The O'mahonys
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The O’Mahonys A multi-disciplinary approach to a genetic surname study Cai Maver, [email protected], 2017 May 30 Abstract The O’Mahonys are an Irish family who claim descent from Mahon, son of Cian, who lived in the 11th century AD and became chief of the Eóganacht Raithlind tribe of south Munster. The O’Mahony family is conspicuous in the historical record, with many named septs associated with specific lands in counties Cork and Kerry. This paper examines the genetic and geographic data of participants in the O’Mahony Surname Project to determine if any of the genetically distinct families bearing the surname can be connected to any particular person, sept, or lineage in the historical record. In doing so, this paper attempts to suggest which haplogroup the progenitor of the clan, Mahon, might have belonged to. Background The Historical Record The O’Mahonys are reputedly descendants of Corc, King of Munster, who lived in the fifth century AD (O’Hart, 1892; O’Mahony, 1913). Aside from the O’Mahonys, Corc is said to be the ancestor of all of the Eoghanacht clans who would become families such as the O’Sullivans, the MacCarthys, the O’Donoghues and the Stuarts of Scotland. However, we can’t assume that an ancestor’s surname indicates direct, patrilineal descent from a single common ancestor – in this early age, families might adopt the name of a famous ancestor regardless of whether that ancestor was on the mother’s or father’s side (O’Mahony, 1913). In examining the O’Mahonys, or any surname group, it is necessary to limit the investigation to the time period when surnames were passed down in a patrilineal manner. The O’Mahonys are named after Mahon (Mathghamhna in Irish), chief of the Eóganacht Raithlind tribe who died in 1038AD (O’Mahony, 1913). Mahon was the son of Cian, who lead Brian Boru’s second division at the Battle of Clontarf, and Sadhbh, a daughter of Brian Boru (O’Mahony, 1913). In this time period, Mahon was a given name, and we should expect that there will be other lineages who are descendants of a man named Mahon (thus MacMahon or O’Mahony), but who are not descendants of Mahon son of Cian (Mahon mac Cian). For example, Sadhbh’s uncle, Brian’s elder brother, was also named Mahon and he is said to be the ancestor of the MacMahon’s (O’Hart, 1892). Cian’s 4x great-grandson Donogh na Himerce Tiomcuil O’Mahony is, according to the histories, the most recent common ancestor for all the O’Mahonys who descend from Cian (O’Mahony, 1913). Donogh was the last chief of the united O’Mahonys; upon his death in 1212AD, his son Diarmuid Mor O’Mahony became the chief of the western O’Mahonys based around the Mizen Peninsula while his son Concobar became chief of the O’Mahonys of Kinelmeky. Septs – named lineages of the family descended from a significant ancestor and usually associated with a geographic area – descend from either Diarmuid Mor The O’Mahonys: A multi-disciplinary approach to a genetic surname study 2 or Concobar, and the lands occupied by these septs may reveal clues regarding from which branch of the family they descend. The descendants of Diarmuid Mor and Concobar are fairly well documented and outlined in Rev. John O’Mahony’s comprehensive History of the O’Mahony Septs of Kinelmeky and Ivagha (1913), but the sons of many of the minor septs are not often given in the sources used by O’Mahony. The history on most lines goes to the 1600s when many of the O’Mahony lands were lost and many of the clan left for the continent. There is a roughly 100 year period from the late 1600s to the early 1800s – corresponding with the time of the Catholic Penal Laws in Ireland – when there are very few records of the family. Like many families of Irish heritage, today’s O’Mahonys are generally able to trace their ancestors back to the 1800s, though often with great difficulty. The 19th century Irish diaspora spread the O’Mahony kinsmen around the globe, and not all are able to determine where in Ireland their O’Mahony ancestors came from. We turn to genetics to try and bridge the gap from our modern family tree back to that of Mahon mac Cian. The Genetic Record The O’Mahony Surname Project (2017) has been collecting and organizing genetic data from descendants of many O’Mahony families (and families with variants of the surname) since 2003, and much of that data has been published online. Nearly all of the members in the O’Mahony Surname Project descend from a common paternal ancestor by virtue of the fact that they share the L21 Single Nucleotide Polymorphism (SNP), either confirmed through SNP testing or by haplogroup prediction using Short Tandem Repeat (STR) markers. However, that common ancestor is also shared by more than 60% of all Irishmen and that common ancestor lived more than 4000 years ago (Hay, 2017) – this common ancestor is not relevant to our genealogical goal of identifying genetic descendants of Mahon who lived around 1000 years ago. Likewise, several of the haplogroups found in the O’Mahony Surname Project share a common ancestor in the haplogroup founder, but that founder will have lived much more than 1000 years ago, too long ago to matter in this investigation. Considering that the O’Mahonys descend from Mahon mac Cian who lived from about 980AD to 1038AD, we should look for haplogroups that would have been formed about 1000 years ago. Anything older than that should be considered to be not genealogically related in the direct paternal line. Using the SNP and STR based estimates for the Time to Most Recent Common Ancestor (TMRCA) within each haplogroup, the participants in the O’Mahony Surname Project can be divided into groups that may descend from an ancestor 1000 years before the present or earlier. These clusters can then be examined for correlations with the O’Mahony historical record and with the geographic locations of septs of the clan. Geography Being the chiefs of the Eóganacht Raithlind, the O’Mahony lands in the 11th century were equivalent to the Diocese of Cork: “The Diocese of Cork, according to the Synod of Rathbreasil, which was held about 70 or 80 years after Mahon's death, extending ‘from Cork to Carn Ui Neid, and from the Abhain Mor (Blackwater) to the southern sea.’” (O’Mahony, 1913) The O’Mahonys: A multi-disciplinary approach to a genetic surname study 3 The next several centuries, however, would see the O’Mahony lands shrink under the pressure from the Norman invaders and the MacCarthys. The following summary of the O’Mahony septs and their lands is drawn entirely from Rev. John O’Mahony’s (1913) work. In the middle of the 13th century, following the murder of Muirchertach, chief of the O’Mahonys, at the hands of Donal Gott MacCarthy in 1232, the O’Mahonys divided their lands between Muirchertach’s brothers. The elder brother, Diarmid Mor O’Mahony, became the chief of the western O’Mahonys based on the Mizen Head while Concobar O’Mahony became the chief of the eastern O’Mahonys Carbery with their seat at Castle Mahon near Bandon. The lands between these eastern and western halves was claimed by Donal Gott MacCarthy who made his son Donal Maol MacCarthy first Prince of Carbery. The following generations of O’Mahonys would form several septs based on subdivisions of the O’Mahony lands. Clan Fineen na Ceitherne is the earliest sept of the western O’Mahonys, named for Fineen, the eldest son of Muirchertach O’Mahony. He was given lands in west Muskerry and Moviddy parish; one branch of his descendants in the same lands became the O’Mahony Ruadh named after Fineen’s grandson Donogh Ruadh O’Mahony. Adjacent to their lands, in the parishes of Kilmurray and Kilmichael were the Clan Conogher, descendants of Conogher, grandson of Maghnus O’Mahony of the Carbery branch. To the west of Clan Conogher in the parish of Kilmichael were the lfflonloe sept, descendants of Tadhg an Oir O’Mahony, brother of Diarmuid Mor O’Mahony II of the western O’Mahonys. This branch was also known as O’Mahony an Oir (Irish for “the golden”) and would have septs of its own: O’Mahony an Crochair for the descendants of Concobar an Crochair O’Mahony and O’Mahony Buidhe after Diarmuid Buidhe O’Mahony. When Diarmuid Mor O’Mahony II died in 1327, his eldest son Fineen became 5th chief of the western O’Mahonys. Fineen chose not to honor his father’s arrangement that his brothers Donal and Diarmuid should inherit lands and castles on the Mizen peninsula. Donal and Diarmuid left their homeland and joined the MacCarthys, from whom Donal obtained lands in Kilnaglory and Diarmuid obtained lands in County Kerry. The descendants of Donal became the O’Mahony of Kilnaglory sept and Diarmuid’s descendants became the large sept “O'Mahony of the Sliocht Dermod Og” associated with several locations in county Kerry. Regrettably, nearly all of the O’Mahony lands were confiscated by the English and redistributed to adventurers or Irish lords loyal to England following the rebellion of 1641. The Down Survey of Ireland was undertaken at the direction of Oliver Cromwell in the years 1656-1658 to map the lands owned by Catholics to be forfeited (Trinity College Dublin, 2013). The survey includes many of the O’Mahony land owners of the late 1650s and is a valuable resource for determining where various branches of the O’Mahonys lived prior to the loss of so many of their lands.