Alright so my Haplogroup on 23andme used to R-L21 and has recently been updated to R-S660 of which I understand is a more specific subclade of the former. So, what country is R-S660 predominant in and what does it say about my paternal ancestry? This is important to me because I cannot trace my father's line back to the old country. My father's surname is one of the names that comes from old Gaelic Mac Aoha but I have no idea if his ancestors were Irish, Scottish, or Ulster Scots. The situation is confusing because while its a surname associated with the native Irish its also found in Scotland, and according to some genealogies of other unrelated families with the same name among the protestants of Ulster as well. I live in the American South which was heavily populated with Ulster Scots but also some Scottish and Irish so I can't really tell anything by my surname. Help would be appreciated and thank you in advance.
That's a bit tricky to disentangle, because these separate identities (
Irish, Ulster Scots and Scottish) indicate you want to know the ethnic and social identity of people after the Protestant Revolution and before they went to the US - and the 3 possibilities are actually extremely close to each other historically, so some overlapping is virtually inevitable and you can't discard the possibility that even if your haplogroup is more common in some of those groups than in the others you can still descend from someone who belonged to that smaller minority in the other ethnic group, especially because Y-DNA haplogroup is much easier to be thoroughly "changed" than your autosomal ancestry. But the subclade R-S660 or R1b-L21 is, according to YFull YTree, 1850 years old and has a TMRCA of ~1800 years. That's more than enough time for the haplogroup to travel to the other side of the narrow strip of ocean dividing Ireland from Scotland or Wales. Besides, a relevant proportion of Scottish people have Irish ancestry, Scottish Gaelic being a testament to that close relation (that Celtic language in Scotland almost certainly did not come directly from Pictish or Brittonic people in Britain itself). Then Ulster Scots, who had come from Scotland, reversed the flow of migration towards Ireland, and there it's not possible to say there wasn't any mixing whatsoever with Irish people and no conversion to their ethnoreligious identity throughout the centuries - apart from the fact that mixing with Irish people may have happened centuries earlier, when many Irish came to live in Scotland, or even so many years ago that there were only Celts in the British Isles and not even a shadow of a Scottish identity existed yet.
As I said, I think it's complicated. The R-L21 and S-660 subclades indicate that you must have some Irish (the clear majority of people with the DF109/S660 subclade live in Ireland) or more broadly Insular Celtic ancestry (maybe in its earliest origins associated more with Goidelic Celtic languages instead of Brittonic ones?). But you may well descend more directly, in a more modern perspective (i.e. the last 300 years), from an Ulster Scots or a Scottish man, but one that had had some Celtic or more specifically Irish ancestors centuries earlier.
Finally, remember that your Y-DNA does not define most of your ancestry. It just tells you something interesting about
one of your many paternal ancestors, the one who had an unbroken line of male descendants until you were born. It's theoretically totally possible that the overwhelming majority of your ancestry does not even come from the same population that your male forebear that lent his Y-DNA haplogroup to you belonged to.
