Medieval Irish genealogies are the oldest in Europe, stretching back over 2,000 years. These were transmitted orally (prior to the introduction of the written record) so are likely to be prone to inaccuracies prior to about 600 A.D. The first compilation of written records is believed to date from the mid-700s. Various versions of the medieval genealogies exist, and inconsistencies in these versions indicate further inaccuracies. Some of these inconsistencies appear to have been innocent transcription errors, whilst others may have been due to deliberate falsifications for social prestige or political gain. (1)
These known examples of inaccuracies have cast doubt on the veracity of the medieval genealogies as a whole, and this has been the subject of ongoing debate since the resurgence of interest in Irish heritage with the Gaelic Revival of the 1800s.
When FamilyTreeDNA made commercial Y-DNA testing available to the general public over 20 years ago, not only had they introduced a new tool for genealogical research, but they created the infrastructure that allowed genetic genealogy to emerge as a citizen science. Y-DNA has since evolved into an incredibly powerful tool for the study of surnames, and has the potential to shine new light on many old questions about these ancient Irish genealogies.
A new scientific article assesses what Y-DNA tells us about the medieval genealogies of the Uí Briúin (pronounced ee brew-in) dynasty of northwest Ireland. (2) The authors are Maurice Gleeson, Kyle DePew and Bart Jaski. Maurice and Kyle authored this current blog post and are project administrators of various FamilyTreeDNA Group Projects. Bart is one of the leading academic experts on Irish medieval genealogies and was one of our guest speakers at Genetic Genealogy Ireland 2019, which was kindly sponsored by FamilyTreeDNA. (You can see his presentation here.)
Back in 2019, Bart suggested that we should explore the link between the royal lineages of the O’Conor Don and the Mac Dermot of Moylurg, who reportedly shared a common ancestor in Tadg mac Cathail (pronounced tie-g mock caw-hill; born about 900 A.D.). The above article is the result of that work and is published in Peritia, the Journal of the Medieval Academy of Ireland.
The article is aimed primarily at Irish medieval historians and it is hoped that it will enlighten this community about the usefulness of Y-DNA as an additional research tool, as well as the work that is being carried out by genetic genealogists (volunteer Group Project Administrators) into Irish clan research. Increasing awareness in this way may help foster further collaboration and cross-fertilisation between the two disciplines.
The article was published in April 2024 and an e-version of the article became available for download in May 2024.
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| One of the many FTDNA-hosted DNA Projects associated with the Uí Briúin dynasty. See https://www.familytreedna.com/groups/breifne-clans/about |
Background: the precarious evolution of Irish surnames
Over the millennia, in a continuous process, Irish clans gave rise to subsequent clans. These descendant clans adopted specific surnames from about 900 A.D. onwards. Thus, any post-surname clans that descended from a specific pre-surname clan should be relatively closely related to each other genetically, and should therefore sit on adjacent branches of the Y-DNA Tree of Humankind (i.e., Y-haplotree), probably with the same overarching DNA marker.
But there are many important factors that influence if a particular surname has survived over the past 1,000 years or so, and if there are living descendants visible in the Y-DNA database today. Some of the most important of these factors include the following:
The Uí Briúin dynasty of northwest Ireland
Around 2014, Paul Duffy from Dublin (genetic genealogist and Group Project Administrator) noted that quite a few surnames associated with the Uí Briúin dynasty of northwest Ireland fell under the SNP marker A259 (a descendant of M222). (8) Since then, various FamilyTreeDNA Group Projects (run by volunteer Group Project Administrators) have explored this possible connection.
The specific surnames that are reported to be descended from the various branches of the Uí Briúin dynasty are summarized in the table below, divided into those associated with more powerful (major) clans (whose members became High Kings) and less powerful (minor) descendant clans. Each surname has a list of named ancestors (recorded in various versions of the medieval genealogies) that goes back to the reported progenitor of the Uí Briúin dynasty, namely Brión, supposed son of Eochaidh Muigh-Meadhóin (spelt in a variety of ways and pronounced roughly Yuck-ee Mwee Maydoyn).
Table 1: Some surnames associated with the various divisions of the Uí Briúin dynasty
Note that each branch of the Uí Briúin dynasty gave rise to multiple surnames. Sometimes the same surname arose independently in several branches (e.g., McTiernan, Flynn, McDonough).
So, in relation to the surnames above, there are two key questions:
Methods
In order to address these two key questions, we collated data from over 350 test takers who had undergone SNP testing (usually the Big Y test), who tested positive for A259, and whose data was publicly available from online Y-DNA haplotrees and the public results pages of various FamilyTreeDNA Group Projects, run by volunteer Group Project Administrators.
From this data, we constructed a Y-DNA haplotree (for those branches below A259) that included the surnames of the tested individuals. We called this the DAST (DNA-Associated Surnames Tree). The DAST is available to download as Appendix 2 (37 kB) from the figshare website here.
We also extracted data from three versions of the medieval genealogies (MacFirbis, O Hart, Jaski) to construct a CAST (Clan-Associated Surnames Tree) that summarized the various surnames that arose from the Uí Briúin dynasty, as well as their lines of ascent to their common ancestors. (9,10,11) The CAST is available to download as Appendix 1 (57 kB) from the figshare website here.
We then compared the CAST (the genealogical record) with the DAST (the genetic record), looking for consistencies and inconsistencies between the two datasets.
The three key questions we asked when comparing the genealogical and genetic records were as follows:
The Uí Briúin dynasty in the medieval genealogies
Eochaidh is reported to have had six sons in the earlier genealogies (probably the more accurate ones) and 24 sons in later genealogies (probably the more inaccurate ones). This is a good example of how the royal lineages “acquired” additional descendant lines as time went by, many being deliberately falsified and added to the genealogy for sociopolitical reasons.
Three of the sons of Brión’s great-great-grandson Fergus reportedly gave rise to prominent descendant lines which in turn gave rise to many kings and chiefs, some of whom gave rise to specific Irish surnames. These three branches were called the Uí Briúin Aí, Uí Briúin Seóla, and Uí Briúin Breifne, pronounced roughly Ay (as in hay), Show-la, and Breff-nuh. Figure 1 summarizes these three major branches and some of the surnames that arose from them (according to the medieval genealogies).
We will focus on these three major branches one by one. Bear in mind that this study was conducted in 2023 and took almost one year to be published, and because genetic genealogy is a fast-moving science, additional data has since become available that further supports many of the conclusions that are detailed below.
Uí Briúin Breifne
This clan ruled over a large territory stretching across what are now counties Leitrim and Cavan. The genealogical record reports that there are two early branches within this clan: one gave rise to the surnames McTiernan and McGovern, and the other gave rise to the surnames O’Rourke, O’Reilly, and Ford (with known variant McAna).
When comparing the genealogical record (CAST) with the genetic record (DAST), these names do indeed cluster close to each other on the Y-DNA haplotree. In the DAST, there is a cluster of four men called McTiernan on the branch characterized by the SNP marker FGC55184, and another cluster of McGovern men on FGC34296 (1 subject) and FGC59200 (7 subjects). These branches are offshoots of an over-arching branch characterized by the SNP marker A5902, which in turn is a descendant of A260, which is a descendant of A259. Furthermore, the branching structure in the genetic tree (DAST) is consistent with the branching structure in the genealogical tree (CAST), as illustrated in Figure 2 .
The MRCA (most recent common ancestor) for the McTiernan and McGovern branches (in the genealogies) is Máenach, who lived sometime between 600 and 760 A.D. (approximately). The genetic MRCA is A5902, and the TMRCA (time to most recent common ancestor) for this SNP has a central estimate of 709 A.D. (95% confidence interval 432-940 A.D.). This TMRCA estimate is consistent with the estimated birth year of Máenach … although with such a large confidence interval (i.e., just over 500 years) it would be difficult not to be! (Update May 2024: the current TMRCA estimate is now 664 CE, 95% CI 382-900. The range remains just over 500 years but the central estimate has decreased by 45 years.)
Incidentally, birth years are estimated from dates of death (and occasionally dates of birth) that are found in the ancient Irish annals (such as the Annals of the Four Masters). (12) These are a very useful accompaniment to the medieval genealogies and attest to the existence of many of the individuals named therein.
On this point, Y-DNA alone cannot confirm that a specific named individual actually existed. There must be supportive documentary evidence, and it is the totality of the evidence (documentary and genetic) that will determine the likelihood that a specific individual actually existed. Many of the more distant ancestors in the fabricated genealogies will be fake.
Another important point to make is that even though an MRCA passed on a particular DNA marker to all his descendants, this does not mean that that specific DNA marker arose in that specific MRCA. It may have arisen in his father, his grandfather, or further back along his direct male line. A specific research methodology exists for determining if a particular SNP marker arose in a specific named individual, and this entails testing validated descendants of two documented brothers. A good example of this involves the Stewart Kings of Scotland, where DNA testing identified a DNA marker (S781) that arose in in Sir John Stewart of Bonkyl (born in the mid-1200s). This DNA marker identifies his descendants (i.e. the Stewarts of Bonkyl) and distinguishes them from those of his brother James, 5th High Steward of Scotland, whose descendants include King Robert II, King Robert III, and King James I of Scotland. (13)
A similar story exists for the Uí Briúin Seóla. The major surnames in this part of the genealogies include McHugh, McDonough, and O’Flaherty (with variants Clardy and Clarida).
Figure 3 shows that these surnames cluster together in this portion of the Y-haplotree on branches characterized by the corresponding SNP markers FGC42414 (McHugh), FGC65259 (McDonough), and both FT367336 and YFS1251634 (O’Flaherty). The overarching SNP marker BY11725 is their most recent common genetic ancestor, which is a descendant of A260, which is a descendant of A259.
Instead, we are likely to be stuck with wide ranges (e.g., +/- 200 to 500 years) for the foreseeable future. In time, we might be able to narrow the range to +/- 50 years (for some well-tested branches) but that will only happen when a lot more people have undertaken the Big Y-700 test. Until then, TMRCA estimates will remain crude and will lack the precision desired by genealogists, which makes them especially prone to misinterpretation and confirmation bias.
The most recent common ancestor that the McHughs share with the McDonoughs and O’Flahertys in Cenn Fáelad mac Colgain. The corresponding genetic MRCA is BY11725 with a limited TMRCA estimate of some time in the 700s. This is reasonably close to the estimated birth year for Cenn Fáelad mac Colgain, which is about 620 A.D. (he was assassinated in 682). So again, there is no obvious inconsistency between the genealogical and the genetic record. (Update May 2024: the current TMRCA estimate for the newly-added SNP marker BY11725 is now 563 CE, 95% CI 231-837.)
Thus the clustering of reportedly related surnames, the branching structure below BY11725, and the TMRCA estimates in this part of the Y-DNA haplotree mirror what we see in the medieval genealogies for the Uí Briúin Seóla. However, the number of people involved in the analysis of the Uí Briúin Seóla (10) is much smaller than that for the analysis of the Uí Briúin Breifne (37) and additional SNP data is needed to help bolster these provisional conclusions.
Uí Briúin Aí
It is when we come to the Uí Briúin Aí that we start to see some important inconsistencies between the genealogical and genetic records.
This clan held sway over territories in what is now northern county Roscommon, extending into county Sligo. The major surnames in this part of the genealogies are Flanagan, O’Connor, McManus, McDermott (and the associated surnames McCormack & McDonough, and Morris).
Figure 4 shows eight men called McManus forming a cluster characterized by the SNP marker BY18179. A nearby cluster of three men called O’Connor sit on the adjacent branch, characterized by the SNP FT16709. Among this group is an immediate relative of the current chief of the O Conor Don clan. This royal line has a continuous lineage for over 30 generations (named ancestor by named ancestor) from the present day back to the medieval genealogies.
The MRCA for the McManus and O Conor Don clans is Tairdelbach Mór (roughly pronounced Ter-lock More), who was born about 1088 AD, and the genetic MRCA for BY18179 and FT16709 is BY18115, which has a TMRCA of 1041 A.D. This estimate is within 50 years of the reported birth date of 1088 for Tairdelbach Mór. (Update May 2024: the current TMRCA estimate for BY18115 is now 1047 CE, 95% CI 768-1270. Also, there are now 6 men called O’Connor sitting on the BY18115 branch.)
Another major branch of the Uí Briúin Aí were the Mac Dermot clan of Moylurg. This royal line also has a documented pedigree that stretches back for more than 30 generations from the present day to the medieval genealogies. A third cousin once removed of the present chief of the clan was approached and agreed to undertake Big Y testing. His results showed that he sits on a branch characterized by the SNP marker FTA43921. Subsequently, the current MacDermot clan chief undertook SNP testing and tested positive for the upstream SNP marker BY20594. (14) Plans are in place to proceed to Big Y testing and it is anticipated that the clan chief will also test positive for FTA43921.
The Mac Dermot clan of Moylurg is reportedly related to a McCormack clan with whom they share the common ancestor Conchobar, who died in 1251 A.D. Two McCormick men sit on the FT42402 branch of the Y-DNA haplotree, adjacent to the Mac Dermots of Moylurg. Their MRCA SNP is FT441685 and has a TMRCA of 1133 A.D. This is within 70 years of the estimated birth year for the common ancestor Conchobar, namely 1200 A.D., and thus the genealogical and genetic records are consistent. (Update May 2024: the current TMRCA estimate for FT441685 is now 1083 CE, 95% CI 742-1346.)
Another related clan carries the name McDonough and the common ancestor they share with the Mac Dermot and McCormack clans is Tomaltach na Cairrge (died 1207 A.D.). There is currently no known unique SNP that corresponds with this particular ancestor.
Yet another (more distantly) related clan goes by the surname Morris. The common ancestor they share with the Mac Dermot, McCormack, and McDonough clans is Tadg Mór, born about 1025 A.D. A single test-taker named Morris sits on an adjacent branch of the Y-DNA haplotree to the subjects discussed above, characterized by the SNP marker BY20593. The estimated birth year for Tadg Mór (1025 A.D.) falls within 85 years of the central estimate (1110 A.D.) for the TMRCA for BY20593, and falls well within the 95% Confidence Interval. (Update May 2024: the current TMRCA estimate for BY20593 is now 1064 CE, 95% CI 757-1305.)
The presence of these associated surnames on adjacent branches of the Y-DNA haplotree, the consistent branching structure, and the consistent TMRCA estimates between the CAST and DAST suggest that the medieval genealogies for this portion of the Uí Briúin Aí are consistent with the genetic record back to the level of Tadg Mór (born about 1025 A.D.), who is therefore associated with the SNP marker BY20593. This latter SNP connects with the A260 branch, which is associated with the Uí Briúin Bréifne & Uí Briúin Seóla branches, and is an immediate descendant of A259.
However, five generations further back in the medieval genealogies is an ancestor called Tadg mac Cathail (born about 900, died in 956) and he is supposed to be the common ancestor of both the Mac Dermots of Moylurg and the O Conor Don. However, this is where we encounter a major problem ...
How do we explain this inconsistency? There are several possibilities.
It is important to note that despite this disconnect between the two royal lines, they both have been carrying their respective genetic signature for a very long time (i.e., any DNA switch that may have occurred is not a recent event). The TMRCAs for their respective terminal SNPs indicate that the Mac Dermots have carried their specific DNA signature for about 700 years and the O Conor Don have carried their specific genetic signature for about 800 years. Furthermore, it seems unlikely that a random NPE along either line would result in a true genetic relationship this close in time (i.e., one within the timeframe of the dynasty as a whole and not, for example, several thousand years back). Therefore, while an NPE can never be completely ruled out, a genealogical arrangement after the fact (either due to incorrect oral transmission or purposeful political alteration) would seem more probable from the genetic evidence.
Another unexpected finding revealed by the DNA results, is the presence of a large cluster of men called O’Halloran (and variants), and a second large cluster of men called Mannion (indicated in red in Figure 4). They share a common genetic ancestor with each other and with the Mac Dermot’s of Moylurg who carried the SNP marker FGC5939.2 and lived about 569 A.D.
However, the O’Halloran surname is reported to descend from Oengus (another son of Brión, who lived in the 300s) and is associated with the Chiefs of Clann Fergaile, whereas the Mannion surname is associated with the kings of Sogain, who have no reported genealogical connection to the Uí Briúin Aí.
Why these surname clusters appear in this portion of the Y-DNA haplotree remains a subject for further research, but the TMRCA estimates tell us that the O’Halloran surname has been associated with their genetic signature (BY20816) for about 500 years, and the Mannion surname has been associated with their genetic signature (FT63002) for about 800 years, so if some sort of DNA switch has occurred, it is not a recent event in either case.
Evidence of deliberate falsification?
Lastly, there is a prominent clan in the Uí Briúin genealogies that is missing from this portion of the Y-DNA haplotree, namely the O’Malley clan of Mayo. The genealogy for this clan claims descent from Conall Oirisin, one of the other sons of Brión. (Conall Oirisin does not appear in the original list of Brión’s sons, and is likely a later politically motivated addition.) If this was indeed the case, then the O’Malleys of Mayo would also be expected to test positive for the SNP marker A259, but this is not the case.
In fact, the O’Malleys of Mayo fall under DF105, which is two steps further up the Y-DNA haplotree and dates to a midline estimate in the early third century.
This strongly suggests that the medieval portion of the genealogy of the O’Malley clan of Mayo has been inaccurately attached to the Uí Briúin genealogy, and supports other evidence that suggests that the early parts of the O’Malley genealogy may have been a deliberate falsification.
Discussion and conclusions
The comparison of the genealogical and genetic record has highlighted some important inconsistencies between the two:
However, overall there was generally good agreement between the medieval genealogies and the A259 portion of the Y-DNA haplotree (with regards to the clustering of surnames, the branching structure, and TMRCAs), especially in those branches that postdate the arrival of literacy in Ireland (around 600 A.D.). This suggests that the medieval genealogies of the Uí Briúin are broadly accurate (with the exceptions noted above) and that a genetic signal from our ancient forebears still survives in spite of 1,000 years of surname extinction, DNA switches (NPEs), surname switches, and anglicisation. This signal may become more clear as more people undertake comprehensive SNP testing (such as the Big Y test), thus blowing off the dust that has settled on the ancient genealogies, and revealing the pattern underneath.
Such SNP testing is necessary as some branches have small numbers, and some important branches may be under-represented due to a sparsity of surviving descendants on the direct male line. Thus, in time, the provisional conclusions from this study will hopefully be bolstered by additional SNP data.
Additional participants (especially those with extensive lineages) will help refine the TMRCA estimates and reveal more of the fine-detailed structure within the Y-DNA haplotree, allowing for more robust conclusions to be drawn regarding specific branches.
Having the expertise of an academic expert in medieval Irish history was an essential part of this study. Most Group Project Administrators are not specialists in this area, and their ability to access medieval sources is frequently limited to those that are available online. Having an academic expert helped to put everything in its proper context, facilitated the correct interpretation of data, and helped identify which sources were reliable and which sources should be treated with caution.
The Y-DNA haplotree is continuously evolving and already the analysis above is out of date - the TMRCAs have been further refined, and additional participants have been added to some branches. Branching may be rearranged further as the tree expands with more data.
This study would not have been possible without FamilyTreeDNA or its army of volunteer Group Project Administrators. FamilyTreeDNA has created not only the DNA tests, but also the infrastructure that makes running DNA projects possible. And Group Project Administrators play a vital role in recruiting participants, interpreting the genetic record, building interest and momentum in Y-DNA research, and advancing the science of genetic genealogy.
This analysis highlights the usefulness of Y-DNA as a tool for identifying inconsistencies between the medieval genealogies and the genetic record. Such findings shed new light on the medieval genealogies and will hopefully inspire future research involving cross-fertilisation and collaboration between the two disciplines of genetic genealogy and medieval Irish history.
Ideally, in time, we will see the digitisation and indexing of the entire corpus of medieval Irish genealogies, the correlation of the genealogies with the extant historical record, and the correlation of specific clans and surnames with specific branches of the Y-Haplotree.
References
Over the millennia, in a continuous process, Irish clans gave rise to subsequent clans. These descendant clans adopted specific surnames from about 900 A.D. onwards. Thus, any post-surname clans that descended from a specific pre-surname clan should be relatively closely related to each other genetically, and should therefore sit on adjacent branches of the Y-DNA Tree of Humankind (i.e., Y-haplotree), probably with the same overarching DNA marker.
But there are many important factors that influence if a particular surname has survived over the past 1,000 years or so, and if there are living descendants visible in the Y-DNA database today. Some of the most important of these factors include the following:
- Extinction of surnames: some Irish surnames have gone extinct. Some will have died out, others will have “daughtered out” (i.e., no male heirs to pass the surname forward to future generations). The rate of extinction could be as high as 95%. (3)
- Survival of the fittest: some of these post-surname clans became quite powerful within the Irish social system of the time, whilst others did not. It is likely that the more powerful clans had more surviving descendants than the less powerful clans, and therefore there is probably a greater chance of the surnames of the more powerful clans persisting over time, escaping extinction, and being in the Y-DNA database today.
- Lack of testing: some surnames may indeed exist today, but none of the surviving descendants bearing that surname have done a Y-DNA test. And therefore the surname doesn’t appear in the Y-DNA database. Alternatively, some people with the surname may have tested, but not enough to provide useful DNA data for analysis. Even a well-run surname DNA project might test less than 0.2% of surviving bearers of the surname. (4)
- DNA Switches (NPEs, or non-paternal events): some surnames may indeed exist today, but the surviving descendants bearing that surname have become “uncoupled” from the Y-DNA signature that was originally associated with it (i.e., an NPE or DNA switch has occurred). This could be due to a variety of different reasons (e.g., illegitimacy, infidelity, adoption). And so, even though the surname does still exist today, and may even appear in the database, it is no longer associated with the Y-DNA of the progenitor of the surname. This may occur in 33-55% of present-day descendants. (5)
- Surname Switches: This is another factor leading to a reduction in the number of descendants bearing a particular surname. Again, there are many reasons for this, but in medieval times, an important factor may have been a family changing their surname to that of their chief or lord as a sign of allegiance, fealty, or loyalty. This process has been termed “surname gravity”, where a less powerful family changes its surname to one associated with a more powerful family. In effect, less powerful surnames “gravitated” towards more powerful ones. (6) Such a change might also confer a degree of protection on the family in question. Such surname switches would mean that the surname in question becomes associated with “foreign” DNA i.e. Y-DNA that comes from a source other than the progenitor of the surname.
- Anglicization of surnames: throughout the 16th to 19th centuries, Irish surnames were translated from the Irish version to an English equivalent. In many cases, the original Irish version was “lost in translation” and attempts to accurately correlate the current English version of a surname with the previous Irish version can be very difficult, or at times impossible. (7) This is a particularly large-scale example of a surname switch – it affected an entire nation.
- Results are not made public: by default, Y-DNA results in the FamilyTreeDNA database are not publicly displayed on the webpages of Group Projects. Test takers have to manually reset this to allow public display but many people do not know this or how to do it. Secondly, if a test taker has not joined any Group Projects, their results will not be publicly visible. Thus, the data may be available, but inaccessible for research purposes.
The Uí Briúin dynasty of northwest Ireland
Around 2014, Paul Duffy from Dublin (genetic genealogist and Group Project Administrator) noted that quite a few surnames associated with the Uí Briúin dynasty of northwest Ireland fell under the SNP marker A259 (a descendant of M222). (8) Since then, various FamilyTreeDNA Group Projects (run by volunteer Group Project Administrators) have explored this possible connection.
The specific surnames that are reported to be descended from the various branches of the Uí Briúin dynasty are summarized in the table below, divided into those associated with more powerful (major) clans (whose members became High Kings) and less powerful (minor) descendant clans. Each surname has a list of named ancestors (recorded in various versions of the medieval genealogies) that goes back to the reported progenitor of the Uí Briúin dynasty, namely Brión, supposed son of Eochaidh Muigh-Meadhóin (spelt in a variety of ways and pronounced roughly Yuck-ee Mwee Maydoyn).
Table 1: Some surnames associated with the various divisions of the Uí Briúin dynasty
Branches of the Uí Briúin dynasty | Major clans | Minor clans |
Uí Briúin Breifne | O’Rourke, O’Reilly | McTiernan, McGovern, Ford, O’Donoghue, Finnegan, Connaghty, Duffy, Murphy, Gorey, Fanning, Brady, O’Reilly, McNight, Key, Cox, Guthrie, O’Carroll, Hannify, Flynn, Faughnan, Boylan, Moriarty, Murtagh, O’Rourke, McDonnell, McGilbride, Culreavy, Gray, MacNeill, Gore, Parrott, Pratt |
Uí Briúin Seóla | O’Flaherty | McHugh, McDonough, O’Donnell, Lewy, Kilkelly, McDermott Duff, McTiernan |
Uí Briúin Aí | McDermott of Moylurg, O’Conor Don | McManus, Flanagan, McDonough, McCormack, Morris, Flynn, Boland, Gilbert, Mullehan, Concannon, Fahy, O’Dermott Finn, Moriarty, Murtagh, Davie, Tumulty, O’Donnell, O’Kenny, Kearney, Finn, Mullen, MacMorrissey, Tighe, O’Crolly, Crowley, Mulrooney, MacLaughlan, McDermott Roe, McDermott Gall, Kenyon, Doyle, Malone, Cuniffe, Nugent, O’Connor Roe, McRory, McGeraghty, Hoban, Murray, O’Beirne, Barnewall, Quinn, Lennon, Strahan, Fallon, Kennedy, MacAneave, Gunning, Fallon, Hayes, Hughes, Finnaghty, Breen, Meaney, O’Hart, Sheridan, Mulkieran, Goonane, Murray, Mullen, Donnellan, Lawless, Early, Mulrennan, Gilchrist, MacGrane, Drennan, Conway, Fihily, Brogan, Moran, Fleming, Canavan, Benedict, Bennett, Rolan, Rowley |
Other surnames |
| O’Malley, O'Halloran |
Note that each branch of the Uí Briúin dynasty gave rise to multiple surnames. Sometimes the same surname arose independently in several branches (e.g., McTiernan, Flynn, McDonough).
So, in relation to the surnames above, there are two key questions:
- Are there enough male descendants in the Y-DNA database to sufficiently reveal a genetic pattern (should one exist)?
- Is the genetic pattern consistent with the medieval genealogies?
Methods
In order to address these two key questions, we collated data from over 350 test takers who had undergone SNP testing (usually the Big Y test), who tested positive for A259, and whose data was publicly available from online Y-DNA haplotrees and the public results pages of various FamilyTreeDNA Group Projects, run by volunteer Group Project Administrators.
From this data, we constructed a Y-DNA haplotree (for those branches below A259) that included the surnames of the tested individuals. We called this the DAST (DNA-Associated Surnames Tree). The DAST is available to download as Appendix 2 (37 kB) from the figshare website here.
We also extracted data from three versions of the medieval genealogies (MacFirbis, O Hart, Jaski) to construct a CAST (Clan-Associated Surnames Tree) that summarized the various surnames that arose from the Uí Briúin dynasty, as well as their lines of ascent to their common ancestors. (9,10,11) The CAST is available to download as Appendix 1 (57 kB) from the figshare website here.
We then compared the CAST (the genealogical record) with the DAST (the genetic record), looking for consistencies and inconsistencies between the two datasets.
The three key questions we asked when comparing the genealogical and genetic records were as follows:
- Do reportedly related surnames cluster together on a particular branch of the Y-DNA haplotree?
- Does the branching structure in the Y-haplotree mirror the branching structure in the genealogical record?
- Are the age estimates for the relevant branching points in the Y-haplotree consistent with the estimated birth of the common ancestor at the relevant branching points in the medieval genealogies?
The Uí Briúin dynasty in the medieval genealogies
The progenitor of the Uí Briúin dynasty is reported to have been Brión (spelt in a variety of different ways, and roughly pronounced Bree-own), who was said to be a half-brother of Niall of the Nine Hostages (NOTNH), and a supposed son of Eochaidh Muigh-Meadhóin (pronounced roughly Yuck-ee Mwee Maydoyn, as mentioned above). These people lived prior to the introduction of literacy in Ireland (about 600 A.D.) and thus we cannot be certain that they existed, or that their relationship to each other has been a) reported correctly and b) transmitted correctly down through the centuries since that time.
Eochaidh is reported to have had six sons in the earlier genealogies (probably the more accurate ones) and 24 sons in later genealogies (probably the more inaccurate ones). This is a good example of how the royal lineages “acquired” additional descendant lines as time went by, many being deliberately falsified and added to the genealogy for sociopolitical reasons.
Three of the sons of Brión’s great-great-grandson Fergus reportedly gave rise to prominent descendant lines which in turn gave rise to many kings and chiefs, some of whom gave rise to specific Irish surnames. These three branches were called the Uí Briúin Aí, Uí Briúin Seóla, and Uí Briúin Breifne, pronounced roughly Ay (as in hay), Show-la, and Breff-nuh. Figure 1 summarizes these three major branches and some of the surnames that arose from them (according to the medieval genealogies).
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| Figure 1: Descendants of Brión showing the three major branches of the Uí Briúin dynasty (the Uí Briúin Aí, Seóla and Breifne) and some of the surnames that they each produced (in yellow highlight). Note: a quo is Latin, meaning “from whom is derived.” |
We will focus on these three major branches one by one. Bear in mind that this study was conducted in 2023 and took almost one year to be published, and because genetic genealogy is a fast-moving science, additional data has since become available that further supports many of the conclusions that are detailed below.
Uí Briúin Breifne
This clan ruled over a large territory stretching across what are now counties Leitrim and Cavan. The genealogical record reports that there are two early branches within this clan: one gave rise to the surnames McTiernan and McGovern, and the other gave rise to the surnames O’Rourke, O’Reilly, and Ford (with known variant McAna).
When comparing the genealogical record (CAST) with the genetic record (DAST), these names do indeed cluster close to each other on the Y-DNA haplotree. In the DAST, there is a cluster of four men called McTiernan on the branch characterized by the SNP marker FGC55184, and another cluster of McGovern men on FGC34296 (1 subject) and FGC59200 (7 subjects). These branches are offshoots of an over-arching branch characterized by the SNP marker A5902, which in turn is a descendant of A260, which is a descendant of A259. Furthermore, the branching structure in the genetic tree (DAST) is consistent with the branching structure in the genealogical tree (CAST), as illustrated in Figure 2 .
The MRCA (most recent common ancestor) for the McTiernan and McGovern branches (in the genealogies) is Máenach, who lived sometime between 600 and 760 A.D. (approximately). The genetic MRCA is A5902, and the TMRCA (time to most recent common ancestor) for this SNP has a central estimate of 709 A.D. (95% confidence interval 432-940 A.D.). This TMRCA estimate is consistent with the estimated birth year of Máenach … although with such a large confidence interval (i.e., just over 500 years) it would be difficult not to be! (Update May 2024: the current TMRCA estimate is now 664 CE, 95% CI 382-900. The range remains just over 500 years but the central estimate has decreased by 45 years.)
Incidentally, birth years are estimated from dates of death (and occasionally dates of birth) that are found in the ancient Irish annals (such as the Annals of the Four Masters). (12) These are a very useful accompaniment to the medieval genealogies and attest to the existence of many of the individuals named therein.
On this point, Y-DNA alone cannot confirm that a specific named individual actually existed. There must be supportive documentary evidence, and it is the totality of the evidence (documentary and genetic) that will determine the likelihood that a specific individual actually existed. Many of the more distant ancestors in the fabricated genealogies will be fake.
Another important point to make is that even though an MRCA passed on a particular DNA marker to all his descendants, this does not mean that that specific DNA marker arose in that specific MRCA. It may have arisen in his father, his grandfather, or further back along his direct male line. A specific research methodology exists for determining if a particular SNP marker arose in a specific named individual, and this entails testing validated descendants of two documented brothers. A good example of this involves the Stewart Kings of Scotland, where DNA testing identified a DNA marker (S781) that arose in in Sir John Stewart of Bonkyl (born in the mid-1200s). This DNA marker identifies his descendants (i.e. the Stewarts of Bonkyl) and distinguishes them from those of his brother James, 5th High Steward of Scotland, whose descendants include King Robert II, King Robert III, and King James I of Scotland. (13)
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| Figure 2: Genealogy of the Uí Briúin Breifne and a proposed mirror-image of the relevant portion of the Y-haplotree. Key: 95% CI = 95% Confidence Interval; no. = number of subjects with that particular surname. Note: Ancestral names do not necessarily correspond to a specific SNP. MRCAs (where available) are indicated in the genealogies by a light purple highlight. TMRCAs in black text refer to those in the recent publication (abstracted from FamilyTreeDNA’s Time Tree in April 2023) and TMRCAs in blue text were abstracted in April 2024. The ancient remains of Ballyhanna 331 tested positive for A259, indicating that the SNP marker was present in northwest Ireland since at least the 1200s. Click to enlarge the image. |
An adjacent branch to A5902 above is characterised by the SNP marker BY3338. On this branch, there is a cluster of 20 men called O’Reilly, three men called Ford, and two men called O’Rourke. Each cluster is associated with a distinct branch characterized by a specific SNP marker (BY11723, O’Reilly; BY18113, Ford; and BY38364, O’Rourke). All three branches are offshoots of the overarching SNP marker BY3338, which, in turn, is a descendant of A260, which is a descendant of A259.
In the genealogies, these three surnames share a common genealogical ancestor called Cernach, who is estimated to have been born about 710 A.D. The three sub-branches have a genetic MRCA in the SNP marker BY3338, and the TMRCA for this ancestral SNP is 769 A.D.(95% confidence interval 518-978). Thus the estimated birth year for Cernach (710 A.D.) falls within the (460-year) confidence interval for BY3338, indicating that the genealogical and genetic TMRCAs are not inconsistent. (Update May 2024: the current TMRCA estimate is 702 CE, 95% CI 443-920.)
In the genealogies, these three surnames share a common genealogical ancestor called Cernach, who is estimated to have been born about 710 A.D. The three sub-branches have a genetic MRCA in the SNP marker BY3338, and the TMRCA for this ancestral SNP is 769 A.D.(95% confidence interval 518-978). Thus the estimated birth year for Cernach (710 A.D.) falls within the (460-year) confidence interval for BY3338, indicating that the genealogical and genetic TMRCAs are not inconsistent. (Update May 2024: the current TMRCA estimate is 702 CE, 95% CI 443-920.)
So, for the Uí Briúin Breifne, the clustering of reportedly related surnames, the branching pattern, and the TMRCA estimates for common ancestors demonstrate consistency between the genealogical record and the genetic record.
Uí Briúin Seóla
Uí Briúin Seóla
A similar story exists for the Uí Briúin Seóla. The major surnames in this part of the genealogies include McHugh, McDonough, and O’Flaherty (with variants Clardy and Clarida).
Figure 3 shows that these surnames cluster together in this portion of the Y-haplotree on branches characterized by the corresponding SNP markers FGC42414 (McHugh), FGC65259 (McDonough), and both FT367336 and YFS1251634 (O’Flaherty). The overarching SNP marker BY11725 is their most recent common genetic ancestor, which is a descendant of A260, which is a descendant of A259.
The common genealogical ancestor for the McDonoughs and O’Flahertys is reported to be Muiredach Mór ua Flaithbertaig (born about 970 A.D.), and the corresponding genetic MRCA is BY18145, which has a TMRCA estimate of 1137 A.D. Even though there is a 170 year difference between the two estimates, the genealogical estimate (970 A.D.) is still within the 95% confidence interval of the TMRCA estimate, and therefore cannot be deemed to be inconsistent. (Update May 2024: the current TMRCA estimate for BY18145 is now 1136 CE, 95% CI 864-1350.)
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| Figure 3: Genealogy of the Uí Briúin Seóla and a proposed mirror-image of the relevant portion of the Y-haplotree. Key: 95% CI, 95% Confidence Interval; no., number of subjects with that particular surname. Note: Ancestral names do not necessarily correspond to a specific SNP. MRCAs (where available) are indicated in the genealogies by a light purple highlight. TMRCAs in black text refer to those in the recent publication (abstracted from FamilyTreeDNA ’s Time Tree in April 2023) and TMRCAs in blue text were abstracted in April 2024. Click to enlarge the image. |
This is a good example of how crude the genetic TMRCA estimates really are. From a genealogical perspective, it would be really helpful to be able to narrow down the range to about 10 years on either side of the central estimate, but this is unlikely to ever happen— the stochastic nature of the mutations will simply not allow it.
Instead, we are likely to be stuck with wide ranges (e.g., +/- 200 to 500 years) for the foreseeable future. In time, we might be able to narrow the range to +/- 50 years (for some well-tested branches) but that will only happen when a lot more people have undertaken the Big Y-700 test. Until then, TMRCA estimates will remain crude and will lack the precision desired by genealogists, which makes them especially prone to misinterpretation and confirmation bias.
The most recent common ancestor that the McHughs share with the McDonoughs and O’Flahertys in Cenn Fáelad mac Colgain. The corresponding genetic MRCA is BY11725 with a limited TMRCA estimate of some time in the 700s. This is reasonably close to the estimated birth year for Cenn Fáelad mac Colgain, which is about 620 A.D. (he was assassinated in 682). So again, there is no obvious inconsistency between the genealogical and the genetic record. (Update May 2024: the current TMRCA estimate for the newly-added SNP marker BY11725 is now 563 CE, 95% CI 231-837.)
Thus the clustering of reportedly related surnames, the branching structure below BY11725, and the TMRCA estimates in this part of the Y-DNA haplotree mirror what we see in the medieval genealogies for the Uí Briúin Seóla. However, the number of people involved in the analysis of the Uí Briúin Seóla (10) is much smaller than that for the analysis of the Uí Briúin Breifne (37) and additional SNP data is needed to help bolster these provisional conclusions.
Uí Briúin Aí
It is when we come to the Uí Briúin Aí that we start to see some important inconsistencies between the genealogical and genetic records.
This clan held sway over territories in what is now northern county Roscommon, extending into county Sligo. The major surnames in this part of the genealogies are Flanagan, O’Connor, McManus, McDermott (and the associated surnames McCormack & McDonough, and Morris).
Figure 4 shows eight men called McManus forming a cluster characterized by the SNP marker BY18179. A nearby cluster of three men called O’Connor sit on the adjacent branch, characterized by the SNP FT16709. Among this group is an immediate relative of the current chief of the O Conor Don clan. This royal line has a continuous lineage for over 30 generations (named ancestor by named ancestor) from the present day back to the medieval genealogies.
The MRCA for the McManus and O Conor Don clans is Tairdelbach Mór (roughly pronounced Ter-lock More), who was born about 1088 AD, and the genetic MRCA for BY18179 and FT16709 is BY18115, which has a TMRCA of 1041 A.D. This estimate is within 50 years of the reported birth date of 1088 for Tairdelbach Mór. (Update May 2024: the current TMRCA estimate for BY18115 is now 1047 CE, 95% CI 768-1270. Also, there are now 6 men called O’Connor sitting on the BY18115 branch.)
Fourteen generations back from Tairdelbach Mór is the common ancestor that the McManus clan and the O Conor Don line share with the Flanagan clan, namely Muiredach Muillethan. Two Flanagan men sit on a branch of the Y-DNA haplotree characterized by FT12117, and the common genetic ancestor that these men share with the McManus and O Conor Don men carried the SNP marker Y166841. The TMRCA for this SNP is 424 A.D., whereas the estimated birth year for Muiredach Muillethan is 650 A.D. This latter date is 226 years older than the TMRCA for Y166841, but this still falls within the 95% c onfidence interval for the TMRCA (i.e., 32-745 A.D.), and is thus not inconsistent with the genetic record. (Update May 2024: the current TMRCA estimate for Y166841 is now 340 CE, 95% CI 64 BCE – 670 CE. And the estimated birth year for Muiredach Muillethan of 650 A.D. now just barely falls within this revised 95% Confidence Interval.)
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| Figure 4: Genealogy of the Uí Briúin Aí and a proposed mirror-image of the relevant portion of the Y-DNA haplotree. Key: 95% CI, 95% confidence interval; no., number of subjects with that particular surname. Note: Ancestral names do not necessarily correspond to a specific SNP. MRCAs (where available) are indicated in the genealogies by a light purple highlight. TMRCAs in black text refer to those in the recent publication (abstracted from FamilyTreeDNA’s Time Tree in April 2023). Click to enlarge |
Another major branch of the Uí Briúin Aí were the Mac Dermot clan of Moylurg. This royal line also has a documented pedigree that stretches back for more than 30 generations from the present day to the medieval genealogies. A third cousin once removed of the present chief of the clan was approached and agreed to undertake Big Y testing. His results showed that he sits on a branch characterized by the SNP marker FTA43921. Subsequently, the current MacDermot clan chief undertook SNP testing and tested positive for the upstream SNP marker BY20594. (14) Plans are in place to proceed to Big Y testing and it is anticipated that the clan chief will also test positive for FTA43921.
The Mac Dermot clan of Moylurg is reportedly related to a McCormack clan with whom they share the common ancestor Conchobar, who died in 1251 A.D. Two McCormick men sit on the FT42402 branch of the Y-DNA haplotree, adjacent to the Mac Dermots of Moylurg. Their MRCA SNP is FT441685 and has a TMRCA of 1133 A.D. This is within 70 years of the estimated birth year for the common ancestor Conchobar, namely 1200 A.D., and thus the genealogical and genetic records are consistent. (Update May 2024: the current TMRCA estimate for FT441685 is now 1083 CE, 95% CI 742-1346.)
Another related clan carries the name McDonough and the common ancestor they share with the Mac Dermot and McCormack clans is Tomaltach na Cairrge (died 1207 A.D.). There is currently no known unique SNP that corresponds with this particular ancestor.
Yet another (more distantly) related clan goes by the surname Morris. The common ancestor they share with the Mac Dermot, McCormack, and McDonough clans is Tadg Mór, born about 1025 A.D. A single test-taker named Morris sits on an adjacent branch of the Y-DNA haplotree to the subjects discussed above, characterized by the SNP marker BY20593. The estimated birth year for Tadg Mór (1025 A.D.) falls within 85 years of the central estimate (1110 A.D.) for the TMRCA for BY20593, and falls well within the 95% Confidence Interval. (Update May 2024: the current TMRCA estimate for BY20593 is now 1064 CE, 95% CI 757-1305.)
The presence of these associated surnames on adjacent branches of the Y-DNA haplotree, the consistent branching structure, and the consistent TMRCA estimates between the CAST and DAST suggest that the medieval genealogies for this portion of the Uí Briúin Aí are consistent with the genetic record back to the level of Tadg Mór (born about 1025 A.D.), who is therefore associated with the SNP marker BY20593. This latter SNP connects with the A260 branch, which is associated with the Uí Briúin Bréifne & Uí Briúin Seóla branches, and is an immediate descendant of A259.
However, five generations further back in the medieval genealogies is an ancestor called Tadg mac Cathail (born about 900, died in 956) and he is supposed to be the common ancestor of both the Mac Dermots of Moylurg and the O Conor Don. However, this is where we encounter a major problem ...
We have seen at the start of this section how the line of Tadg mac Cathail is associated with the SNP marker Y166841, which in turn is also an immediate descendant of A259. And this indicates a major inconsistency between the genealogical and genetic records— the line of the Mac Dermots of Moylurg does not connect with the line of the O Conor Don at the level of their presumed ancestor (Tadg mac Cathail, died 956). Instead the genetic record indicates that they connect about 400-500 years earlier, via an ancestor who carried the SNP marker A259 and who would have lived within a few generations of Eochaidh Muigh-Meadhóin, father of Brión (the progenitor of the Uí Briúin). This inconsistency between the genealogical and genetic record is highlighted by a red line in Figure 4.
How do we explain this inconsistency? There are several possibilities.
- The medieval genealogies are incorrect, and one or more of the ancestral lines have been erroneously attached to the wrong ancestor. This is not inconceivable given that Brión (the overarching ancestor for the Uí Briúin) probably lived some time in the fourth century, when oral transmission of the genealogies was the only way in which they were communicated from generation to generation. Thus an error may have been introduced into the earlier portions of the genealogies and this has been passed down through the generations and up to the present day. This is perhaps the most plausible explanation. Furthermore, we must always bear in mind that some genealogies may have been deliberately falsified for political gain.
- The medieval genealogies are correct, but a DNA switch (i.e., NPE ) took place somewhere along the line of the O Conor Don. This could have happened (for example) somewhere between Tairdelbach Mór (born 1088, died 1156) and his ancestor Tadg mac Cathail (died 956), but this would mean that we are incorrect in our proposition that the two Flanagan subjects under FT12117 represent descendants of Flannacán (great-great-great- grandson of Muiredach Muillethan r.696-702). Of note, the TMRCA for the two Flanagan men is only 1761 A.D., so currently we can only infer that the Flanagan surname has been associated with this particular SNP for about 250 years. More data is needed to determine if the association goes back to medieval times. And we need to bear in mind that the chances of a DNA switch (NPE) occurring on this ancestral line at some time between 1000 A.D. and 1761 A.D. are in the region of 25-40%. (5)
- The medieval genealogies are correct, but a DNA switch (i.e., NPE) took place somewhere along the line of the Mac Dermot of Moylurg. This could have happened (for example) some time prior to Tadg Mór (born about 1025), assuming that our deductions are correct regarding the associations between the surnames Mac Dermot, McCormack, McDonough and Morris. However, if this is the case, then it would imply an error at the very top of the Uí Briúin genealogy. In other words, the Uí Briúin Aí would descend from Y166841 (‘son’ of A259) whilst the Uí Briúin Breifne and Uí Briúin Seóla would descend from A260 (another ‘son’ of A259). And this means that the progenitors of each clan could not have been brothers. If they were, this would mean that the SNP A260 arose independently in two brothers (or close cousins), and that is a virtual impossibility. So if this scenario is correct, then the early parts of the Uí Briúin genealogies are incorrect.
- Some other explanation? Or a combination of the above?
It is important to note that despite this disconnect between the two royal lines, they both have been carrying their respective genetic signature for a very long time (i.e., any DNA switch that may have occurred is not a recent event). The TMRCAs for their respective terminal SNPs indicate that the Mac Dermots have carried their specific DNA signature for about 700 years and the O Conor Don have carried their specific genetic signature for about 800 years. Furthermore, it seems unlikely that a random NPE along either line would result in a true genetic relationship this close in time (i.e., one within the timeframe of the dynasty as a whole and not, for example, several thousand years back). Therefore, while an NPE can never be completely ruled out, a genealogical arrangement after the fact (either due to incorrect oral transmission or purposeful political alteration) would seem more probable from the genetic evidence.
Another unexpected finding revealed by the DNA results, is the presence of a large cluster of men called O’Halloran (and variants), and a second large cluster of men called Mannion (indicated in red in Figure 4). They share a common genetic ancestor with each other and with the Mac Dermot’s of Moylurg who carried the SNP marker FGC5939.2 and lived about 569 A.D.
However, the O’Halloran surname is reported to descend from Oengus (another son of Brión, who lived in the 300s) and is associated with the Chiefs of Clann Fergaile, whereas the Mannion surname is associated with the kings of Sogain, who have no reported genealogical connection to the Uí Briúin Aí.
Why these surname clusters appear in this portion of the Y-DNA haplotree remains a subject for further research, but the TMRCA estimates tell us that the O’Halloran surname has been associated with their genetic signature (BY20816) for about 500 years, and the Mannion surname has been associated with their genetic signature (FT63002) for about 800 years, so if some sort of DNA switch has occurred, it is not a recent event in either case.
Evidence of deliberate falsification?
Lastly, there is a prominent clan in the Uí Briúin genealogies that is missing from this portion of the Y-DNA haplotree, namely the O’Malley clan of Mayo. The genealogy for this clan claims descent from Conall Oirisin, one of the other sons of Brión. (Conall Oirisin does not appear in the original list of Brión’s sons, and is likely a later politically motivated addition.) If this was indeed the case, then the O’Malleys of Mayo would also be expected to test positive for the SNP marker A259, but this is not the case.
In fact, the O’Malleys of Mayo fall under DF105, which is two steps further up the Y-DNA haplotree and dates to a midline estimate in the early third century.
This strongly suggests that the medieval portion of the genealogy of the O’Malley clan of Mayo has been inaccurately attached to the Uí Briúin genealogy, and supports other evidence that suggests that the early parts of the O’Malley genealogy may have been a deliberate falsification.
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| Figure 5: Genealogy of the O’Malley clan of Mayo. Their placement on the Y-DNA haplotree lies immediately below DF105 (red line), indicating that if A259 represents the Uí Briúin, then the medieval genealogy of the O’Malley’s is inaccurate. Click to enlarge the image |
Discussion and conclusions
The comparison of the genealogical and genetic record has highlighted some important inconsistencies between the two:
- The O’Connor and McDermott lines do not connect where they should genetically. A DNA switch (NPE) may have occurred on one or the other line, but it is not currently possible to say in which line it occurred, or why. Alternatively, and possibly more likely, a long-standing mistake in the genealogical record may be present.
- The lineage of the O’Malley clan of Mayo appears to be inaccurately attached to the Uí Briúin genealogy, suggesting a long-standing mistake in the early portion of the O’Malley genealogy, or a deliberate falsification for sociopolitical gain.
- The reasons for the close genetic connection between the prominent O’Halloran and Mannion clusters, and their genetic association with the Mac Dermot of Moylurg, remain to be determined. Of potential relevance, it is reported that Brión (progenitor of the Uí Briúin) was buried on land that belonged to the O’Halloran clan.
However, overall there was generally good agreement between the medieval genealogies and the A259 portion of the Y-DNA haplotree (with regards to the clustering of surnames, the branching structure, and TMRCAs), especially in those branches that postdate the arrival of literacy in Ireland (around 600 A.D.). This suggests that the medieval genealogies of the Uí Briúin are broadly accurate (with the exceptions noted above) and that a genetic signal from our ancient forebears still survives in spite of 1,000 years of surname extinction, DNA switches (NPEs), surname switches, and anglicisation. This signal may become more clear as more people undertake comprehensive SNP testing (such as the Big Y test), thus blowing off the dust that has settled on the ancient genealogies, and revealing the pattern underneath.
Such SNP testing is necessary as some branches have small numbers, and some important branches may be under-represented due to a sparsity of surviving descendants on the direct male line. Thus, in time, the provisional conclusions from this study will hopefully be bolstered by additional SNP data.
Additional participants (especially those with extensive lineages) will help refine the TMRCA estimates and reveal more of the fine-detailed structure within the Y-DNA haplotree, allowing for more robust conclusions to be drawn regarding specific branches.
Having the expertise of an academic expert in medieval Irish history was an essential part of this study. Most Group Project Administrators are not specialists in this area, and their ability to access medieval sources is frequently limited to those that are available online. Having an academic expert helped to put everything in its proper context, facilitated the correct interpretation of data, and helped identify which sources were reliable and which sources should be treated with caution.
The Y-DNA haplotree is continuously evolving and already the analysis above is out of date - the TMRCAs have been further refined, and additional participants have been added to some branches. Branching may be rearranged further as the tree expands with more data.
This study would not have been possible without FamilyTreeDNA or its army of volunteer Group Project Administrators. FamilyTreeDNA has created not only the DNA tests, but also the infrastructure that makes running DNA projects possible. And Group Project Administrators play a vital role in recruiting participants, interpreting the genetic record, building interest and momentum in Y-DNA research, and advancing the science of genetic genealogy.
This analysis highlights the usefulness of Y-DNA as a tool for identifying inconsistencies between the medieval genealogies and the genetic record. Such findings shed new light on the medieval genealogies and will hopefully inspire future research involving cross-fertilisation and collaboration between the two disciplines of genetic genealogy and medieval Irish history.
Ideally, in time, we will see the digitisation and indexing of the entire corpus of medieval Irish genealogies, the correlation of the genealogies with the extant historical record, and the correlation of specific clans and surnames with specific branches of the Y-Haplotree.
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| Figure 6: The main divisions of the Uí Briúin dynasty and the SNP markers currently associated with them. This may change as new data becomes available. |
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| Figure 7: A combination of Figures 2-5 above into a single figure. Click to enlarge |
Maurice Gleeson
Kyle DePew
May 2024
References
- Donnchadh Ó Corráin, Creating the past: the early Irish genealogical tradition. Peritia 12 (1998) 177–208.
- Kyle DePew, Maurice Gleeson & Bart Jaski, Tracing the Sons of Brión. The R1b-A259 Y-DNA Subclade and the Uí Briúin Dynasty of Connacht. Peritia 34 (2023) 9-45. DOI10.1484/J.PERIT.5.136859. Also available at https://www.brepols.net/products/IS-9782503604060-1
- Rob Spencer, personal communication (2024), based on his Extinction Simulator (available at http://scaledinnovation.com/gg/extinctionDemo.html)
- James Irvine, Y-DNA of a Scots-Irish Diaspora. Genetic Genealogy Ireland (2018), Belfast. Video presentation available at https://youtu.be/vvRBkYM1wQE?si=puvFrbY9MduG7Gmt&t=725
- Maurice Gleeson. Goodbye NPE, Hello SDS - some causes of Surname or DNA Switches (2018) Article available at https://dnaandfamilytreeresearch.blogspot.com/2018/07/goodbye-npe-hello-sds-some-causes-of.html
- Maurice Gleeson. Same Surname, Different DNA - some potential medieval explanations (2024) Available at https://dnaandfamilytreeresearch.blogspot.com/2024/05/same-surname-different-dna-some.html
- Rev. Patrick Woulfe, Irish Names and Surnames (1923). Available at https://www.libraryireland.com/names/anglicisation-irish-surnames.php
- See 7th comment (by Paul Ó Duḃṫaiġ) in response to Debbie Kennett’s article (2015) at https://cruwys.blogspot.com/2015/12/my-thoughts-on-dna-cymru-part-3-and.html
- Nollaig Ó Muraíle (ed), Leabhar Mór na nGenealach: The great book of Irish genealogies. Compiled (1645–66) by Dubhaltach Mac Fhirbhisigh, 5 vols (Dublin 2003–2004). A massive compilation, edited with translation and indices, but currently not digitized or available online.
- John O’Hart, Irish pedigrees, or: the origin and stem of the Irish nation (1892) 5th edn (Dublin 1892), available at https://www.libraryireland.com/Pedigrees1/title.php. O’Hart’s data are included because they are a frequently consulted online resource and his numbering system allows for ease of navigation and identification of specific individuals.
- Bart Jaski, The traditional rule of succession in early Ireland. Appendix 2: Genealogical tables of medieval Irish royal dynasties (unpubl. Ph.D. thesis, Trinity College Dublin, 1994), available online via https://uu.academia.edu/BartJaski. These tables are a comprehensive amalgamation of all the major ancient genealogical sources apart from Mac Fhirbhisigh
- Annala Rioghachta Eireann: Annals of the Kingdom of Ireland by the Four Masters from the earliest period to the year 1616 translated by John O'Donovan (2nd ed.), 1856, 7 volumes, Royal Irish Academy. Links to the 7 volumes are available at https://en.wikipedia.org/wiki/Annals_of_the_Four_Masters#Editions_and_translations
- G. S. Holton, Discovering unknown medieval descents: a genetic approach – medieval genealogy for the masses. Foundations 12 (2020) 2–15; available online at: https://fmg.ac/publications/journal/vol-12/650-jn-12-09.
- Mac Diarmata Big News (Oct 2023). Available on the forum of the Genelach Dáil Cuinn Project at https://genelach.org/forum/viewtopic.php?t=845
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