My dad knows nothing about our ancestors so I thought some family history would be perfect for a father’s day present. After a quick scan of genealogy sites I discovered that according to folklore the Ó Dálaigh (Daly) clan were descendants of the 5th century warlord Niall of the Nine Hostages. This meant they were part of the Úi Néill (descendants of Niall), a lineage of high kings of Ireland. An excellent start to my quest but being more interested in science than trailing through the archives, I turned to genetics.

Research carried out in Trinity College in 2006 on Y-chromosome signature gave me a greater insight into the Úi Néill. Y-chromosomes were used to track paternal lineages as in medieval Ireland it was tradition to pass on title and land to sons both inside and outside marriage. Modern Irish surnames are evidence of this tradition: O (grandson of) and Mac (son of).

The DNA of Y-chromosomes was tested in 796 men from all areas of Ireland. The researchers were interested in a haplogroup R1b3 which is at its highest frequency in western parts of Ireland. My ancestral mystery was solved by a unique pattern of clues, SNPs (single nucleotide polymorphisms), which form the R1b3 haplogroup. In haplogroups, SNPs are changes in a single nucleotide of DNA in areas that do not directly affect gene function.

The researchers tested a region within this R1b3 haplogroup in the Irish men and found that 8.2% had a marker they found to be “Irish”, increasing in the northwest to 16.9%. Over hundreds of years parts of DNA which are not associated with gene function mutate which is called divergence. Because changes occur in such a small evolutionary time period, these parts of our DNA can be used to study our ancestry. They tested the “Irish” marker for divergence and found it was significantly reduced in men with surnames that are historically associated with Úi Néill. This shows there is an association between the “Irish” marker and the Úi Néill dynasty. My excitement about my Irish royal lineage is fading fast as it seems despite the image of exclusivity of royalty, this is very common.

So what explains the frequency of the descendants of Niall? We’ve all heard about the birds and the bees so it was appropriate this week when finches were used in a study into the inheritance of promiscuity. Finches, like humans, form monogamous lifetime partnerships. However, it was shown that some male finches had the urge to cheat which leads to them having more children. But here comes the surprise… the daughter’s of cheating male finches are more likely to have affairs than those of faithful males but this doesn’t give them any extra children. The scientists suggested that females cheat due to genetic variants passed on by their fathers which can enhance promiscuity. This means promiscuity can be inherited.

If this study transfers to humans and if Niall of the Nine Hostages was promiscuous, then he passed this trait on to his children. Throw in the appeal of warlords and high kings as partners and 1,700 years. The result: millions of modern Úi Néill around the world. So I, daughter of the grandson of Daly, could be linked with a history of centuries of promiscuity. Maybe my dad didn’t research our ancestors for good reason!

Moore, L., McEvoy, B., Cape, E., Simms, K., & Bradley, D. (2006). A Y-Chromosome Signature of Hegemony in Gaelic Ireland The American Journal of Human Genetics, 78 (2), 334-338 DOI: 10.1086/500055

Forstmeier W, Martin K, Bolund E, Schielzeth H, & Kempenaers B (2011). Female extrapair mating behavior can evolve via indirect selection on males. Proceedings of the National Academy of Sciences of the United States of America, 108 (26), 10608-13 PMID: 21670288