The scientists, from Trinity College Dublin, have discovered that as many as one in 12 Irish men could be descended from Niall of the Nine Hostages, a 5th century warlord who headed the most powerful dynasty in ancient Ireland.

His genetic legacy is almost as impressive as that of Genghis Khan, the Mongol emperor who conquered most of Asia in the 13th century and has nearly 16 million descendants, Dan Bradley, who supervised the research, said.

"It's another link between profligacy and power," Dr Bradley told Reuters. "We're the first generation on the planet where if you're successful you don't [always] have more children."

The research was carried out by PhD student Laoise Moore at the Smurfit institute of genetics at Trinity. Ms Moore, testing the Y chromosome which is passed on from fathers to sons, examined DNA from 800 males across Ireland.

The results - published in the American Journal of Human Genetics - showed the highest concentration of related males in north-west Ireland, where one in five males had the same Y chromosome.

A similar study in central Asia had found 8% of men with the same Y chromosome. Subsequent studies found they shared the same chromosome as the dynasty linked to Genghis Khan.