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Calculation of Time to an MRCA for R1a1a Ashkenazi Levites


Traditionally, the time to the Most Recent Common Ancestor (the "MRCA") shared by men belonging to a Y-DNA cluster has been calculated by reference to the number of Short Tandem Repeat ("STR") mutations that are present in the cluster. More recently, Single Nucleotide Polymorphisms ("SNPs") have been used to calculate the time to the MRCA of men belonging to a Y-DNA cluster.

As shown below, use of these methodologies can yield varying results, depending upon, among other things, the mutation rates that are used and the pool of men for whom test results have been received. STR-based analyses have suggested a time to an MRCA for R1a1a Ashkenazi Levites of about 800 to 1,500 years; SNP-based analyses have suggested a time to an MRCA for R1a1a Ashkenazi Levites of about 1,500 to 2,500 years.

Note that the time to an MRCA should be adjusted by taking into account the average age of men who have done Y-DNA testing. Doing so will add about 50 years to the time to an MRCA.

Calculation of Time to an MRCA Based Upon STRs

By considering the number of STR mutations that are present in a Y-DNA cluster, the number of STR markers tested, and the mutation rates of STR markers, it is possible to calculate how long ago the MRCA of the tested men lived.

The accuracy of such calculations will depend in large part upon whether the test results are from a representative group of men. Furthermore, to the extent that a cluster includes a large group of men who share a relatively recent MRCA and only a small group of men with a more distant MRCA, calculations will underestimate the time to the cluster's MRCA.

Third-Party Calculations of Time to an MRCA Based Upon STRs

According to a 2012 article by Rozhanskii & Klyosov on the R1a haplogroup, the “large Jewish R1a1a-L342.2 branch” “descends from a common ancestor who lived only 1300 ± 150 ybp [years before present].” I. Rozhanskii & A. Klyosov, Haplogroup R1a, Its Subclades and Branches in Europe during the Last 9,000 Years, Advances in Anthropology, Vol. 2, No. 139-56 (2012)

In an April 2014 article posted here, Klyosov calculates, based upon the same methodology and a set of 179 67-marker haplotypes for R1a1a Ashkenazi Levites, that the MRCA for R1a1a Ashkenazi Levites lived 1,250 years ± 130 years ago. In the same article, using a spreadsheet that calculates time to an MRCA based upon marker-specific mutation rates, Klyosov calculates a time to an MRCA of 1,123 years ± 168 years ago. As Klyosov notes, both time frames are consistent with that calculated by Rozhanskii and Klyosov in their 2012 article, based upon a smaller number of haplotypes.


Calculations of Time to an MRCA Based Upon STRs Compiled for This Website

As noted above, the accuracy of the calculation of time to an MRCA will depend in large part upon the representativeness of the sample of the men whose test results are considered.

The group of R1a1a Ashkenazi Levite men who have tested to 111 markers appears to be more closely related than the group of men who have tested to 67 markers (perhaps because men with close matches at 67 markers are more likely to have upgraded their test results to 111 markers than are men without close matches).

As a result, a time to the MRCA for R1a1a Ashkenazi Levites calculated based upon test results at 67 markers is more likely to be accurate than one based upon test results at 111 markers; conversely, a time to the MRCA for R1a1a Ashkenazi Levites calculated based solely upon test results at 111 markers is likely to understate the time to an MRCA. Accordingly, this website calculates the time to an MRCA based upon results at 67 markers.

Sidney Sachs, project administrator of the Y-Haplogroup J2b_445-8 Project, calculates about 800 years (28 generations at 28.8 years/generation) to an MRCA based upon the 37-marker results reported on this website as of December 20, 2013, using the rates that Dr. John Chandler reported in J. Chandler, Estimating Per-Locus Mutation Rates, Journal of Genetic Genealogy 2:27-33, 2006 as applied to a genetic distance of 326 steps over 1,388 marker values at 37 markers (yielding a mean value of 4.26 (1388/326)). Using the same methodology, Sachs calculates about 835 years (29 generations at 28.8 years/generation) to an MRCA based upon the 67-marker results reported on this website as of December 20, 2013, also using the rates reported by Chandler.  


Wim Penninx, in his calculation of time to an MRCA for Y-DNA branches of Ashkenazi Jews, estimates that the MRCA for R1a1a Ashkenazi Levites lived in about 752 to 900 CE, based upon his analysis of 192 R1a1a Ashkenazi Levites at 67 markers. For this website, he has calculated that: (1) the MRCA for Y2619+ Y2630+ R1a1a Ashkenazi Levites lived in about 950 to 1120 CE; and (2) the MRCA for Y2619+ Y2630- R1a1a Ashkenazi Levites lived in about 650 to 885 CE. He has also calculated the time to an MRCA for three separate clusters of Y2619+ Y2630- R1a1a Ashkenazi Levites identified elsewhere on this website: (1) the MRCA for Y2619* Tentative Cluster A lived in about 740 to 1192 CE; (2) the MRCA for Y2619* Tentative Cluster B lived in about 892 to 1169 CE; and (3) the MRCA for Y2619* Tentative Cluster C lived in about 920 to 1560 CE (the broader time range for this cluster reflects the small sample size).

Calculation of Time to an MRCA Based upon SNPs

In their 2013 paper analyzing the SNPs of R1a1a Ashkenazi Levites, Rootsi & Behar state that "the tight cluster of Askhkenazi Levite R1a-M582 haplotypes strongly indicates a recent origin from a single common ancestor who, according to our provisional dating, lived" about 1,500 to 2,500 years ago.

As discussed in more detail here, Michał Milewski has estimated that the R1a1a Ashkenazi Levite common ancestor lived about 1,500 to 1,700 years ago, based upon the initial results of full Y-DNA testing through Full Genomes Corporation and Family Tree DNA's Big Y test and analyses of R1a1a Ashkenazi Levites whose Y-DNA was sequenced as part of scientific research.  
 
CochinLevite.1774.trim
Engraving by Charles-Nicolas Cochon, from: Michel-François Dandré Bardon,
Costume des anciens peuples (Paris: 1772-1774), vol. 2 (1774)
Costume of the Levites (based on Calmet)