Up to three million men around the world could be descended from a prolific medieval Irish king, according to a new genetic study.

It suggests that the 5th-century warlord known as “Niall of the Nine Hostages” may be the ancestor of about one in 12 Irishmen, say researchers at Trinity College Dublin, Ireland. Niall established a dynasty of powerful chieftains that dominated the island for six centuries.

In a study of the Y chromosome – which is only passed down through the male line – scientists found a hotspot in northwest Ireland where 21.5% carry Niall’s genetic fingerprint, says Brian McEvoy, one of the team at Trinity. This was the main powerbase of the Ui Neills, which literally translated means “descendants of Niall”.

McEvoy says the Y chromosome appeared to trace back to one person.


“There are certain surnames that seem to have come from Ui Neill. We studied if there was any association between those surnames and the genetic profile. It is his (Niall’s) family.”

Enduring dynasty

The study says that Niall “resided at the cusp of mythology and history but our results do seem to confirm the existence of a single early medieval progenitor to the most powerful and enduring Irish dynasty”.

The results also lend support to surviving genealogical and oral traditions of Gaelic Ireland and are a “powerful illustration of the potential link between prolificacy and power”.

The study says the chromosome has also been found in 16.7% of men in western and central Scotland and has turned up in multiple North American population samples, including in 2% of European-American New Yorkers.

“Given historically high rates of Irish emigration to North America and other parts of the world, it seems likely that the number of descendants worldwide runs to perhaps two to three million males,” the study says.

Modern surnames

It compares the result with similar research that suggested that Mongol emperor Genghis Khan has 16 million descendants after conquering most of Asia in the 13th century.

Though medieval Ireland was Christian, divorce was allowed, people married earlier and concubinage was practised. Illegitimate sons were claimed and their rights protected by law.

“As in other polygynous societies, the siring of offspring was related to power and prestige.” The study points out that one of the O’Neill dynasty chieftains who died in 1423 had 18 sons with 10 different women and counted 59 grandsons in the male line.

Niall of the Nine Hostages, who became high king of Ireland, got his name from using the taking of hostages as a strategy for subjugating his opponent chieftains. He is known in folklore as a raider of the British and French coasts. Supposedly slain in the English Channel or in Scotland, his descendants were the most powerful rulers of Ireland until the 11th century.

Modern surnames tracing their ancestry to Niall include (O’)Neill, (O’)Gallagher, (O’)Boyle, (O’)Doherty, O’Donnell, Connor, Cannon, Bradley, O’Reilly, Flynn, (Mc)Kee, Campbell, Devlin, Donnelly, Egan, Gormley, Hynes, McCaul, McGovern, McLoughlin, McManus, McMenamin, Molloy, O’Kane, O’Rourke and Quinn.

Journal reference: American Journal of Human Genetics (February issue)