To explain how DNA can shed light on one’s Irish ancestry requires a brief reminder of a crucial biological event. This event is the moment of conception, the point at which we receive half of our DNA in the form of chromosomes from each parent. A complete complement of genetic material essential for human life consists of 23 pairs of chromosomes, one half of this pair is delivered via a father’s sperm to the other half found in the mothers egg.  One of these pairs of chromosomes known as the XY pair determines the gender of a child, this is because a single sperm can only deliver either an X or Y chromosome, if a Y carrying sperm fertilises the X carrying egg (a mothers egg only ever carries an X chromosome) this leads to an XY pair and a baby boy, while an egg fertilised by an X carrying sperm results in an XX pair and a baby girl.

It is the man therefore that determines the sex of a child by the transfer of either the X or Y chromosome. This means that the Y chromosome has been passed from father to son since the dawn of time. It is the only bit of DNA that is transferred continuously from father to son in this manner and because all DNA mutates over time, the Y chromosome that a son receives from his father, differs slightly to his fathers, which in turn differs further from his grandfathers. More importantly for family history enthusiasts, scientists can examine and compare specific parts of the Y chromosome from multiple male individuals and estimate how long ago a shared ancestor lived. This finding has led to the emergence of commercial companies that examine ancestral origins using the Y chromosome. The DNA test typically looks at 37 individual pieces of the Y chromosome referred to as markers. The results of this test tell you how many markers you share with an individual who has also been tested. For example individuals who share recent ancestry will match at 37/37 markers, whereas more distant shared ancestry will be reflected in 35/37 and 33/37 markers.

However, for anyone who has ever taken a commercial Y chromosome DNA test they will have been perplexed by the number of individuals with different surnames with whom they share ancestry. How can this be? The answer is surprisingly simple; over 1,000 years ago, when surnames became common your Irish ancestor lived in a particular area where he picked his particular surname. He lived close to others, some of whom he was related to, but who crucially chose other surnames. Hence a group of related individuals gave rise to a small number of surnames that arose in a specific location within Ireland. Jump forward 1,000 years and there will be many descendants of that small group, some of whom will today undergo ancestral DNA testing. In essence what you see with your surname matches from commercial Y chromosome DNA testing is a snapshot of your ancestor’s neighbours from 1,000 years ago! Since Irish surnames can still be found concentrated in the areas where the first arose one can examine surname distribution maps and see where in Ireland those surnames originate and reveal a ‘Genetic Homeland.’

The Genetic Homeland is the location where one’s ancestors lived for 100’s if not 1’000’s of years, it is the area where he first took his surname, where he left his mark in the place names and castles of that area, and in the DNA of its current inhabitants. For example, my surname is Bowes, upon Y chromosome 37 marker DNA testing I matched many individuals called Carroll, Dooley, and Bowe. Surname distribution mapping demonstrates that all of these surnames are concentrated in County Laois in Ireland (Figure 1). By examining the place names in County Laois I found evidence of my ancestors long association with that area in Bowe’s crossroads, Toberboe (Bowe’s well), and Aghaboe (Bowe’s field), but also places associated with my genetic relatives; Dooley’s crossroads, Killadooley (Dooley’s church), and Ballycarroll (Carroll’s town). But the truly enormous power of DNA technology lies in the fact that once you have discovered your own personal Genetic Homeland you can prove it by DNA testing individuals with your surname from the pinpointed area. In the case of the Irish Bowes DNA study, a number of individuals with the Bowe/Bowes surname were recruited from County Laois and tested, and the results confirmed that we shared a common ancestor (the first to call himself Bowe’s, the Bowe’s Adam so to speak). It is truly remarkable to think that a simple swab of cheek cells can prove that my Irish ancestors lived in County Laois over 1,000 years ago.

The process works remarkably well specifically because of our unique Irish heritage; Ireland was the first country in Europe to adopt Surnames, those Irish surnames are often instantly recognisable beginning with Mc’ or O’ and are a genealogical record in themselves meaning son of, or grandson of respectively. Our medieval Clan system, where science has demonstrated that each of the estimated 1,800 Irish Clans had potentially a single founding ancestor, that’s 1,800 Adams from whom one can demonstrate ancestry through commercial DNA testing. Then there is the age old Irish obsession with land, one just has to look at Jim Sheridan’s film ‘The Field’ starring Richard Harris to see how much land features in the Irish psyche, it is an obsession as evident now more than ever in our recent property crash. And finally our place names that typically reflect the ancient inhabitants of an area.

So what are the implications? Well for the first time ever all of the estimated 80 million people worldwide with Irish ancestry can use their DNA to pinpoint where in Ireland their ancestors lived and where their distant relatives still live! If your ancestor lived there 1000 years ago, they most likely lived there 100, 200, 300, or 400 years ago when they left these shores and spread all over the world. In fact your DNA can pinpoint an area where the genealogical paper trail will end, or should that be where the paper trail begins? However when I discovered how to pinpoint a Genetic Homeland I realised that the resources that one would need to attempt this process were not available. The Irish Origenes website was therefore created to fill that need. The website contains background information, databases, and a range of novel Irish maps that will help people to understand, interpret, and to put their DNA results into a historical context.

This article was published in Irish Roots Magazine http://www.irishrootsmedia.com/issue/93