McCarthy Surname Study
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Last updated: 12 December 2021


For a study of McCarthy genetic genealogy in relation to other Munster surnames please go to

For further information and analysis of the Irish Type II haplotype of R-L21 Group A McCarthys please go to

All R-L21 Group B McCarthys who have tested 37 STR markers or more are also enrolled in the R Z16526 and Subclades Project (formerly known as the R-P314 Haplogroup Project), for which please go to This elucidates the pre-surname era origins of McCarthys deemed to share in the paternal ancestry of the McCarthy kings of Cashel and Desmond; these origins are not at all what Irish histories tell us!



The results of Y-DNA testing at FTDNA for haplotype and haplogroup determination are shown on the DNA Results page on this website. About 10% of McCarthys have been tested or predicted as being within haplogroups E1b1b1, G, I1, I2a1 and R1a1. However, as indicated on the Background page of this website, FTDNA predicts that about 90% of McCarthys have common ancestry in the progenitor in whom SNP R-M269 occurred.

The latest breakdown of McCarthy Study members by haplogroup is given in Fig. 3 on our Scrapbook website ( while an indication of how these various groupings relate to one another on the (male) human phylogenetic tree will be found in Fig. 1 on the same site. To avoid bias arising from focused studies of particular families, participants joining the study as a consequence of other recent family members' participation are not counted in the statistics displayed in Fig. 3. Also shown in this figure is data for the 66 anonymous McCarthy participants in Prof. D G Bradley and B McEvoy’s Trinity College, Dublin study of 2003/04.

As indicated in the said Fig. 1, 81 to 87% of McCarthys are to be found in the various subclades of SNP R-DF13 (the principal genetic 'son', or perhaps 'grandson', of SNP R-L21). For convenience these subclades are labelled with 'McCarthy R-L21 Group' letters A, B, C, D, E etc., allocated as indicated below. These letters have been arbitrarily assigned (A and B are as used by the founder Administrators of this Study) and bear no relation to the use of letters defining primary haplogroups on the tree of mankind.

Prior to 2013, little was known about the branching of the phylogenetic tree beyond R-DF13 as defined by SNPs. We worked therefore largely with haplotype data deriving from tests of STR markers such as those comprising FTDNA's Y-DNA37, 67 and 111 tests to postulate the tree structure from early in the Bronze Age onwards. The start point for the vast majority of McCarthys was thus the haplotype associated with SNPs P312, L21 and DF13, known as the Atlantic Modal Haplotype (AMH), or, when based on FTDNA's Y-DNA67 test, Super Western AMH (SWAMH). This is believed also to be the actual ('ancestral') haplotype of those in whom these SNPs occurred, i.e no detectable STR mutations occurred going from P312 to DF13 in FTDNA's first 67 markers. Only when extending to include FTDNA's Panel 5 (its 68th. to 111th. STR markers) is a difference seen between the modal, and very likely ancestral, haplotypes associated with P312 and L21. Haplotypes (Y-DNA37, 67 or 111 data) still play an important role in our data analysis, even where our members have greatly enhanced the identification of their Y-DNA profile with a Big Y-700 'SNP discovery' test.

Fig 4 on our Scrapbook site shows the probable ancestral haplotype pertaining to the ancestor shared by all McCarthys for each of our R-L21 Groups, along with the corresponding SNP path up to a time somewhere near the birth of this ancestor. STR Mutations which have occurred since the time of SNP R-L21 are colour-highlighted. In a similar manner, the ancestral haplotype pertaining to the most recent ancestor shared by all McCarthys in each of the haplogroups of SNPs BY3540 (under R-U152) and R-DF89 (under R-U106) is also provided. It is the presence of most of these highlighted alleles (and not necessarily low genetic difference as indicated in members' Y-DNA matches data) which is used to determine to which of our various McCarthy groups new members belong when they cannot claim irrefutable membership through SNP testing. It should be recognised that in each group, other mutations not evident in this table will have occurred subsequent to the time of the group's common McCarthy ancestor, and so some mismatches are to be expected. These include 'back mutations', with reversion, for example, to the status at the time of SNP R-L21.

The 2004 analysis of McCarthy Surname Study results by our founder Administrators, provided at the foot of this webpage for reference, had only the benefit of the 12 STR markers (FTDNA's 'Panel 1'), but was able to divide the McCarthys into three groups, the third being a miscellany. The identification of the first two, A and B (now R-L21 Groups A and B) proved to be, albeit unwittingly at the time, major milestones in the development of Munster genetic genealogy.

The project provides phylogenetic trees at for most of the McCarthy groups, tracing the paternal genetic ancestry of its members from around the end of the neolithic age to the present day.



Two major clusters account for about 50% of all McCarthys. It is argued in Phylogenetic alignments with genealogies of descent from Ailill Ólom on our Scrapbook website that the shared ancestor of all McCarthys in the first of these clusters was Ailill Flann Bec, that he was born about 285 A.D., and that SNP A541 occurred in his birth or that of an immediate ancestor. This is our McCarthy R-L21 Group A. The second cluster, accounting for 30% of McCarthy males today, is our R-L21 Group B, headed by SNP ZS4606, on a completely different SNP path from R-L21 and DF13. If this did not occur in Cárthach, king of the Eóghanacht of Cashel, himself, it most likely occurred in his father Saorbhreathach (anglicised as Justin). The tree based on ancient genealogies from Ceallachán of Cashel (died ca. 954) down to brothers Cormac Fionn and Domhnall Got Mac Cárthaigh (born towards the end of the 12th century), presented in Fig. 2 at, aligns precisely with the R-L21 Group B tree phylogenetic tree, the key mutations from which have been added to Fig.2.

The evidence supporting this conclusion is as follows:

  1. The only Callahans / O'Callaghans sharing paternal ancestry with McCarthys in the past 1200 years or so are the 11% which have the SNP R-L362 which has, since 2011, also been observed in all McCarthys in R-L21 Group B. 

  2. Whereas all R-L21 Group B McCarthys are tested or deduced positive for SNP ZS4606,  Big Y tests on several of the O'Callaghan / Callahan cluster have revealed them to be negative for this SNP but positive for mutually exclusive SNP A11018. All share SNP L362, and, where tested, its several equivalents* which currently define a bottleneck* period before ZS4606 and A11018.

  3. The various annals suggest the male progeny of Cárthach was numerous by the 17th century, when most disappear from Irish records as a consequence of the destruction of the gaelic order. While R-L21 Group B accommodates about 30% of all McCarthys with a common ancestor born in the era of Cárthach's birth, no other McCarthy cluster sharing a common ancestor as recent as this has more than about 5% of the surname.

  4. One participant whose paternal ancestry is claimed in Samuel Trant McCarthy's The MacCarthys of Munster, as descending from the Sliochd Cormac of Dunguile, a second descended from the M(a)cCarthys of Ardcanaght, and a third from a Ballyvourney family with lore of MacCarthy Mór origin have all tested positive for SNP A5813 and its equivalent FT28017, then subsequently SNP A9070. A fourth with documentation identifying his MacCarthy Muscraighe (of Muskerry) origins has also tested positive for A5813 and FT28017 but is negative for A9070 (See again Fig. 2). These are all progeny of Cormac Fionn. Others with these two SNPs, A5813 and FT28017, also generally have, where identifiable through their paper trails, most distant known ancestry in the areas in which the progeny of Cormac Fionn prevailed, viz. Co. Kerry, N.W. Cork and Muskerry.

  5. Mac Carthys Rabagh and Tallin, described or implied in the literature as subsepts in the progeny of Domhnall Got Mac Cárthaigh, have tested positive for ZS4598 and / or its 'equivalent', FGC76176; so have a purported McCarthy Reagh and numerous other members with West Cork origins, consistent with a provenance in Domhnall Got.

  6. While estimating TMRCAs (Time to the most recent ancestor) is an inexact science, there is no reason to argue that those relating to the occurrence of SNP ZS4606 and the later mutually exclusive SNPs A5813 and ZS4598 (one or the other of which has been found positive in almost all R-L21 Group B McCarthys who have tested for them) are inconsistent with the ancient genealogies if A5813 is assigned to Cormac Fionn or an immediate descendant thereof and ZS4598 to Domhnall Got.

* A bottleneck occurs when a number of SNPs are identified in an interval without their being any branching off the tree. The paternal line is seen to have hung by a thread. The SNPs within the bottleneck period are said to be 'equivalent'. Clearly bottlenecks are subject to being broken up by new discoveries.

Also with reference to Fig. 2, note that there is as yet no evidence of L362 among McAuliffes or MacCarthy Cremins, so their origin according to these genealogies is unproven; in fact those few McAuliffes who have tested have the Irish Type II haplotype shared with the R-L21 Group A McCarthys (though there is almost no evidence for a shared ancestor later than the first millenium) while MacCarthy Cremins are strongly associated with our R-L21 Group E.

Prior to Ceallachán of Cashel, the ancient genealogies claim a descent going back to Conall Corc, the first king of Cashel, who lived between the 4th and 5th centuries, then via Ailill Flann Bec to Eoghan Mór and finally his father Ailill Ólom (aka Oilioll Olum, died 234 according to the Annals of the Four Masters: see Background page). This line supposedly generated later surnames such as O’Sullivan, O’Dennehy, O’Mahoney, O’Keeffe, O’Donoghue, O’Moriarty (all of Eóghanacht tribes), and O’Donovan and Collins (with both Uí Fhidhgheinti and Corca Laidhe claims). All these names are indeed found - most in abundance - not only sharing a provenance in SNP R-A541 and the Irish Type II haplotype of McCarthy R-L21 Group A, but often with an inter-relationship demonstrating precise alignment between the ancient genealogies and the phylogenetic tree. As for the McCarthys themselves of our R-L21 Group A, they are sprinkled through many different branches each emanating from well before the 11th century,

The fundamental conclusion of our Study is therefore that the paternal ancestry of the MacCarthy kings of Cashel and Desmond, although certainly going back to Ceallachán of Cashel and may be a little beyond in alignment with ancient genealogies, does not originate in Ailill Ólom, Eoghan Mór, Ailill Flann Bec and Conall Corc

That 20% of McCarthys are found among the progeny of Ailill Flann Bec should not be surprising since the Irish type II haplotype associated with SNP A541 and its subclades is the dominant genetic lineage in south-west Ireland, the region in which the MacCarthy dynasty floursihed. Likewise Eóghanacht surnames such as O'Donoghue, O'Mahony, O'Moriarty and O'Sullivan, and perhaps others of the region such as O'Driscoll and O'Shea unsurprisingly appear in the subclades of R-ZS4606 indicating fathering by progeny of Cárthach. For example, the senior, MacCarthy Mór, line flourished in Co. Kerry from the 13th century onwards, in the presence of O'Sullivans and O'Moriartys, and we find these names in the subclade of SNP A5813; Domhnall Got Mac Cárthaigh usurped ownership of much of the O'Mahony homeland and in the subclade of SNP ZS4598 we find some O'Mahonys.

How long the paternal ancestry of Ceallachán of Cashel had been in Munster and whence it had arrived is as yet undetermined. This is being studied and reported in the R Z16526 and Subclades Project,, where it will be learned that clusters of more distantly related names sharing Iron Age ancestry, such as O'Leahy, Kennedy, O'Mara, Heaney and Ogan, Higgins, Chisholm, McAlister and Eubanks, contribute to the story.

DNA testing has shown that, as a rough rule of thumb, about 50% of present day carriers of gaelic surnames deriving from a monogenetic source (such as O'Keeffe and O'Sullivan are believed to be) no later than the eleventh century will trace back to a single ancestor who lived around the time the name came into being, i.e they show as a tight-knit cluster in Y-DNA results and can truly be considered as direct descendants of their legendary progenitor. The remainder will have gained the name through any of the means akin to those described under "Diversity among McCarthys" on the Background page of this website. However, for McCarthys the largest cluster with a common ancestor about a 1,000 years ago comprises only 30% of us (those of R-L21 Group B) at best, and if this group were not the haplotype of Cárthach, the figure would not exceed 5%. Although some separate O'Carty septs may have contributed a few McCarthys to these figures, this apparent anomaly is attributable to a much higher percentage of present day McCarthys having gained the name through clan affiliation as a consequence of the dominating power of the MacCarthy dynasty in south Munster in the first half of the second millenium. (The same effect is seen with the McCarthys' great Munster rivals, the O'Briens (and variants thereof), less than 30% of whom have the Irish Type III (aka Dalcassian) haplotype deduced as being that of the eponymous Brian Boru).

The following sections look at each of the McCarthy subgroups in more detail.

HAPLOGROUP E1b1b1 (E-M35.1)
The E1b1b1 tree at shows the haplogroups assigned by FTDNA to our E1b1b1 members. From various sources, it is deduced that SNP E-M35.1 and a block of over 150 'equivalent' SNPs occurred during a period extending from about 35,000 to 25,000 years ago. Our members are found in three distinct divisions, with SNP paths:

(i)   M35.1>....>Z1902>V12>...>S8397,
(ii)  M35.1>...>Z1919>...>V13>...>FGC14092 and
(iii) M35.1>...>Z1919>...>V22>,,,>CTS11721.

An Iron Age or later ancestral haplotype has been estimated on our E1b1b1 tree at the end of each of these paths. (i) and (iii) are clearly associated with Normans who came to Ireland from 1169 onwards. Fitzgeralds feature in both but the first has strong associations with the de Roche family of Co. Cork.

The strong Welsh connections of (ii) could also be attributable to a Norman provenance but a more likely origin candidate lies in Roman soldiers of Balkan origin who manned forts such as that at Abergele in North Wales then remained in place on retirement from the Roman Army. Upon completion of service (25 years), Roman troops were allowed to become citizens and retire. Less than 20% of known troops (from Roman records) actually returned home, but tended to retire in the location of their last station. There are records of Thracian units in England, including tombstones inscriptions and other indications of troops who did this, and a study of the Y-DNA of the present-day males in at least two garrison towns (one being Abergele) revealed approximately 35% E1b1b1 whereas elsewhere in Roman-occupied Britain it is as low as 1% (
A further closely-related subgroup of a McCarter and McCartys, all in the E1b1b1 subclade, and including our our former Co-Administrator Kevin D McCarty, has left the project.  Painstaking research by Kevin led him to the conclusion that the surname derivation of this group is a spelling variant of McArthur, a clan occupying the north-west shores of Loch Lomond, Scotland, and its hinterland.  Many McArthurs moved to Ulster during the plantation period; here their names were frequently recorded as McCarter, as pronounced by these Scots, and this was later adapted to McCarty by some on subsequent migration to the USA. To further complicate the situation in respect of this group, it is most closely aligned phylogenetically with a different clan which occupied nearby territories in Scotland, that of the Kilpatricks and Calhouns, who shared a similar pattern of migration first to Ulster and then on to the United States. This implies a surname change event before migration from Scotland. Since these E1b1b1 McCarters and McCartys have no true connection with the McCarthys of Munster, this group has now relocated to the Calhoun and Kilpatrick Projects. These MacArthurs are found in a 'cousin' subclade of that of SNP FGC14092, headed by SNP Y16733 and sharing origins very approximately at the beginning of the Bronze Age. Potential members of this McCarthy Study who belong in the E1b1b1 haplogroup should first review the likelihood that they have a similar surname mode of origin, and if so, join these alternative, more appropriate, projects instead.


For information on the origins of these haplogroups you are referred to the excellent accounts on the Eupedia website, at:

A tree is provided on our Scrapbook site for the four I1 members None is closely related to any of the other three and it seems likely that they acquired their McCarty name in USA.


For information on this haplogroup please refer to the I2a Project website at

The two similar haplotypes among the members of this McCarthy Group look as if they would belong to Isles Group A in the I2a project and likely test positive for SNP PF4135. This is the signature of many O'Driscolls for which I2a accounts for 55% of this surname. All but one of the O’Driscolls who have tested to 111 markers distinguish themselves from other Isles Group A participants with an allele count of 9 at the slow mutating Y-GGAAT-1B07 (rather than 11 seen elsewhere in this group). It will be interesting to see if other surnames of West Cork origin, and particularly McCarthys, in haplogroup I2a replicate this.

The O’Driscolls claim descent from the Corca Laidhe tribes of southwest Cork. One of these suspected McCarthy 'Isles Group A' participants has family lore of belonging to the Clan Teige Ilen McCarthy sept, who occupied lands immediately to the north of Skibbereen,  Historical works give no reliable origin for this sept. The McCarthy participant has no matches nearer to any O’Driscoll than 32 / 37 and this suggests his most probable point of common ancestry with the O'Driscolls could be as early as the time surnames were coming into use. 

Agnomen positively identified as pertinent to McCarthys in Haplogroup I2a:    Clan Teige Ilen

Haplogroup of R-U152. Tested / predicted R-M269>...>L151>P312>U152>BY3550>...>BY3537

R-U152 is known as an Alpine Celt marker. It is assumed to have arrived in Ireland - where it accounts for about 1.5% of the male population - from Britain, where various discussion suggests both pre-Roman and Roman era arrivals, the latter in the manner described for haplogroup E1b1b1 above.

Big Y testing of kits 115106 and B6821 reveals that they share over 20 SNPs under U152 including BY3537, the provisional 'lead' SNP for the subclade pending futher breakdown. Their haplotypes are shared by some Noonans / Newmans, from Irish O hIonmhaineáin (later
Ó Núanáin).  MacLysaght (in 'Irish Families') indicates that the Noonans were erenaghs of the church of St. Beretchert in the parish of Tullylease, in the barony of Duhallow, Co. Cork.  Other Noonans (as modern-day Newmans) are closely related to O'Callaghans / Callahans among the progeny of Ceallachán of Cashel, from whom the R-L21 Group B McCarthys also derive. These O'Callaghans were also domiciled in the barony of Duhallow until disturbed in Cromwellian times.

Two of the McCarthy kits in this group belong to a father and son from a townland just outside of Skibbereen in West Cork. This family were tenant farmers at least from the late 1700s. The remainder of the group comprises an American family with a documented presence in the Colonies at least as early as the early 1700s.

HAPLOGROUP of R-U198. Tested / predicted R-M269>...>L151>U106...>U198>...>S15627>DF89

Two of the three participants in this group have established Dunmanway area origins, one being a descendant of the genealogist and author Daniel MacCarthy Glas. However identification of R-U106 as their haplogroup is inconsistent with the genealogy spelt out in A Historical Pedigree of the Sliochd Feidhlimidh. The MacCarthys of Gleannacroim. All three participants in this group have now tested Big Y-700 and from analysis of the data no two appear to share paternal ancestry longer than the other. It is estimated that their last shared ancestor was about nine generations back; this fits very well with the notion that they represent lineages of the three sons of Feidhlim, grandson of Tadhg-an-Duna (I) Mac Carthy, viz.: Dermod-an-Duna, Owen (or Eugene) and Cormac (aka Charles of Lorraine).

Agnomen positively identified as pertinent to this group:    Glas

R-L21 GROUP A:  SNP Sequence R-L21>DF13>FGC11134>A146>CTS4466>S1115>A541 (Irish Type II haplotype)

The modal (and probably ancestral) haplotype associated with this group has already been noted as Irish Type II. It accounts for about 20% of McCarthys, but as already indicated, less than 5% share common ancestry as recent as 1,000 A.D. At least 50% of O’Sullivans, 50% of O'Keeffes and southern O’Donoghues, and over 30% of O’Mahonys, all names claimed to be of Eóghanacht origin, have Irish Type II haplotypes.

CTS4466 was identified as a "signature" SNP corresponding to the Irish Type II haplotype in 2012, and with the introduction of NGS testing such as FTDNA's Big Y, about 15 SNPs occurring in the same period as the series of STR mutations which characterise the Irish Type II haplotype have been identified.  This implies a bottleneck period of perhaps 1,500 years in which almost all branches off the lineage leading to the Irish Type II haplotype have failed to survive. Just a few early ones have been discovered, as indicated on the postulated phylogenetic tree provided at This multi-sheet tree shows all Irish Type II McCarthys who have tested to 37 STR markers or beyond, as well as most other particpants in the R1b-CTS4466 Plus Project who have tested to 111 markers or determined their terminal SNP beyond CTS4466 itself. It will be seen that McCarthys so far appear only in the subclades (branches) denoted by the following SNP sequences:

  • CTS4466>S1115>A541>S1121>L270 (the path of most Irish Type II O'Sullivans)

  • CTS4466>S1115>A541>S1121>Z16251 (beyond which McCarthys appear in a number of lower level subclades)

  • CTS4466>S1115>A541>Z21065>A195>A761>A88  (with the one McAuliffe who has tested to this extent being A195 +ve but thereafter negative).

  • CTS4466>S1115>A541>A151 (two isolated McCarthys).

McCarthys for whom there is only data from STR testing and who are not obvious close matches of others who have indulged in Big Y or other SNP testing are shown on the left hand side of sheet 1 pending appropriate SNP testing which will definitively place them in a subclade on sheet 3 and beyond.

From the tree it will be seen that the Irish Type II haplotype is apparent also in surnames derived from Munster tribal origins other than the Eóghanachta and in many surnames associated with other parts of the ‘Isles’. This might be explained in some cases by an efflux of Munster peoples through marriage alliances, trading and warring who did not return, and therefore carried their haplotypes into other parts of Western Europe in general and the Isles in particular, often places where surnames did not come into use until much later. Those in the A151 subclade appear to have travelled the furthest, with one group in Scandinavia and another the MacAulays of the Outer Hebrides: departure from Munster as Viking slaves is a distinct possibility here. 

The undersigned has presented an article available to R-L21 Group A members who have joined the R1b-CTS4466 Plus Project and its forum ( ) in which SNP A541 is estimated to have occurred early in the first millennium A.D. (Article title: Irish Type II explored through Uí Chairpri Aebda , file name Mutation rates for Z16259 timeline.pdf ). On this basis, though, it does seem feasible for the Irish Type II O’Sullivans, O’Donoghues, O'Keeffes, O’Mahonys and McCarthys to all have common ancestry in a powerful figure in an early Munster tribal grouping which evolved into the later Eóghanachta, Uí Fidgeinti and perhaps other groups, one such as the semi-mythical Oilioll Olum. Ancient genealogical tracts suggest that his grandson Ailill Flann Bec  was the last in the line shared by both Eóghanacht peoples and Uí Fhidgeinte, and certainly the traditional derivation of the O'Keeffes, O'Donoghues and O'Mahonys from the former and O'Donovans from the latter aligns very well with the genetic data and estimated time scales. The corresponding genetic routes are via Z16251 and A88 respectively.  

The most well-known McCarthy agnomen in R-L21 Group A is Cnoic, 'of the hill' (also known as Cnuc, Cnuic). This is found in a subclade of SNP A88 alongside many Crowleys and a couple of Cronins, with whom they are estimated to have shared common ancestry in the 11th century.

McCarthy Cruig is found alongside a McCarthy Glas under SNP L270; both have roots in the Keenrath / Togher area, within Gleann na Chroim; however their paternal ancestry is unrelated to the aforementioned Glas of haplogroup R-U106.

MacCarthy Gaibhdeach has been found alongside a number of surnames in a subclade defined as Z16251>Z18170> FGC29279>S1126>A726. However there may be no common 2nd millenium ancestry with these others, SNP A726 likely having occurred in the second half of the first millenium A.D. We await new participants who might share more recent common ancestry with this sept.

There are over 30 Meenigs or McCarthy Meenigs in the Co Cork Tithe Applotment Books (1823-1837) and hundreds in the 19th century parish registers, many in parishes close to the Cork coastline. Various ideas have been put forward for the origin of this agnomen, which apperas now to be pronounced 'mweenogh'.  Bishop King Cormac Mac Cárthaigh of Cashel (d. 1138) was also known as Cormac Muimhneach (man of Munster); since he was almost certainly of R-L21 Group B (see above), it is conceivable that the agnomen was applied to the children of a sister or daughter in his family. However what is very interesting is that our four MacCarthys of this agnomen share the same paternal ancestry as some Moynihans and Mooneys (and a further McCarthy is found among the latter). Moynihan (also varied as Minahan) is an anglicisation of the diminutive of Muimhneach. Maonach, from which Ó Maonaigh, meaning 'descendant of the wealthy one', and then Mooney, is an Old Irish form of maoineach (pron. ‘mweenoch’). It can also mean 'beloved, treasured'. The common ancestry of all these names is (crudely) estimated as the end of the 12th century. All are tested or predicted as belonging to a subclade at the end of the sequence Z16251>A159>BY2881>BY149/Z17981>Z17982>A664>A7752

Elsewhere in R-L21 Group A, the McCarthy name has clearly replaced other Munster names in the paternal ancestries. Thus twice a McCarthy appears close to Daly clusters, although one of these has yet to be verified. The Dalys were the hereditary poets or bards to several illustrious families, including the McCarthys.

Two McCarthys (in one case in fact a family of them with common 18th century ancestry) share O'Donoghue origins (sheet 9 of the tree), one O'Keefe origins (sheet 11 of the R-L21 Group A tree) and one Toomey origins (sheet 12).  It is fascinating to find one McCarthy sharing ancestry very likely to be 2nd millenium with the McAuliffes (sheet 4), even though these McAuliffes do not align with the relationship to the McCarthy kings of Cashel suggested in the histories.
There are several references in the literature to O'Donovans origins in the Uí Chairpri Aebda, claimed to be a division of the Uí Fhidgeinti, as already mentioned. Most O'Donovans form a large cluster under SNP Z16259 in a subclade of SNP A88, and in the midst of these is found a McCarthy Brogach (sheet 6). Consistent with popular belief in West Cork, the name Hayes is also seen in a definitive subclade of the O'Donovans. Also very stongly represented under Z16259 are O'Regans, in fact over 50% of the more than 40 O'Regans who have tested. Given that this name is heterogenetic, the numbers found under Z16259 are remarkable. In the literature a Munster source of the name is suggested as a (paternal) nephew of Brian Borumu. There is as yet no genetic evidence at all for this as his progeny would certainly be Irish Type III. It appears instead that the origin of these Z16259 O'Regans is a 9th century Riacán, referenced in the Annals of Innisfallen as of the Uí Chairpri Aebda. This is supported by their common ancestry with the O'Donovans at about this time.The writer's own McCarthy family is embedded in this large O'Regan cluster. A clue here to the acquisition of the McCarthy name may lie in the late 16th century writing of Florence MacCarthy Reagh claiming that the O'Regans were his kinsmen; again, did a female of his family at sometime previous to that marry an O'Regan and the sons take the McCarthy name of their mother? 
gnomina (agnomens) / branches identified as pertinent to R-L21 Group A:  Brogach, Cnoic, Cruig, Glas, Guideach (Gaibhdeach), McAuliffe MacCarthys, Muineagh.

R-L21 GROUP B:  SNP Sequence R-L21>DF13>DF21>FGC3213>Z16532>Z16526>P314>L362>ZS4606

The arguments for this being the Y-DNA signature of the progeny of the eponymous Cárthach are presented in Summary of Findings above. Fortunately, four of the mutations from SWAMH which contribute to the R-L21 Group B modal haplotype fall within FTDNA’s Panel 1 set of DYS locations (i.e the first twelve), so that the cluster was identifiable by the original Administrators of this McCarthy Surname Study in 2004. However the added bonus of the lineage having its own specific SNP, R-P314 (aka P314.2) was only discovered through a “R-L21 Walk through the Y” (WTY) test late in 2009. Then late in 2010 a further, younger, SNP in this lineage, R-L362, was also incidentally discovered in the FTDNA laboratories in two samples, one of which belonged to a McCarthy member. (Incredibly SNPs P314 and L362 are only 40 bases away from one another on the Y-chromosome, which is indeed how L362 was discovered. They are in a 'volatile' area, and have thus been found to be recurrent, i.e they have occurred elsewhere on the human phylogenetic tree, but nonetheless they are reliable indicators in the haplogroup of R-Z16526).   Finally, Big Y testing of an L362 Callahan late in 2015 revealed the sought after SNP for which he tested negative but all McCarthys have tested positive: ZS4606.  (In the same category were ZS4608 - in the DYZ19 (125 base pair repeat) region of the Y-chromosome where identification of possible SNPs is considered questionable by some - and an SNP nominally at position 21957893 (referenced to Human Chromosome Build 38, hg38) in a palindromic region, also not verifiable by individual testing).

More recently NGS testing (Big Y) has identified SNP Z16526 as a more suitable headline SNP for this lineage, thus the R-P314 Haplogroup project name change.

The R Z16526 & Subclades Project, to which all R-L21 Group B McCarthys who have tested 37 STRs or more are joined, provides analysis of the overall Z16526 tree structure, (ref. ), the tree itself being maintained at The subgroups B1, B2, B3 and BX in the McCarthy Study correspond to subgroups 3b1, 3b2, 3b3 and 3bx in the R Z16526 & Subclades Project. Subgroup B3 has been further subdivided.

Between SNP Z16526, which occurred at some time within the first half of the Irish Bronze Age, and SNP ZS4606 which occurred 2,000 - 3,000 years later, there appear to be several 'bottlenecks' in the ancestry of this group. The surnames Driscoll and possibly Crowley are found between the last two of these bottlenecks, implying that the lineage was very likely located in Munster before the time of Ceallachán (d. 954). However, upstream of these bottlenecks (and testing negative for SNP L362) are to be found subgroups of further Munster names (e.g. Leahy, Lyons, Kennedy, O'Meara) alongside subgroups with a more northerly association: surnames from the midlands and north of Ireland such as Higgins, Ogan and Heaney, some with a strong Scottish connection (Chisholm and McAlister), then Eubanks (and variants), associated with Westmoreland (now Cumbria) in N.W. England or possibly elsewhere in England. All these subgroups share ancestry with one another at a later time than they share it with the L362 McCarthys and O'Callaghans.This may be better understood with reference to the key diagram at the foot of sheet 1 of the Z16526 / McCarthy R-L21 Group B tree, but it is important to understand the application of Note 2 to the timeline provided on the diagram

SNP ZS4606 may have occurred in Cárthach's father, Saorbhreathach (= Justin), in Cárthach himself, ever increasingly less likely, up to four generations later. After this, all surnames on the tree other than McCarthy (and variants) are considered as NPEs. Some of these may be indicative of the areas which McCarthys had colonised, e.g. O'Shea in N W Cork or Kerry, O'Mahony in West Cork.  SNPs A5813 and ZS4598 are mutually exclusive and, as stated in the above Summary of Findings, it appears that SNP A5813 marks the MacCarthy Mór/ Muskerry / Duhallow branch derived from Cormac Fionn and ZS4598 the MacCarthy Reagh and Sliochd Feidhlimidh one from his brother, Donall Gott, both of whom were born late in the 12th century A.D.

To interpret the results of Y-DNA testing for our R-L21 Group B members it is necessary to reference Fig. 2 at It is possible this has errors owing to inaccuracies in the sources, and certainly not all personnages, whether recorded in the sources or not, are shown. But it serves as a basis against which we will try to align the Y-DNA test data.

R-L21 Group B1

Until November 2018, every R-L21 Group B McCarthy testing his SNPs (e.g via Big Y-500) was positive for SNP ZS4606 then one or the other of A5813 and ZS4598. Then came the long awaited result of a participant who was negative for both of these, but still positive for SNP ZS4606. He was also negative for the DYZ19 SNP ZS4608 (see above) and did not have the STR mutations at DYS557 and FTY394 (a Y-500, or FTDNA ' Panel 6' mutation) hitherto seen alongside SNPs ZS4606 and ZS4608. The implication is that he most likely descends via a line breaking away from that leading to Cormac Fionn and Dónal Gott Mac Cárthaigh early on in the six generations between Cárthach's father (Saorbhreathach) and the two brothers; however, it is still not impossible he comes down from another brother of Cormac Fionn and Dónal Gott.

R-L21 Group B2: The MacCarthy Mór Line

Since only about 5% of M(a)cCarthys are tested or predicted positive for SNP A5813, when a claimant to, or suspected descendant of, one or another ancestry supposedly coming down from Cormac Fionn is found from testing to be among this 5%, it has seemed reasonable to provisionally assign his specific genetic profile to that ancestry. This is how SNPs A9070 and A10865/65, and SNP A21813 tentatively, have been aligned in Cormac Fionn’s progeny in Fig. 2.

It will be noted from the R-L21 Group B tree that four independent subclades under A5813 have now been positively identified, two of which, those headed by SNPs A9070 and A21813, have five or more members and further genetic substructure identified (i.e. further branching of the tree), while the other two have a single M(a)cCart(h)y member each.

SNP A5813 and / or the back mutation (from 25 to 26) at DYS 447could have occurred in Cormac Fionn himself, but, with reference to Fig. 2, the considerations below suggest that these two mutations could not have occurred later than in the further Cormac (1271-1359, the purported founder of Muckross Abbey, near Killarney) and most likely occurred no later than in his father, the Donal Oge who died c. 1206. (An average rate of occurrence of mutations would have these two mutations occurring over a span of three or four generations; but mutations occur randomly and we cannot base alignment on such a premise). The ancestries of our R-L21 Group B2 members diverge after this point as follows:

(i) The owner of kit 312546 has no knowledge of his Irish origins so the progenitor of his line is any more recent than Cormac Fionn not assigned to the others!

(ii) The owner of kit 469541 has inherited much material tracing his ancestry back through the MacCarthys of Muskerry. The ancestry of this MacCarthy sept is well documented from the time of the creation of the first Lord of Muskerry (Dermod Mór Mac Cárthaigh) in 1353, and among the papers held by our member is a family tree initially drawn in 1762 showing his descent from a cadet branch initiated in the 16th century.  This is not irrefutable proof for aligning the two of his SNPs, A10864 and A10865 (which have also been found in a Kelley family in USA) with origin in the Lords of Muskerry, but as implied above provides a placeholder around which other parts of the jig-saw might be fitted. 

(iii)  A large and diverse subclade (subgroup), headed by SNP A9070, accounts for over 50% of our tested or suspected A5813 members. One of these, born in Ballyvourney, close to the Cork / Kerry border had family lore of descent from the MacCarthy Mór sept. No doubt many such stories were handed down in the families of emigrants to foreign parts, but here being among the 5% who do qualify to lay claim to such an origin and with his family rooted in such an area, the claim is given more credence. Latterly this has been significantly bolstered by the testing of a member of Samuel Trant McCarthy's wider family, which, according to Samuel’s own thorough research and family tradition recorded in his book The MacCarthys of Munster (which has contributed substantially to the construction of Fig. 2), descended from the Sliochd Cormac of Dunguile. He too was found to be positive for SNP A9070. This suggests an alignment with SNP A9070 having occurred in the senior MacCarthy Mór line, no earlier than in Dónal Mór (king of Desmond 1359-1390). However, while the size and diversity within this subclade may also appear to justify the placement of A9070 in Dónal Mór or one of his immediate progeny, it has to be remembered that there is a bias here due to the greater availability of information on this line.

(iv) A relatively substantial subclade headed by SNP A21813, with five independently tested members. One of these (the owner of kit 510546) has circumstancial evidence of a connection with the MacFinghin MacCarthys of Ardtully, namely that the earliest generation of which details are known to his family lived close to Ardtully (near Kenmare) and had a Randal MacCarthy among its numbers, a name subsequently favoured in the senior line of MacFinghin MacCarthys of Ardtully. Old genealogies link this line to Dermod of Tralee (so named simply because that was where he was killed in the 1320s). The evidence for connection of this line from the 16th century back to a specific member of Cormac Fionn’s progeny in the 14th appears to rely on a pedigree found in the Royal Irish Academy which had been created around 1600 (unless it is that research of contemporary documentation has not been sufficiently thorough!). Provenance in this Dermod would of course also fit neatly in the alignment scheme alongside the considerations of (ii) and (iii) above, but so would provenance in, for example, the Lords of Duhallow or the Lords of Cosh Maing. A second member of this group – the owner of kit 771230, with a shared phylogeny with that of kit 510546 perhaps down into the 16th century -  traces his recent ancestry to Cahirciveen, close to Ballycarbery Castle, believed to have been built by Tadhg na Mainistreach or one or more of his sons. At what stage and from where the MacFinghin MacCarthys migrated to the Kenmare area is not known to this writer!

The above depicts a cosy alignment with genealogical tracts, as shown in Fig. 2, although the apparent absence of progeny of a number of lines coming down from Cormac Fionn (with the single exception of the owner of kit 312546, (i) above) and the apparent substantial progeny of Dermod of Tralee are striking; but renowned septs may have 'daughtered out' and junior members of families not recorded in the histories may have had vast male progenies: we certainly cannot expect the numbers of male descendants of septs today to be proportional to the numbers cited in contemporary histories relating to their 14th century origins. Or maybe our sample size is just not large enough yet to draw conclusions. One further result in this R-L21 Group B2 group warns against jumping to conclusions too early.

If the 'historical tree' is correct and the alignments so far are valid, we would expect the progeny of other sons of Cormac (1271-1359) to be negative for both A9070 and A10864/65. However also found positive for SNP A9070 - and, based on STR mutations, possibly with a closer proximity genetically than any of the A9070 cluster to the Sliochd Cormac of Dunguile representative - is one of our two participants representing the sept of the MacCarthys of Ardcanaght, the owner of kit 639321 and author of the story of this family for which a link is provided in the Scholarly Articles, Presentations etc.section at the foot of our Wordpress website. (The second member of this Ardcanaght family, supposedly sharing 18th century ancestry, is found in our R-L21 Group A, with the implication of an NPE in his descent which is suspected as having occurred early on). This sept is claimed to have descended from the fourth son of Cormac (1271-1359), Donogh, via a branch of Donogh’s progeny known as the Sliochd Finghin Dubh, although it is understood one source (as used in the story) gives the progenitor, and again fourth son, as a second Donal. As with the MacFinghin MacCarthys of Ardtully, the descent between the 14th century and late 16th century appears to rely on a single pedigree. The simplest conclusion would be that the origins of this sept are incorrectly attributed and that its true provenance lies in a descendant of, say, Tadhg na Mainistreach, but an alternative scenario based on this not being the case must be considered.   

[This section still under development at 23 November 2018: all comments welcome.]

R-L21 Group B3: The MacCarthy Reagh / Sliochd Feidhlimidh etc. Line

There are many more participants in the SNP ZS4598 division. It appears that about half of these belong to a further subclade defined by the palindromic SNP ZZ50. Until recently this has only been identifiable in NGS tests such as Big Y; however it is now also identifiable using the different technology of the R1b-DF21 SNP Pack Test. We can begin to calibrate this part of the tree using the well-documented relationship of McCarthy Rabagh to its parent Reagh (Riabhach) sept. In addition there appears to be a well-defined tree substructure, in part supported by SNP Z29544, involving a number of participants with roots close to Dunmanway, i.e in the vale of Gleannacroim. Both of these lines are positive for SNP ZZ50. A mutation frequently found among those who are negative for SNP ZZ50 is a loss of one STR motif at DYS 485 (reducing from 15 to 14). Mutations at this locus are uncommon, and it is tentatively proposed that this mutation defines one particular lineage; unfortunately there does not seem to be an SNP occurring side by side with this STR mutation, that would have made an irrefutable case. The speculative conclusions are (with reference to the R-L21 Group B tree and Fig. 2) as follows:

(i) SNP ZS4598 occurred in Dónal Gott himself.

(ii) SNP ZZ50 occurred in Dónal Gott's son Dónal Maol or his grandson Dónal Caomh.

(iii) A 38 to 37 mutation occurred at CDYb in either Dónal Caomh's son Dónal Glas or his grandson Dónal Reagh (the 'founder' of the Reagh dynasty). Since CDYa/b have the highest mutation rates of all STR sites (with a frequency some suggest as averaging once in thirty generations), they can more readily be surmised as having occurred anywhere on the tree, and mutations and subsequent back-mutations here could feasibly occur without detection, so this is a particularly risky supposition; however, it appears to fit the facts.

(iv) The lineages for which SNP ZZ50 is negative represent the progeny of sons of Dónal Gott other than Dónal Maol, or of brothers of Dónal Caomh (of which there may be more than shown in Fig. 2). Of these Clann Tadhg Ilen (aka Tadhg Dall) was reported to be widespread and wealthy and on the basis that its posterity persisted the aforementioned group with a mutation at DYS485 is tentatively aligned with this, although this has to be regarded as unproven for now.

(v) The path leading to SNP Z29544 is a descent from Cormac Donn (d. 1366). He is recorded as having eight sons, one of whom was Feilim, from whom Daniel MacCarthy Glas's Sliochd Feidhlimidh of Gleannacroim (see (vi)). It is feasible that the 15 to 16 mutation at DYS 534 occurred in Cormac Donn himself and that the branches below this on the phylogenetic tree represent the progeny of some of these brothers, including Feilim, and the Sliochd Feidhlimidh named for him. However, mutations at DYS 534 are quite common so showing a single lineage common to all those under it may be a fallacy. Since the whole family could have been dispersed through the area known as Gleann 'a Croim and since there appear to be no records regarding the fate of six of Feilm's brothers, we cannot be sure which branch of the genetic tree aligns with which brother.

(vi) It will be seen from
'HAPLOGROUP of R-U198' above that the lineage Daniel MacCarthy Glas believed connected himself back to Dónal Gott and beyond that to the kings of Cashel had been usurped by a DF89-carrying male somewhere before 1700. It certainly appears that Daniel's ancestors were among the last generation or two of MacCarthys occupying Togher Castle, but how far before 1700 there was an intruder into his paternal lineage we will only begin to know when a non-McCarthy shows up among the close matches to the trio of M(a)cCart(h)ys in the U198>DF89 haplogroup and all are subjected to more extensive testing (e.g. Big Y). DF89 itself is probably over 2,000 years old so we will be looking for shared SNPs far more recent than that.

Although the paternal ancestry of McCarthy R-L21 Group B is unrelated to Olioll Olum, Eoghan Mór, Conal Corc and Failbhe Flann, as all Irish genealogical tracts have hitherto stated, this does not mean that its members did not live among the Eóghanacht peoples of the Cashel region, and at some stage usurped the leadership through a perhaps illegitimate claim to the paternal bloodline of Eoghan Mór.

Agnomina identified as pertinent to Group B:  Muscraighe (of Muskerry), of Ardcanaght, Ciaragh, Farshing / Forshing (Fairsinn), Rabagh (Rabach), Tallin / Tollin, Tul(l)ach, Downing.


This group is a small subset of the original Group C having most or all of the following departures from SWAMH: DYS 390 =25, DYS 385b = 13, DYS 392 = 14, DYS 464b = 16, DYS 607 = 16, and, where tested, DYS 413a = 21, DYS 534 = 17, DYS 481 = 25 and DYS 487 = 14. These values are consistent with the “modal haplotype” known as (North-west) Irish Type I, for which SNP R-M222 is an identifying marker. In 2011, SNP R-DF23 was found to sit between R-L21 and R-M222 on the phylogenetic tree, and subsequently a further SNP, R-DF49, has been shown to be upstream of DF23 but also downstream of L21.

Several recently identified SNPs may further subdivide the large M222 group. About 7% of our members share the (North-West) Irish [haplo]Type I; five have tested (and proved positive) for M222. This modal haplotype was identified as a consequence of the testing carried out under the aforementioned Trinity College, Dublin 2003/04 project and the common ancestor in whom the last of its characteristic mutations occurred was then estimated to have lived around the time of the 5th century Niall of the Nine Hostages, in the north-west of Ireland. However, with more abundant testing M222 and development of the Irish Type I haplotype have now been established as occurring in a long bottleneck period extending through much of the first millenium B.C., with similarities to the Irish Type II haplotype of R-L21 Group A developed. So if Niall did belong to the haplogroup of SNP M222 (and its numerous equivalents - see above), he would sit on just one of their myriad subclades which flourished in the first millenium A.D. The Irish Type I haplotype is shared by about 20% of the male population of present day Donegal and in significant percentages elsewhere in the north of Ireland and southern Scotland. Its occurrence in McCarthys, and occasionally in other families of more recent Munster origin, may be attributable to a variety of causes, any of which could equally explain the presence of McCarthys in provinces other than Munster. Prior to more recent reasons for mobility, these include trading connections, hostage taking, alliances made between tribal groups, military forces not returning to their homelands and adopting local surnames  (such as remnants of Hugh O’Neill’s and Hugh Roe O’Donnell’s armies which had marched south to Kinsale in 1601), ecclesiastical obligations, or simply individuals seeking new pastures. If SNP P314.2 (see Group B above) had arrived in Munster by movement of peoples from the north / north-west of Ireland, certainly we would expect Irish Type I / SNP R-M222 to have arrived with it.

For more detailed information please refer to (and join, if you have this haplotype!) the R-M222 Project at and

R-L21 GROUP D:  SNP Sequence R-L21>DF13>L513>BY16/Z16361

A tree showing the relation of McCarthys in this group to others in the subclades of SNP L513 is provided at The subclade structure of this tree has now been confirmed by BigY testing. The postulated sequence of STR mutations also indicates how Group D McCarthys relate more recently to others at the foot of the tree. McCarthy members of our Study are found in two subclades of BY16/Z16361 as indicated for McCarthy R-L21 subgroups D1 and D2 below.

R-L21 GROUP D1:  SNP Sequence R-L21>DF13>L513>S6365>BY16/Z16361>Z16372-84 incl. and Z17910

The McCarthys in this subgroup clearly share the same ancestry as the main Kerry group of O’Sheas - those originating in the Corca Dhuibhne peoples who had occupied the shores and hinterland of Dingle Bay. These O'Sheas comprise one of four principal groupings of the name. The others, much like most of the disparate R-L21 McCarthy groups, only share ancestry with each other in the Bronze Age

For a most informative history of these Corca Dhuibhne peoples please refer to James O'Shea's article  under Clan History at .

There is one McCarthy Sowney in this group, but many more are to be found in Group F1: see below for discussion of the origin of the agnomen. His 2nd millenium paternal ancestry is shared with several of the surname Coleman.

Agnomen identified as pertinent to Group D1:    Sowney (Samhna?)

R-L21 GROUP D2:  SNP Sequence R-L21>DF13>L513>S6365>BY16/Z16361>CTS3087

As at September 2019, we have five McCarthys (six if you count the McCarter) in various further subclades under CTS3087, with multiple instances of their possibly having acquired the McCarthy name through living in close proximity with progeny of the MacCarthy dynasty at some time beyond the 11th century A.D. Their shared paternal ancestor is estimated to have lived no later than the middle of the first millenium A.D. This suggests CTS3087 had reached  - or actually occurred in – Desmond (South Munster) prior to circa 500 A.D.  The presence of a few other surnames (e.g. Brazill, Coffey, Murray) represented in, though not exclusive to, Desmond supports this.

The Begarach agnomen represented by kit 510550 is to be found in the area of Drimoleague, West Cork

Agnomen identified as pertinent to Group D2:   Begarach (formerly Bíogach)


The Z255 haplogroup is also known as that of the Irish Sea, since many of its members are found near the shores thereof. There is also a Norwegian presence, though the chronology suggests that this is due to transport of slaves taken from Ireland in Viking raids.  A tree showing the relation of R-L21 Group E McCarthys to others in the subclades of SNP Z255 is provided at The subclade structure of this tree has now been confirmed by Big Y testing. Prominent in this R-L21 Group E is the name Cremin (and variants thereof) whether as a McCarthy agnomen or in its own right. In fact the only Cremins or McCarthy Cremins found outside McCarthy R-L21 Group E so far comprise an extensive American Cremeans (and many variants) family whose Y-DNA is of the Irish Type II variety, that of McCarthy "R-L21 Group A". Their origin is postulated as being in the Uí Cruimin erenaghs of Aghabullogue, and unrelated to any McCarthys (See

Genealogy literature suggests the McCarthy agnomen Cremin (and its spelling variants) derives from a liaison (if not a marriage) between a member of the MacCarthy Reagh dynasty (a Dermod) and the daughter of an O Cruimin. However, as indicated above, the line of the Reagh dynasty is represented genetically by McCarthy "R-L21 Group B" and, so far, this has no shared ancestry with any Cremins or McCarthy Cremins in the past 3,000 years.

The tree shows a division into McCarthy R-L21 subgroups E1 and E2. This likely occurred well back in the first millenium A.D thus it appears to be coincidence that a Cremin / Crimen / Crimeen / Cremane association with McCarthys is found in both branches. Certainly any adoption of these as a McCarthy agnomen will have occurred much later.

One Group E1 McCarthy (kit 71719) shows common paternal ancestry with several of the name Cremin or Crimeen, and also a Creamer (kit 46114), a name which is known in one instance at least to have derived from McCarthy Cremane on migration from Myross Island in West Cork (it is believed) to London late in the 18th century. Cremin kit 514621 appears to share a sub-branch with 46114 Creamer.  SNP FGC39568 has tested or is suspected positive in McCarthy kit 71719, in Creamer kit 46114 and in with more than one Crimeen / Cremin but one Cremin has tested negative for this SNP. The implication is that their Cremin (and variants) name derives from a common paternal ancestor who possibly lived before the beginning of the second millenium.

Two other Group E1 McCarthys (kits 242376 and 288581) share a common possibly mid-2nd millenium ancestor, but their connection with the Group E1 Cremins is no later than 1st millenium, and, from the present-day surnames encountered, appears to lie in Co. Tipperary and its contiguous lands to the west and east.

The McCarthy Cremins in Group E2 have roots in the Drimoleague area of Co Cork. From the tree, they appear to have a strong association with the Harrington surname (as it is usually written in Co Cork), although further testing is desirable to confirm this. As was often the case, the anglicisation of gaelic sept names would align them with a similar (or sometimes not so similar) sounding English name belonging to a transplanted family. Thus Harrington is said to stand for both O hIongardail and O hArrachtain, both of which were known in Co Cork and Co Kerry.

Agnomens positively identified as pertinent to Group E:    Cremin (Crimen / Crimeen)

R-L21 GROUP F1: SNP Sequence R-L21>DF13>Z253>BY60>A495>S15280

Kits 237106 and 287045 have tested positive for the above sequence.  In view of their close-matching STR results, and more distant haplotypes of those with other surnames who are positive for SNP S15280, it is certain that the other members of this subgroup belong to the same subclade. This is the main group of McCarthy Sowneys: there is also one such McCarthy, of Kildee, Co. Cork origin, in Group D1. If the latter is not due to an NPE, such as a stepson adopting his stepfather's surname, this implies the agnomen arose independently in more than one location. This might apply, for example, if applied to distinguish a McCarthy born on 1st November (Lá Samhna), or Hallowe'en (Oiche Shamhna), or simply in the month of November (Mí na Samhna).

The homelands of the Group F1 Sowneys appear to lie in the Co. Cork parish of Caheragh, and James McCarthy has heard it mentioned, as an alternative theory, that the Sowney agnomen could derive from the Saivnose River which provides the boundary of several townlands whose occupants 200 years ago were the ancestors of present day McCarthy Sowneys.

Agnomen positively identified as pertinent to Group F1:    Sowney (Samhna?)

R-L21 GROUP F2: SNP Sequence R-L21>DF13>Z253>A17>S856>S845

The two members of this group match on 32/37 markers. Their mutations away from  SWAMH are however consistent with those of other surnames seen in the subclade indicated by the above sequence. Confirmatory testing is desirable.  

SNP Z253, common to all of R-L21 Group F, occurred about 4,000 years ago, so none of the subgroups share a common ancestor within the era of surnames.

R-L21 GROUP F3: SNP Sequence R-L21>DF13>Z253>Z2534>L226 (Irish Type III)

This is the haplogroup of SNP L226, identified some years ago as strongly associated with the McCarthys' great mediaeval rivals the O'Briens, whose homelands were within the Thomond region of Co Limerick and Co Clare. Dennis Wright has pioneered study of this subclade and his excellent website at should be consulted for further information. It will be seen there that the current estimate for the age of the most recent common ancestor (MRCA) pertaining to all with the Irish Type III haplotype is mid-1st millenium A.D. Our three members of this group appear to be of fairly independent lineages since then, but testing of all to 111 STR markers and / or determination of any more recent shared SNPs is required to estimate the time of their mutual common ancestors.

R-L21 GROUP F4: SNP Sequence R-L21>DF13>Z253>Z2534>Z2185>Z2186>L1066

This Group was previously labelled M2. L1066 is also known as CTS1202.  As indicated on the R-L21 Group F tree, these McCart(h)ys' nearest relations appear to be Coughlins, Americanised as Conklin.  L1066 is found throughout Britain and Ireland (and beyond), but the association of the Coughlin and McCarthy names suggests a Co Cork origin. The terminal SNP prediction of L1066 needs verification by one member of this subgroup, however, to properly place them in the context of their 2nd millenium Munster origins, an NGS test such as Big Y is strongly recommended. Once L1066 has been confirmed, all should seek to join also the CTS1202/L1066 Project ( ).

R-L21 GROUP G: SNP Sequence R-L21>DF13>CTS3386>CTS5846>Z17970

All but one of our members in this group belong to a McCarty family the progenitor of which was possibly born in USA. However, to date we have found no branching in his ancestry likely to have occurred in the second millennium

R-L21 GROUP H:  SNP Sequence R-L21>DF13>Z35989>FGC35995

This appears to be a relatively little populated haplogroup which has nevertheless survived to this day with several parallel strands which diverged a long time ago. The one to which our two very closely related McCarthys are predicted to belong also features a large group of the surname Rich (possibly arising from targeted testing of this surname), plus a Sheahan and a Fehily.

R-L21 GROUP J:  SNP Sequence R-L21>DF13>Z35989>S1051

The S1051 subclade is one which is marked by 9-9 at DYS 459a/b and 19-19 at YCAIIa/b (referenced in some genetic genealogical circles as a 9919 haplotype), and for most, a rare 11 to 12 mutation at DYS 640. McCarthy kit 493019 and Macarthur kit 10733 have all of these mutations and the former has tested positive for S1051 in a Sanger Sequence test. McCarthy kit 145187, currently grouped as 'R-M269 - Unassigned', may also prove to belong here with appropriate further testing. The R-S1051 Project ( provides excellent information on this haplogroup and notes a Scottish bias, with a focus on Argyllshire. Kit 10733, with present day McCarter but formerly Macarthur appears therefore to be associated with the same corruption of MacArthur on arrival in USA as is described above for the E1b1b1 McCarter etc. subgroup which has now left our project. However, the owner of McCarthy kit 493019 with a MDKA Jerome McCarthy of Ireland appears to have gained his surname in one of the several ways possible for all other McCarthy groups saving R-L21 Group B, as described under "Diversity among McCarthys" on the Background page of this website.

R-L21 GROUP K:  SNP Sequence R-L21>DF13>DF21>S5201>Z246>DF25>DF5

Although our DNA Results page shows only two members in this group, a third, with north Kerry roots, has to date taken only a Geno 2.0 test. Since this group shares origin, about 4,000 years ago, in the DF21 haplogroup with R-L21 Group B, the predicted lineages of the two Group K participants who have taken STR tests are included on the Group B tree.

R-L21 GROUP L:  SNP Sequence R-L21>DF13>DF21>Z3017>Z16267>Z3000>Z16270

The haplotype of this group has a null value at DYS 425. This is also found in one or two other locations, e.g in the haplogroup of E1b1b1, but here in conjunction with alleles of 9 at both DYS 511 and DYS 505 it is associated with the haplogroup of R-Z3000 and the mid-first millenium Clan Colla (of the kingdom of Airgíalla), of which the Z16270 subclade is just one branch.  One participant descends from the MacCarthys of the Glanerought area (around Kenmare) while a second has associations with Springhouse (Bansha, Co. Tipperary). The MacCarthys of Springhouse are well-documented as a MacCarthy Reagh line, the paternal origins of which have been identified above as R-L21 Group B3. If our McCarthy member is truly a representative of this family it will be interesting to reveal at what stage in his paternal ancestry the NPE occurred, i.e. before, in or after the first McCarthy owner of Spring House, Denis, buried 1713 at Bansha.

HAPLOGROUP OF R-M269 - Unassigned

This group currently comprises 17 further participants (not all in the FTDNA Study and three of whom are very recently related to one another).

As the numbers in each of these clusters are small, there may yet prove to be further identifiable independent lineages each with a common ancestor who lived before surnames were introduced in Ireland. Certainly determination of terminal SNPs is necessary for this Group. 

Text by N McCarthy



The following is retained verbatim - even though reference numbers “#n” no longer have any meaning - to demonstrate the very significant early analysis by the original Administrators of this project, the first to identify what later became known as the "Irish Type II" and “P314.2” modal haplotypes.

As of October 31, 2004, there are results for 32 men comprising twenty-four unique twelve marker strings. There are four men who match exactly for 12 out of 12 markers, another three who match exactly for 12 out of 12 markers, and a third group of three pairs of men who match exactly for 12 out of 12 markers. There are 19 additional unique 12 marker strings.

Unique Y-DNA12 marker strings: 24 Result Strings Count


13 23 14 11 11 14 12 13 13 13 13 28   4

13 23 14 11 11 14 12 13 12 13 13 28   3

13 23 13 11 17 17 11 12 14 13 11 30   2

13 24 14 10 11 15 12 12 11 13 13 29   2

13 24 14 10 11 16 12 12 11 13 13 29   2

13 24 14 11 11 14 12 12 11 13 13 29   1

13 24 14 11 11 14 12 12 12 12 13 28   1

13 24 14 11 11 14 12 12 12 13 13 29   1

13 24 14 11 11 14 12 12 13 13 13 29   1

13 24 14 11 11 15 12 12 11 13 13 29   1

13 24 15 11 11 14 12 12 12 13 13 29   1

13 25 14 11 11 13 12 12 12 13 14 29   1

13 25 14 11 11 14 12 12 11 14 13 30   1

13 25 14 11 11 14 12 12 12 13 13 29   1

14 24 14 10 11 14 12 12 11 13 13 29   1

13 23 14 11 11 15 12 12 12 13 13 29   1

13 23 14 11 11 15 12 12 13 13 13 29   1

13 23 14 11 11 15 12 13 13 13 13 28   1

13 23 15 11 11 14 12 13 12 13 13 28   1

13 24 13 10 17 18 11 12 13 12 11 29   1

13 24 14 10 11 13 12 12 12 13 13 29   1

13 24 14 10 11 14 12 12 11 13 13 29   1

13 24 14 10 11 14 12 12 11 13 13 30   1

13 23 14 10 11 15 12 12 11 13 13 29   1


As the number of our study’s participants climbs into the thirties, we can begin to see some patterns emerging from the results. Two distinct groups of McCarthys can be clearly defined and a third group, less well-defined, may become apparent in time. Since the majority of our participants have ancestry that hails from Co. Cork in Ireland, more genealogical information is needed to discern possible geographic locations associated with the two defined groups.

Group A is characterized by these four traits: - a 24 at DYS447 - a 10 at DYS391 - an 11 at DYS439 - a mutation (either a 15 or 16) at DYS385b. I would include in Group A, the following participants: (#8) and (#9) who we know to be related; (#11), (#12), and (#24). I would also include in this group (#27) and (#15) even though they do not possess the mutation at DYS385b. Further testing might put (#5) in this group, as well, if DYS447 proved to be a 24.

Group B is defined by these traits: - a 13 at DYS388 - a 13 and 28 at DYS389i and DYS389ii - a 23 at DYS390 - a 16 at DYS464c. In addition, a sub-group of Group B has a 13 at DYS439 and a different sub-group has an 18 at DYS458. I would include in Group B, the following: Sub-group B1: (#31), (#18), (#7), (#14), and (#29); Sub-group B2: (#1), (#4), and (#23). I believe (#16) belongs in Group B, but is not in either sub-group.

Of the dozen participants that don't fit into either Group A or B, about 8 show some similarities which may indicate a third, nebulous Group C. However, the only trait that all in this group have in common is some kind of mutation at DYS449. Otherwise, they all appear to be very closely related to the Atlantic Modal Haplotype, which is most prevalent in Haplogroup R1b. The similarities might simply be random, given the close nature of all those in Haplogroup R1b. Participants who might be included in this group include (#2), (#3), (#19), (#20), (#21), (#22), (#25), and (#26). Further testing is needed to determine whether this really is an identifiable group or just a collection of similar samples. Two other participants, (#30) and (#6) matched each other pretty closely, but they don't fit too well into either of the defined groups, although there are some similarities to Group B. More testing is needed on (#30) to see if it truly matches with (#6) at more points.


In recent weeks, exciting new data has shown that there is a group of McCartys whose DNA results are significantly different from the early participants. These three participants have results that belong, not to Haplogroup R1b, but to Haplogroup E3b, which evolved in the Middle East and northern Africa. Two participants (#32) and (#34) can trace their ancestry to the same region of South Carolina. These participants were not sure of a ancestral connection until their results showed a perfect 12/12 match! More genealogical research will likely show the relationship between the lines. The third participant (#13) from this group, dubbed Group E, shows results that are different from the others, but is likely related through a much more distant common ancestor.