The Genetic Genealogy of the peoples of Ireland and Great Britain had been the same from the end of the last Ice Age until the Anglo-Saxon period. Even today, 'The People of the British Isles' DNA study found Anglo-Saxon DNA generally in the southeast half of England with a maximum of 38% in the far southeast nearest the Continent. Recent DNA work has shown that there were three waves of migration into western Europe after the last Ice Age. There were people from the earlier time called the Paleolithic (Old Stone Age), but these lived in southern Europe in the Pyrenees area, Italy, and the Balkans.
The waves began as the ice receded throughout Europe and the first wave into the Isles began around 8,000 BC. (There are remains of a hut from about 7000 BC at Mount Sandel, County Derry.) Mount Sandel, a Mesolithic Campsite. These Mesolithic (Middle Stone Age) people are called Hunter Gatherers and were not yet settled in a single permanent place. It was Western Hunter Gatherers (WHG) who made their way to Mount Sandel. (There are different labels for various related HG group across Eurasia.)
The first work that was important for Irish Genetic Genealogy was done in 2005/2006 by Brian McEvoy of Trinity College Dublin. He used STR data from a sample of a few hundred surnames drawn from the phonebook throughout Ireland. Among the names were Haughey and Dunleavy. Haughey can be a phonetic rendition of Ó hEochaidh. The 1659 spelling of O'Hoy in Pendar's work was from an English viewpoint. In Ireland, Hoy is now Hoey and pronounced closer to Haughey. The last five kings of the Dál Fiatach were brothers who changed their surname from Hoey to MacDunleavy after Dunleavy Ó hEochaidh who was a king who died in 1091. After the Normans drove the Dál Fiatach out of County Down, the MacDunleavy were known to have become the hereditary physicians to the Cenél Chonaill in southwest Tir Chonaill (Donegal) near their base in Donegal Town.
From Griffith's Valuation from 1856 in Donegal, we find the almost all Haughey clustered in far southwest Donegal near Glencolumbkille and the MacDunleavy in the same area. The graphic above is taken from McEvoy's work for the Haighey/MacDunleavy and compares a living Hoy at the top with McEvoy's results. He identified several markers called haplotypes among the STR data. Among them were R1b, M222 (subgroup of the former), and 'I' which is likely pre-Bell-Beaker and associated with a subgroup of the Uladh and the Maginness and McCartan lines in west County Down. We can see the closeness of the living Hoy with the M222 men.
The last 6 kings of the Dál Fiatach were a man Cú Uladh and his 5 sons who ruled from 1131 to about 1200 A.D. Byrne says that to distinguish themselves from the larger family, in 1137 they took a new surname MacDunleavy. They are recorded as moving to Donegal they became hereditary physicans to the Cenél Chonaill kings, the O'Donnells in order to maintain their honor price and nemed (noble) status under Féineachas ('Brehon Law'). See below for Donegal.
The majority of the family moved to nearby Airgíalla (Oriel), Louth/Monaghan under the protection of the Ua Cearbhaill (O'Carroll) king whose mother was Ana O'hEochaidh. The main branch of the Sloinne Ó hEochaidh moved to Louth/Monaghan after 1200 AD.
Donegal is entirely dominated by non-A725 sub-trees of M222 with only five A725 in the county and those in the same small area of SW Donegal outlined in the 1st row, 3rd column picture in this link. The SAPP process has identified a branch of A725 which contains these five men as well as five others. A branch of the Sloinne Ó hEochaidh moved to Donegal after 1200 AD.
- Byrne, Francis John (2001), Irish Kings and High-Kings, Dublin: Four Courts Press, ISBN 978-1-85182-196-9
- Brian Patrick McEvoy, First published 2005, Genetic investigation of Irish ancestry and surname history
- James McNish, First published 22 February 2018, "The Beaker people: a new population for ancient Britain", The beaker-people a new population for ancient Britain
- Lara M. Cassidy et al, First published December 28, 2015, "Neolithic and Bronze Age migration to Ireland and establishment of the insular Atlantic genome", Cassidy et al
- Davidski - Eurogenes Blog, Wednesday, January 16, 2019, "Single Grave > Bell Beakers", Single Grave Bell-beakers