As many as 3 million men worldwide might be directly descended from a single Irish warlord named Niall of the Nine Hostages who was the High King at Tara from 379 to 405.
In February 2006, researchers at Trinity College in Dublin released a paper that studied that Y chromosome signature of men throughout Ireland. They found that 8% of men sampled had the same Y chromosome, with a cluster in the northwest where fully 21% of men carried the signature chromosome (which fell into Haplogroup R1b1c7). The article appeared in The American Journal of Human Genetics and was titled “A Y-Chromosome Signature of Hegemony in Gaelic Ireland.”
The researchers looked at 17 STR markers on Irish Y chromosomes to determine the relatedness of samples they had obtained. They found that there was a strong association between the most common signature and surnames that were related to the most significant dynasty of early medieval Ireland – the Uí Néill. Some of the surnames included (O’)Gallacher, Boyle, O Doherty, O’Connor, Cannon, Bradley, O’Reilly, Flynn, (Mc)Kee, Devlin, Donnelly, Egan, Gormley, Hynes, McCaul, McGovern, McLoughlin, McManus, McMenamin, Molloy, O’Kane, O’Rourke and Quinn (list from Oxford Ancestors). Of course there were no surnames at the time of the earliest Uí Néill dynasty, but when the Irish took surnames around 1,000 A.D., many chose names that were associated with Uí Néill dynasties.
This association suggests that men with the signature Y chromosome are descended from the founder of the dynasty Uí Néill, Niall of the Nine Hostages. Niall of the Nine Hostages, who was the High King at Tara from 379 to 405, founded the dynasty Uí Néill, which ruled until the 11th century. According to the legend, Niall had 12 sons, many of which were rulers after Niall’s death.
The biggest caveat of this research is that without testing DNA from Niall’s remains, it is impossible to say with 100% certainty that Niall is the ancestor (and some argue that there never was a real Niall). For instance, Mrs. Niall could have only reproduced with the friendly neighbor, or a large fraction of the men with the signature Y chromosome could be descended from Niall’s promiscuous uncle George (I don’t know if there was an uncle, or if his name was George – it’s just an example).
As the authors of the study pointed out:
“The fact that about one in five males sampled in northwestern Ireland is likely a patrilineal descendent of a single early medieval ancestor is a powerful illustration of the potential link between prolificacy and power and of how Y-chromosome phylogeography can be influenced by social selection.”
Not surprisingly, the signature Y chromosome has also spread around the world, suggesting that there may be as many as 3 million people who carry it. Using international DNA databases, the chromosome was found in roughly 1 in 10 men in Scotland, and in about 2% of European-American New Yorkers.
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