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Y-DNA and the Clan

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All life is encoded in a biochemical code-book called DNA (Deoxyribonucleic Acid). DNA is comprised of four fundamental molecules called nucleotides called Adenine (A), Aytosine (C), Guanine (G) and Thymine (T) and these nucleotides are assembled together in a string of material which encodes genes - the things which we inherit from parent to child, generation to generation. So DNA encodes everything about us and how our bodies look, grow and function, and so there is a lot of it. Our DNA forms in groups of genetic material called chromosomes, and each chromosome contains unique genetic information for a handful of genes. Two types of chromosomes are denoted X and Y, and these two particular determine the sex of a person. Whereas the X chromosome is inherited from mother or the father (depending on the sex of the child), the Y chromosome is inherited exclusively from the father to a son. As such, Y-DNA is the DNA found in the Y chromosome and is transmitted only from father to son. This makes Y-DNA an extremely valuable tool when tracing paternal ancestry. 

Y-DNA and Genealogy

As human groups evolved and migrated over time and the continents, certain groups descending from common Y-DNA ancestors began to emerge. Today, scientists refer to these groups as haplogroups. As communities began to settle into certain regions and reproduce with each other, certain haplogroups began to become more prevalent in certain regions than other (very) distantly related cousin haplogroups.

So what makes a haplogroup different from another one?

Y-DNA Haplogroups are characterized by mutations in the Y-DNA called single nucleotide polymorphisms (SNPs). A SNP is a change in one of the nucleotides found in the genetic information passed on from father to a certain son. Since these SNPs are in the Y-DNA, they are also inherited. So where some ancestral male's DNA accidentally flipped a cytosine molecule for an adenine, so too will all of his male descendants carry that same mutation.

How do SNPs help genealogists?

Due to the structure and other mechanical and chemical properties of SNPs, geneticists can actually estimate mutation rates with pretty good accuracy. With that knowledge genetic genealogists can workout when a SNP would have mutated, and so it becomes possible (given a genealogical pedigree) to piece together which ancestor (or handful of ancestors) had the initial mutation. With more people testing for a certain SNP, and more of the same SNP being identified, we can refine our results more and more until eventually we narrow it down to one ancestor. Then we can start to determine other SNPs that emerged in the subsequent generations and we can build a table of SNP belong to a certain haplogroup descended from a common ancestor. Using this methodology we can now identify members of the McCarthy Reagh clan who cannot demonstrate traditional historiographic genealogical descent. 

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The McCarthy Surname Y-DNA Study has done tremendous work to establish exactly that, and their results (current as of January 2023) can be found here: Donal Goth's descendant Haplotree. If you haven't yet seen their extensive "Scrapbook" with all the genetic genealogy be sure to visit The McCarthy Surname (Y-DNA) Study Scrapbook page. For reference, Donal Goth (spelled Donal Gott on the haplotree) is found in the R-L21 Group B, SNP R–ZS4606, chart. 

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If you have a Y-DNA result already, the quick check is:

  1. ZS4606+ → dynastic McCarthy

  2. ZS4598+ → Reagh/Sliochd Feidhlimidh

  3. Test relevant sept SNPs found below (e.g., ZZ50, BY7779, FGC1058, etc.) to pinpoint your branch.

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MacCarthy Reagh SNPs

This listing is not all-inclusive and is a living document.

As we learn more information about MacCarthy Reagh distinct haplogroups and SNPs we will update this list.

SNP Identifier
Sept Name
Earliest Known Ancestor
Notes
ZS4598
MacCarthy Glas/Ciaragh
Donal Gott (d. 1251)
SNP ZS4598 occurred in Dónal Gott himself.
BY7779.2
McCarthy Tullagh (Tullach)
McCarthy Tullagh seems to be a sub-sept of the McCarthy Reagh of Drinagh.
BY74588
McCarthy Farshing
Daniel McCarthy Farshing born c.1730, Gortnasowney
A10926
McCarthy Tallin/Farshing
BY140627
McCarthy Rabagh
FGC1058
McCarthy Tallin
BY7779
McCarthy Reagh of Drinagh
Donal na Pipi
This sept, although centered on Dunmanway & Drinagh parish, has established a line of descent from Donal na Pipi.
ZZ50
MacCarthy Reagh
Donal Caomh, 2nd Prince of Carbery
Only McCarthy Reagh descendants can be positive for SNP ZZ50.

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The Genetics​

 

With the advancements in the McCarthy Surname Y-DNA Study we now know a good amount of identifying genetic information:

  • the SNP ZZ50 denotes descent from the earliest MacCarthy Reagh princes;

  • the SNP Z29544 appears to be unique to the MacCarthy Glas sept;

  • the SNP BY7779 is unique to the “McCarthy Reagh of Drinagh” and MacCarthy Tullagh families;

  • the SNP BY140627 is unique to the MacCarthy Rabagh Branch;

  • the SNP FGC1058 is unique to the MacCarthy Farshing and Tallin septs;

  • the SNP BY82013 is unique to the MacCarthy Tallin (Talún) sept

  • According to the Fiant of Elizabeth I (1558-1603), the MacCarthy Reagh family of Kilbrittain was being distinguished from the MacCarthy Farshing of Skate by the 16th century, so the Farshing and Tallin branches are junior to the Springhouse branch (founded in the 17th century).

 

With this information we can start to establish seniority of branches of the family:

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  1. MacCarthy Reagh progeny of Cormac and Eleanor (extinct in the male line)

  2. MacCarthy Reagh of Kilbrittain progeny of "one of the other sonnes" of Daniel MacCarthy Reagh (d. 1 Aug. 1636) (extent - includes the McCarthy families of Vancouver, Colorado, and Oak Bluffs)

  3. MacCarthy of Toulouse (extinct in the male line)

  4. MacCarthy of Springhouse (dormant, probably extinct in the male line)

  5. MacCarthy Farshing & Tallin/Talún (extent - likely descended from one of the sons of Finghin, the 10th Prince of Carbery, or from the son of Dermod, the 11th Prince of Carbery)

  6. MacCarthy Rabagh (extent - descended from the 7th Prince of Carbery)

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Works Cited

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  • Ginnell, L. (1894). The Brehon Laws: A Legal Handbook. T. Fisher Unwin. 

  • Keane, L. M. (2014, May). Irish Chiefly Succession in the 21st Century. Kingdom of Desmond Association. Retrieved April 25, 2023, from https://kingdomofdesmond.com/?page_id=331 

  • Laine, P. L. (1839). Généalogie de la Maison de Mac-Carthy anciennement Souveraine des Deux Momonies ou de l'Irlande Méridionale. Retrieved April 25, 2023, from https://celt.ucc.ie/published/F830000-001.html.

  • Morrow, J. J. (2021, December 16). Guidance Note, Chiefs of Clans and Families, Succession of Chiefs, Family Conventions, Nomination of Heir. Retrieved April 26, 2023, from https://courtofthelordlyon.scot/SuccessionofChiefsGuidanceNote.pdf 

  • O'Curry, E. (1996). On the Manners and Customs of the Ancient Irish: A series of lectures. (W. K. O'Sullivan, Ed.) (Vol. 1). Éammon de Búrca for Edmund Burke Publisher. 

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