McCARTHY y-DNA STR ANALYSIS, AND COMPARISON WITH OTHER IRISH RESULTS

1.   Introduction

This page presents a simplistic analysis of McCarthy STR results taken from several sources and compares them with the Irish Heritage DNA Project (IHDP, now Ireland yDNA) data as at October 2008 for non-McCarthys*. It does not pretend to be an authoritative statement on the subject, but it is hoped that it will be of service to the members of the McCarthy Surname Study. It should be read in conjunction with McCarthys in Antiquity on the Project Background page, at: www.familytreedna.com/public/McCarthySurnameStudy/default.aspx. Some background information is also given for the benefit of those fairly new to the subject.

The non-McCarthys are divided into two groups as determined by the location indicated for the earliest known ancestor of the contributors to the IHDP: Munster (whence it is expected most if not all McCarthys also came), and non-Munster (or rest of Ireland). Much of the data was originally generated by the Trinity College, Dublin, Irish DNA project of around 2003/04 by Prof. D G Bradley and B McEvoy. A total of 4,487 records have been used, of which 4,325 are non-McCarthy: these divide as 1,050 from Munster and 3,275 from the rest of Ireland. While there will certainly be some inaccuracies in these provenances, and of course they take no account of previous movement within Ireland, they are considered representative enough for this coarse assessment.

The McCarthy records are derived from:

(a) The aforementioned Irish Heritage DNA Project website.

(b) The FTDNA McCarthy Surname Study y-DNA Results page (as at January 2010).

(c) Three Ysearch entries which were not found in (b). (There may possibly be more of these).

(d) The Ybase website (as at March 2008).

Elimination of obvious duplicates and McCarthy Surname Study records which do not relate to a McCarthy male line left 162 McCarthy results for the analysis.

* DYS 460 was not reported at this time. The non-McCarthy data for this marker does not distinguish Munster from non-Munster provenance. They have been taken solely from the records for predicted or tested haplogroup R1b and its subclades in the y-DNA Results table in the Ireland y-DNA Project pages, as at March 2010.

2.   Use and validity of data

The data presented in Table 1 below do not separate out results which SNP testing or prediction indicates belong to haplogroups other than R (principally subclades of haplogroups E, I and J), although it is recognised that the SNPs giving rise to these haplogroups occurred before Western Europe was colonised and that their inclusion may mask to some extent any differences sought between the three datasets examined. The R1b haplogroup (frequently identified as its R1b1b2 subclade) dominates all three datasets (81% of non-McCarthys and 91% of McCarthys). It is intended to produce a similar comparison restricted to tested or predicted R1b members of these sources later. In the meantime, some selected analysis specific to R1b* (i.e samples tested or predicted as haplogroup R1b and all subclades thereof), is offered in section 6 below.

While the number and geographical distribution of non-McCarthy records is probably sufficient to provide a country or province-wide representative sample, it is acknowledged that the 162 McCarthy results are too few to be a representative sample of all McCarthys. And, with a few exceptions, these reduce to 67 samples where 25 markers have been tested (FTDNA's "Panels" 1 and 2), 47-50 where approximately 37 markers have been tested (FTDNA's "Panels" 1, 2 and 3) , and 18 or 19 thereafter. But until many more McCarthys add their data to the FTDNA or other public databases, it is the best we can do! One obvious skew occurs where a number of people from a single community have been tested in pursuit of sorting out local genealogy and have been found to share a relatively recent common ancestor (e.g the McCarty, South Carolina-Edgefield Project, which has about 26 members representing just three family groups).

3.   Base haplotypes

The most common allele count has been determined for each DYS based on all 4487 records reviewed and is identified as the modal alleles for the total record set.

Many detailed analyses of STR results have been reported on the internet by learned geneticists and mathematicians, and these have given rise to some nominal base haplotypes - defined by similar sets of modal alleles - for population groups of western European and / or Irish men. It is surmised that these existed at some stage between about 800 and 5,000 years ago, as described in section 4 of McCarthys in Antiquity. They all appear to be associated with subclades of haplogroup R1b1b2, characterised by SNP M269, which is calculated as being about 10,000 years old. However, it is likely that Ireland 2,000 - 3,500 years ago was also populated by men of haplogroups other than R, and indeed their ancestors are likely to have been in the country before the (new?) wave of R1b1b2 immigrants arrived. While these base haplotypes do not carry the definition of SNPs, attempts have been made (by geneticists) to calculate the approximate time at which they became evident and to match them to SNPs believed to have occurred in progenitors of the same groups. Individuals will, of course, today normally carry some later STR mutations which distinguish them from one another within these groups.

The earliest of these base haplotypes was a 6-marker Atlantic Modal Haplotype (AMH) proposed by population geneticists. In due course this developed into the 67 marker Super Western Atlantic Modal Haplotype (SWAMH) defined by Whit Athey on the basis of analysis of R1b haplogroup results. (See www.hprg.com/R1b). Subsequently, (North-west) Irish Type 1, (South) Irish Type II, Irish Type III (Dalcassian) and Irish Type IV / Continental base haplotypes have been proposed (see again McCarthys in Antiquity). Table 1 provides, as reference for comparison with the modal alleles determined in this study, the modal alleles for each of these base haplogroups as indicated in Ysearch under the following User IDs indicated. (Alternatives showing some variation may also exist in Ysearch). 

 The set of modal alleles generated from the 4487 records almost perfectly matches the SWAMH and the Klyosov Irish L21 haplotypes, the differences being as follows: 

In each of these three cases, the Klyosov Irish L21 base haplotype occurs almost as frequently as the modal allele in the overall 4487 record set. Note too that at DYS 534, although all three of the tabulated haplotypes match, there are 274 records with a 15 allele count and 273 with 16 among the records analysed.

4.   Mutation Rates

Mutations in STRs are much more common than SNPs. STR average mutation rates of the order of 0.003 (1 in 333 generations) per DYS per generation have been suggested in various papers, with so-called fast-moving mutations having two, three or more times this rate and slow-moving ones possibly as little as 1/20 of this rate. Average mutation rates for each DYS marker remain a subject of conjecture and debate, but there is general accord as to which tend to mutate less frequently and which more frequently. For further information on this subject see, for example, Marker and Mutation Comparison on this website and the online Journal of Genetic Genealogy article at www.jogg.info/32/editorial.htm   Based on these references, Table 1 indicates DYS mutation rates as S (slow), VS (very slow), M (Medium), F (fast) and VF (very fast).

The prevalence of certain mutations within a haplogroup in one surname or family group or another, if identifiable, may thus be an interim substitute for identifying specific population groups pending the discovery and irrefutable placement on the phylogenetic tree of SNPs which have occurred in the past few millenia. In this respect, these are particularly valuable where they are slow-moving mutations, whereas when sorting out recent ancestry, the faster-moving ones are or more use. But it should still be remembered that, even with the slow-moving mutations, the same mutation can occur on different occasions, so STR mutations do not necessarily label an event with the same definition as SNPs.

5.   Presentation of data

For each DYS value, the number of modal, modal +1, modal -1, modal+2, modal-2, modal+3 etc. alleles has been counted for each of the record sets, which are labelled as:

1B    Non-Munster excl McCarthy

2A    Munster excl McCarthy

3      McCarthy only

The results currently presented record, in Table 1:

•  the number of results for each DYS value for each of the three datasets.
•  the percentage occurrence of the modal DYS value, greater than modal, less than modal and zero allele count for each of the three datasets.
•  the difference in these percentages between the McCarthy results and (a) dataset 1B and (b) dataset 2A.