R1b-CTS4466 Plus

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Display of Y-DNA Results

The DNA Results pages, both Classic and Colorized Charts, group the participants according to their positive results for the SNPs associated with the Irish Type II haplotype, in the order of the Family Tree Haplotree.  The CTS4466  haplotree is displayed on the Background page, and participants can also see it on the Haplotree & SNPs link of their Dashboard with an indication of where their terminal SNP lies in the hierarchy.  Anyone not yet SNP tested shows a default R-M269 in red font in the Haplogroup column.  More SNPs are being identified regularly through the BIG Y test, and the groupings will change accordingly.

The CTS4466 Haplotree

The haplotree for CTS4466 continues to expand as more Big Y test results arrive.  It is getting very bushy, but for simplicity’s sake, here is a compressed tree with just the main branches:

A7751 is a small subclade at the top of the tree with typical Welsh surnames. 

S1115 (incl Z3023)  begins to branch off as CTS4466 men begin to migrate.

A212 is geographically associated with Northern Ireland, Scotland and England, suggesting a migration north, then across the Irish Sea.

BY23591 is the second small subclade containing obvious Welsh surnames.

FGC84010 is a major branching, with the vast majority of surnames found in it to be of Munster origin.

A541 beneath it splits into three significant subclades:

S1121 includes the majority of Eóganacht surnames across Munster, intermingled with earlier tribal groups, notably the Corca Laidhe and Corca Dhuibhne.

A1135 is a bit more broadly based, with Scottish and English surnames as well.

A151 seems to be a seafaring group, with surnames native to Kerry in the west to Waterford in the east of Munster, as well as a branch found up in Scotland and even Norway.

A663 is a sibling branch to A541, notable for surnames found in the Seven Septs of Laois.

FT263830, also a sibling branch of A541 and A663, and may have continental origins.

Explanation of the Groupings in the Y-DNA Charts

The structure of the groups is based on the CTS4466 haplotree displayed on the Background page that Joe Carroll updates regularly.  We use a five-digit numeric system at the beginning of each group to maintain the order in the spreadsheet as new branches are identified and inserted.  Focusing on the last SNP listed identifies the branch.  A  '/' indicates equivalents and a '>' indicates an SNP downstream of the previously listed SNP.  Kits that have been tested elsewhere to a deeper level than their FTDNA test, and those that have individual SNP tests or SNP Pack tests but not BigY tests show as "*****.a Tested to *****".

The '...a - Presumed...' groups are identified as kits with a close family link to the SNP group directly above them, usually having exact matching haplotypes and common ancestors or close Family Finder matches.  The "*****?" groups are probably positives for the relevant SNPs directly above them in the list, based on being a close genetic distance to those who have tested positive for the SNPs and sharing surnames and/or particular marker values.  Nigel's phylogenetic tree is also used for reference.  These are only interpretations, and as others test around them the interpretation is apt to change.  There are still some adjustments being made, and if you are unclear about the group in which you are placed, feel free to contact the administrator assigned to your branch.  Our names are listed in the chart above.

Updates on the Extensive Y-DNA SNP Testing in the Project


By now, we have hundreds of  BIG Y results, and more keep coming in. There is a huge amount of data to review.  There is a downloadable VCF file available to each participant with the raw data from their test; and for an additional fee, Family Tree is also providing a very extensive BAM file that contains even more data than available in the VCF folder.  

Debbie Kennett’s blog provides some interesting insights into the test: 

Roberta Estes has also prepared an informative blog post: 

For those of you who have taken the BIG Y test, Family Tree has a 'Big Y Results & Matches' page on their Help Center at https://help.familytreedna.com/hc/en-us/sections/360001357875-Big-Y-Results-Matches.
Maurice Gleeson has a very worthwhile blog, DNA and Family Tree Research, that can be found at https://dnaandfamilytreeresearch.blogspot.com/2019/08/getting-most-from-your-new-big-y-700.html.

Alex Williamson, one of the gurus of the genetic genealogy community, has a very comprehensive
The Big Tree at https://www.ytree.net/ that analyses all the BIG Y results to which he has access.  He is not currently updating it, but our participants who tested earlier and submitted their data can be seen individually on the link P312>L21>DF13>FGC11134 at.  If you click onto a specific SNP, you will often be directed to a second page with additional information.  Family Tree have adopted Alex's format (with his permission) for their Block Tree link.


The questions in the minds of everyone who is interested in the Irish Type II haplotype are where did it originate and how is it related to the ancient Eóganacht tribes who ruled Munster unopposed for over 500 years, from about 500 to 1000 AD.

At the beginning of 2012, the Munster Irish Project - https://www.familytreedna.com/public/MunsterIrish - was initiated to study the genetic heritage of the province.  This was prior to the discovery of the CTS4466 SNP that has come to be associated with the Irish Type II haplotype.  Its Y-DNA Results table is grouped by the tribes to which the surnames belong (according to the ancient genealogical tracts) regardless of their haplotype.  It was apparent from the beginning that the Irish Type II haplotype is found throughout Munster; and while almost all of the names associated with the Eóganacht do have a significant amount of Irish Type II in their lineages, it is not limited to those surnames.  At the moment, the few members of the Alltraige, Corca Baiscinn, Eóganacht Rosarguid, Ossraige and Ui-Feaba are the only tribes whose associated surnames don't currently include any Irish Type II.

The degree of presence of Irish Type II in historically older tribes, most notably the Corca Laidhe and the Corca Dhuibhne, cannot be reasonably attributed merely to NPEs, adoptions, war (and the accompanying rape/pillage), etc.  It suggests that the progenitor from whom all “Irish Type II” peoples flourished significantly predated the emergence of the Eóganacht as a ruling force in Munster.  What also needs to be considered is the fact that a number of subclades/clusters of CTS4466 contain individuals whose family origins are found in different geographical areas - in the north of Ireland, Scotland, parts of England and the Scandinavian countries, and even a few other continentals.  Travel by sea and the ease of trade that the coastal routes afforded between all these areas, not to mention the active slave trade (Dublin was a noted Viking slave market that existed from the 9th into the 12th centuries) no doubt played a part in the distribution of the Irish Type II as well as all other Irish haplotypes.

The mythical ancestor of the Eóganacht, Eógan Mór, is supposed to have descended from the Milesians, whose arrival in Ireland forms the closing chapter to the ancient Book of Invasions (Leabhar Gabalah Éireann) an 11th century compilation of earlier texts which identifies this event as the final invasion where the Milesians land in Kenmare Bay and bring the Gaelic culture to Ireland.  The sons of Mil, or Miles Espania (the Spanish soldier) were supposed to have invaded Ireland from Spain.  Some of the early scholars suggested dates as early as 1700 BC based on the Book of Invasions.  This genesis myth was taken quite seriously during the period of the Celtic Revival, but there are few who give it much credence now.

While the degree of DNA testing done in men of recent Iberian origin is currently not as extensive as could be wished, there is no evidence of the Irish Type II haplotype in this region, so that it would currently be difficult to support an Iberian origin for the Eóganacht.  If there was a Milesian invasion with male progeny surviving to this day, it's quite doubtful they were Irish Type II.

In any case, to consider the relevance of the Irish Type II haplotype to the genealogy of the Eóganacht, Nigel McCarthy has extensively researched the annals and ancient genealogies of the tribes of Munster and has produced a significant paper discussing this history and has developed possible pedigree trees of the various Eóganacht septs based on ancient genealogies, overlaid with the CTS4466 tree with an indication where appropriate of participants with Eóganacht surnames who have tested to their current terminal SNP.  This Phylogenetic alignments with genealogies of descent from Ailill Ólom can be downloaded from The McCarthy Surname (Y-DNA) Study ahttps://mccarthydna.wordpress.com/.  It should be noted that there are genetic anomalies in the the most prominent lineages of the Eóganacht Cashel and Eóganacht Raithlind that diverge from the purported common ancestry of the Eóganacht dynasties and their proposed relationship to the Irish Type II haplotype.

The McCarthy Surname Study shows Y-DNA evidence that suggests that the Callaghan and McCarthy Mٕór/Eóganacht Cashel lineages are not Irish Type II but DF21 >> L362. (See “Summary of Findings” at https://www.familytreedna.com/groups/mccarthy-surname-study/about/results.)

The most populous branch of the O'Sullivan/Eóganacht Cashel is CTS4466 >> L270, which is a distinct branch of S1121, quite separate from the rest of the S1121 tree under Z16252 where the other Eóganacht surnames are found.

Extensive review of pertinent literature by The O'Donoghue Society has led to the conclusion that the ancestry of O'Donoghue of the Glens lies in the Co. Tipperary/
Eóganacht Cashel O'Donoghues (who are sometimes ignored in genealogical tracts) and not the Eóganacht Raithlind, as suggested in most ancient annals.  

Similar research indicates that the O’Donoghue Mór lineage is not Irish Type II either, but DF21 >> BY11464.  (See https://www.odonoghue.co.uk/projects/project-1/interpretations). 

There are a number of charts/attachments at the end of Nigel's paper proposing possible Y-DNA relationships amongst the various Eóganacht surnames. The order of the SNP hierarchy does not always coincide with the structure of the Eóganacht genealogy, requiring a number of lines and arrows pointing to the reality of the SNP tree with the purported interrelatedness of the various septs of the Eóganacht.

All the Eóganacht surnames are found downstream of A541.  On the left, there is the obvious branch of L270, dominated by the O'Sullivans and including McGillicuddy, consistent with ancient genealogies, but the other main Eóganacht Cashel surnames of McCarthy and O'Donoghue do not share that SNP except for 2% of Irish Type II McCarthys, which is not considered significant enough a proportion to validate such a genealogy.  Instead we show four different surviving lineages attributable to the Eóganacht Cashel.

While we are able to present O’Keefe’s position in a manner consistent with the ancient genealogies, more testing of O’Keeffes is required to confirm this. Note also that many other (mostly Munster) surnames are associated with the O’Keeffe SNP A159.

Almost all other Eóganacht surnames are found under Z16251 and A1135.  Alongside these are pockets of surnames that have no hint of Munster or even Irish origin, often with more diversified haplotypes and/or on earlier branches of the tree.  In some instances, these can be explained by permanent migration out of Munster and/or across the Irish Sea.  However, there is not always an apparent rationalization for non-Eóganacht surnames carrying the same SNPs as Eóganacht surnames.

Rev O’Keeffe’s Book of Munster, a 1703 summary of earlier sources of greater or lesser renown, does list a large number of Munster surnames as derived from the tribal progeny of the Eóganacht Raithlind; it remains to be seen whether such claims can be validated. A number of these, such as O’Callaghan, O’Connelly, O’Donoghue and O’Leary have other independent origins in Munster and often in the rest of Ireland.

Some historians consider the Eóganacht Loch Lein to be the original Eóganacht, from which all other septs evolved, migrating eastwards into greater Munster.  There is so far no evidence to support an early independent Eóganacht Loch Lein lineage. The two Moriartys and one Carroll representing this sept and who have deep clade tested all show a relatively late first millennium ancestry shared with O’Donoghue of the Glens, which is unexpected and puzzling.  However, others of these surnames may be found in different areas of the tree, so more testing is required to draw reliable conclusions on the origins of this foundation sept.

The Uí Liathan and Uí Fidgeinti are also tribes with lineages attributed to Eóganacht origins.  As with Eóganacht Raithlind, further surnames purporting to be associated with these, such as Gleason and O’Corráin, not represented in our project at the time of the tree construction, are omitted for clarity for the time being.  Most Donovans and Collinses, the modern day flag bearers of Uí Fidgeinti origins who are Irish Type II, are found beneath Z16259 alongside others with compatible Thomond origins such as O’Hourihane, O’Brien and O’Regan. (O’Briens in Thomond and McCarthys in Desmond were the most powerful families in mediaeval Munster so it is not unexpected that many will have taken these names through “clan affiliation” rather than a paternal genetic descent.)  However, the surnames Donovan and Collins may also be argued as having Corca Laidhe origins, and the identification of some Z16259 O’Driscolls hint at this as an alternative origin. The situation is further confused by the historical record of a migration of Uí Fidgeinti southwards from their Co. Limerick homelands into territories occupied by Corca Laidhe in 1178 and beyond.  (It could, however, be argued that the O’Driscoll name might then have also been assumed by some through affiliation to the dominant “clan” of the area, since I-P37 is the most prominent haplogroup of the O'Driscolls.)

Clearly, from the range of surnames and phylogenetic tree structure under A1135, either Fiachu Fidgenid, the founder, had a far greater progeny than has previously been recognised or the Uí Fidgeinti were just one branch of a major sublineage.  The tree currently suggests the latter. There are many names in the tree structure between A1135 and Z16259 suggestive of locations beyond Munster, although a few, such as Griffin, O’Hearn, Irwin and Allen, further support a Thomond association.  Since Aine is very close to Emly, a 10th / 11th century focal point of the later McCarthy dynasty, we are also investigating possible Eóganacht Aine connections with surnames other than Kerwick/Kirby, represented to date by just one participant who shares ancestry with one of the two significant Daly groups.

The A151 branches are listed at top right.  Subject to further testing now underway, at present it comprises 1) two distinct single surname branches: O'Connell (of Dingle Bay) and MacAulay (of the Outer Hebrides), 2) branches with a strong Scandinavian presence and 3) a subclade of predominantly English, Welsh and Scottish names but including the only other Irish name, one of two Irish Type II Brazils. (The other is in the Z16254 subclade under A1135, but neither corresponds with a possible O'Breassail sept as indicated in the historical Eóganacht genealogies).  There have been several interesting discussions on the Forum about these families. You need to join the Forum (https://groups.yahoo.com/neo/groups/R1b-CTS4466-Plus/info) to view them, and we hope more of you will join to see these discussions as well as the other data available there.

The A212 and A663 branches are parallel with A541, but do not feature A541’s Eóganacht (Munster) surnames.  While A212’s geographical location is Ulster (300CE), A663 is geographically associated with Leinster (Laois) since 300CE and includes Seven Septs of Laois (Leix) surnames; Moore, Lawlor, Dowling and variations of the surname McAvoy/McEvoy, as well as, (Upper Ossory) surnames Dulany/Delaney.  This does not preclude a Munster origin as they may have developed in the progeny of migrants who had travelled northwards/eastwards across the Irish Sea.  It's always possible that they could be indicative of the location of the common ancestry of all on the subject tree, though a migration south does not fit well with the early historical information available to us. 

There is the promising potential of Wales as a source from whence the early Irish Type II ancestors migrated to Munster.  The 00020-00050 and 20020-21000 groups in the Results spreadsheet contain kits dominated by Welsh surnames.  They are all in branches at the 'top of the tree', being the early mutations after CTS4466 and its equivalents.  Even branches of FGC11134, the SNP upstream of CTS4466 on the L21 haplotree, contain Welsh surnames, giving further credence to the possibility of a Welsh origin.  The A212 and A663 branches may have originated from a Welsh source traveling north and then across to Ireland from there.  There have been lively discussions of origins on our Forum.

It is apparent that the validated Y-DNA hierarchy of the Irish Type II tree does not coincide with the Eóganacht genealogies in a straightforward manner.  The DNA is real.  The ancient tracts, not only about the Eóganacht but all the other tribes present in ancient Ireland, are notorious for being conflated, inflated, if not fabricated.  However, that does not mean that they are entirely invented, and the old adage, 'where there is smoke there is fire' could apply here.  Our attempts at correlating the Y-DNA and the ancient annals/genealogies do not reconcile the apparent differences and conflicts, and it's possible they never will, but there is a degree of structure to what we have presented in the chart.

The phylogenetic tree from A541 downward supports a concept of one, perhaps early first millennium common ancestor whose progeny is represented in many Eóganacht tribes.  Within Irish Type II, surnames purporting derivation from these tribes are predominantly found in the S1121 subclade of A541, suggesting that if there is a figurehead to this family, S1121 would have been his terminal SNP.  However, in view of the considerable other surnames present in those A541 branches, even taking  into account migrations into and out of Munster, NPEs and surnames gained by clan affiliation, it is problematic to suggest that the common ancestor can be claimed by the descendants of those Eóganacht tribes alone.  Some inter-relationships within the historical genealogies may be viable, but others would need adjustment to be compatible with the genetic data.

The progenitor of the Irish Type II could have been a recent ancestor of the semi-mythical Eoghan Mór, with the S1121 and A1135 subclades of A541 appearing in his progeny, but then again that progenitor might be someone even more ancient. With the relative prevalence of Irish Type II in the Corca Laidhe tribes and their territorial predominance throughout much of Munster prior to their overthrow by the Eóganacht, who disposed them of most of their territory, it's not impossible that the Irish Type II originated within these earlier tribes.  We need to be open minded about the possibilities.  Wales seems to be in the mix in a significant way.

The chart is not meant to be all inclusive at this point and it will be an ongoing project.  We anticipate expanding it to include additional data regularly.  Along with that, our challenge is to try and determine the relative validity of the various ancient Irish tracts and other historical documents that chart the history of all those who are CTS4466/Irish Type II, both in Ireland and wherever their wanderings took them, and discover how they are all related.  No easy task, but we look forward to updating this study as more NGS and Big-Y data becomes available and we broaden our knowledge.


There is an understandable interest in how old CTS4466 is.  We must first recognize that the TMRCA is only the time to the most recent common ancestor - not necessarily the original one.  The man with the initial SNP that defines the subclade represented by CTS4466 and its equivalents almost surely lived much earlier, perhaps by even 1500 years or more, due to a bottleneck evidenced by a significant number of equivalent SNPs to CTS4466 itself, implying a long period in which the lineage was contained within a limited family organisation, before S1115 and A7751 occurred.  There were probably more branches in the lineage at one time, but any offshoots from the numerous equivalent SNPs or indeed other branches of CTS4466 itself, based on our current data, have died out.  Hence, the common ancestor to whom we try to estimate a TMRCA period is an embodiment of a complex lineage going back that we will almost certainly never be able to completely decipher.  What we can hope for is continued discoveries of further branches as we receive more BIG Y results for not only the CTS4466+ participants in our project, but also the directly upstream SNPs of FGC11134+ but CTS4466- participants.  These upstream SNPs may also provide clues of their own to the origins of CTS4466.


There are various methods of calculating TMRCA - based on the number of SNPs separating different subclades, the number of mutations present in the dataset chosen, STR diversity, etc.; and different dates have been calculated, depending on mutation rates used, counting of mutations and/or number of SNPs between branches, percent of probability considered, and factors for bottlenecks, back mutations, etc. taken into account, which are variables that can never be known for sure.  While the results are sometimes similar between different citizen scientists and more commercial statisticians studying DNA, even professional statisticians have to admit that there can be no certainty in the level of accuracy any of these methods provide, and it's possible there could be significant underestimations.

It had been suggested that the ancestor of the Irish Type II may have lived sometime in the first half of the first millennium A.D, but increased data has pushed that possibility back a bit.  You can find current estimated TMRCAs for most of the branches of CTS4466 at Alex Williamson’s Big Tree at https://www.ytree.net/DisplayTree.php?blockID=21.  Click on the particular SNP you are interested in and you’ll get a second page, which many include an Age Analysis at the bottom of the page.  For CTS4466, Alex (using Iain McDonald's calculation method) suggests 'the median age of this block is 2316.5 YBP (367 BC). The 95%confidence interval is 854 BC to 17 AD'.

Ancient Irish DNA

In addition to the citizen scientists who are studying the modern DNA of all those who have tested, the professional scientists and academics have for some years now been gathering data from ancient bones.  There is a growing database of the DNA of ancient specimens all around the world; and there is a paper just published - Neolithic and Bronze Age migration to Ireland and establishment of the insular Atlantic genome - by a collaboration between Smurfit Institute of Genetics, Trinity College, and School of Geography, Archaeology and Palaeoecology, Queen’s University Belfast, headed by Professor Dan Bradley, in which the DNA of four prehistoric individuals has been tested for the first time.  It includes a Neolithic woman from a megalithic burial at Ballynahatty, Co. Down, estimated to be 3343–3020 BC based on associated artefacts and three Bronze Age males from Rathlin Island off the coast of Co. Antrim estimated to be of an age of 2026–1534 BC.  The paper can be downloaded for free at http://m.pnas.org/content/suppl/2015/12/23/1518445113.DCSupplemental/pnas.1518445113.sapp.pdf.

The female was determined to be of predominantly Near Eastern origin, indicating there was an influx of early farmers to the island during the Neolithic era.  Her haplogroup was HV0.  The males had a substantial heritage of Bronze Age herders going back to the Pontic Steppes.  They were tested to L21, DF21>Z30233 and DF21>S5488.  

This is not the forum to go into more detail of the paper and its results, but anyone interested can access the paper and its accompanying appendix SI Appendix, Section S1 - listed on page 1 of the document.

Maybe someday Y-DNA testing of other skeletal remains which can be reliably dated by other means will give us an indication of the earliest occurrence of CTS4466 in Munster or elsewhere, if the trail leads us to a different origin.  At the moment, Wales is a possible candidate.

Other Relevant Papers

The Beaker phenomenon and the genomic transformation of northwest Europe - https://www.nature.com/articles/nature25738  (Published February 2018 - full paper by subscription)

Insular Celtic population structure and genomic footprints of migration - http://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1007152  (Published January 2018)

The Irish DNA Atlas: Revealing Fine-Scale Population Structure and History within Ireland - https://www.researchgate.net/publication/321781959_The_Irish_DNA_Atlas_Revealing_Fine-Scale_Population_Structure_and_History_within_Ireland  (Published December 2017)

Neolithic and Bronze Age migration to Ireland and establishment of the insular Atlantic genome - http://www.pnas.org/content/113/2/368  (Published January 2016)

Last updated 29th Jan 2024