the Atlantic Coast, found Carlingford Lough to his liking, and decided to stay.

I'm actually leaning toward the second, because if someone left Ireland wouldn't he have left some genetic trace behind him? Or wouldn't his father, his brother, or his male cousins have stayed and had descendants? Or did the whole family pack up and leave for the Mediterranean?

Another conclusion

Finally, another conclusion is more emotional. It is based on 1) no matches, 2) no other test from Killowen or Kilkeel, and 3) personal experience. That conclusion is that the people from that area were so isolated, between the Mourne Mountains and the sea, that they cared less about the rest of the island's inhabitants until events forced them to do so.

And maybe that was because they weren't related to any of them.

Continued in The O'Rourke y-DNA -- an update, November 2015.