Methodology

Y-DNA Methodology

I used the following methodology to prepare the Y-DNA trees and supporting information posted on this website in 2018. (As discussed on this page, in 2022 I refined the analysis by using Family Tree DNA's Y-DNA Discover utility to analyze further each of the Y-DNA clusters that I identified through my 2018 analysis .)

1. I used the methodology described below to identify the FTDNA-reported Y-DNA SNPs for the cohorts of Family Finder-tested men who share 100 cM, 80 cM, or 50 cM of autosomal DNA, respectively, with at least one of 25 people with four Ashkenazi grandparents.

2. Y-DNA SNPs reported by FTDNA based upon STR testing date back tens of thousands of years and are therefore of limited use in identifying the Y-DNA lines that were present in an Ashkenazi (or proto-Ashkenazi) population that dates back 1,500 to 2,000 years, or in a Jewish (or proto-Jewish) population that dates back perhaps 3,000 to 3,500 years. Accordingly, I disregarded these far-upstream SNPs when making my initial efforts to identify Ashkenazi Y-DNA lines.

FTDNA uses one to four upstream SNPs to identify the haplogroups of men who have done only STR testing. (The men whose haplogroups are identified in red text on FTDNA's project pages have done only STR testing.)

The haplogroups reported by FTDNA based on STR testing in the Y-DNA haplogroups that contain a significant number of Ashkenazi Jews are as follows:

E: E-L117, E-M2, E-M35, and E-M96

G: G-M201

I: I-M170, I-M223, I-M253, and I-P37

J1: J-M267

J2: J-M172

Q: Q-M242

R1a: R-M512, R-M198, R-Z283

R1b: R-M269

R2: R-M124

T: T-M70

3. I then used FTDNA's Y-DNA Haplotree to determine, for each Y-DNA terminal SNP identified as potentially Ashkenazi through the methodology used for this analysis, the total number of men in FTDNA's database who were, as of early January 2019, reported as "Branch Participants" for that SNP (i.e., the number of men who were reported as having that SNP as their terminal SNP).

If dozens or hundreds of men are reported as Branch Participants for a SNP, that indicates that the SNP has been reported based on STR test results, Geno 2.0 results, SNP packs, or Walk Through the Y testing, rather than based on Big Y testing. Except in rare circumstances, SNPs shared by a large number of men are likely to date back several thousands of years to tens of thousands of years, making those SNPs generally irrelevant to the analysis performed herein.

4. I next compared the number of men reported as Branch Participants for each SNP with the number of men in the sample set reported as having that SNP. For the reasons discussed below, as a general matter the men in the sample set will constitute only a proportion -- perhaps 25% to 50% -- of the Ashkenazi men who have done Big Y testing.

Thus, if about 25% to 50% of the total number of men reported by FTDNA as having a particular terminal SNP are included in the sample set (especially at 100 cM), there is a substantial likelihood that men reported with that SNP are of Ashkenazi ancestry on their direct male lines. Reference to FTDNA's Y-DNA Haplotree demonstrated that the vast majority of such men belonged to Y-DNA clusters that include multiple branches with other men in the sample set, confirming that those SNPs are commonly found in the Ashkenazi population.

Conversely, there are a substantial number of men in the sample set (especially in haplogroups I and R1b) who were only 50 cM matches for at least one of the 25 probands and who are not in the same Y-DNA clusters as other men in the sample set. There is a significant likelihood that many -- but by no means all -- of those men are not Ashkenazi (or Jewish) on their direct male lines.

Because the sample set at 50 cM is demonstrably overinclusive in this regard, I disregarded 50 cM matches if they did not belong to Ashkenazi Y-DNA clusters or were only a small percentage of the Branch Participants reported by FTDNA. As a consequence, however, some rare Ashkenazi Y-DNA lines have likely been excluded from the results reported herein.

5. Using the FTDNA Y-DNA Haplotree as of early January 2019 to identify branching, I prepared trees (linked, by haplogroup, from the left-hand column on this page) for each separate ancestral line identified through this analysis.

In most instances, the identified ancestral lines include more than one branch with a substantial number of Ashkenazi men. However, some such ancestral lines appear to include non-Ashkenazi -- and non-Jewish -- branches, in addition to Ashkenazi branches. In a few instances, the identified ancestral lines include only a single branch with Ashkenazi men in the sample set.

6. To the right of each posted tree on the pages for each Y-DNA haplogroup, I have included the data that I used in identifying likely Ashkenazi branches -- tables showing, for each SNP: (a) the SNP name; (b) the number of Branch Participants reported by FTDNA; and (c) the number of men in the sample set who match at least one of the 25 probands at (i) 100 cM, (ii) 80 cM, and (iii) 50 cM.

7. Below each posted tree, I have set forth the SNPs that are upstream from the top SNP of the tree, as taken from the FTDNA Y-DNA Haplotree. I have included the ISOGG designation for each cluster.

For certain Y-DNA clusters that are included in YFull's Y-Tree, I have set forth: (1) YFull's estimate of a time to a most recent common ancestor ("TMRCA") in years before present ("ybp"); and (2) YFull's range of time to a most recent common ancestor ("TMRCA") at 95% accuracy.

For certain Y-DNA clusters that are included in Wim Penninx' analyses at JewishDNA.net, I have included: (1) his designation for the cluster (a branch number followed by a number (e.g., AB-067), and an abbreviated SNP chain (e.g., R1a-Z93-M582)); and (2) his estimated TMRCA range stated in terms of years at 95% accuracy.

8. At the bottom of the page for each Y-DNA haplogroup, I have included a table identifying every Y-DNA SNP in the sample set that does not appear on one of the posted trees.

For each SNP that is on the Big Y tree but not on one of the posted trees, I have stated whether such SNP is upstream from SNPs found in one or more Ashkenazi Y-DNA clusters. If men who are reported based upon STR or Geno 2.0 testing as having these SNPs are of Ashkenazi descent on their direct male line, there is a high probability that such men belong to one of those Ashkenazi Y-DNA clusters. However, a large proportion of the men reported as having these terminal SNPs are not of Ashkenazi descent on their direct male lines.

I have also identified SNPs that are not on one of the posted trees but that may reflect an Ashkenazi Y-DNA line. (Such SNPs are those that are found disproportionately in the sample set, thereby indicating likely Ashkenazi origins, but are not part of an Ashkenazi Y-DNA cluster identified in the study.) Further testing is necessary to confirm whether these SNPs define Ashkenazi branches.

Finally, those SNPs that I have not identified as being upstream from an Ashkenazi Y-DNA cluster or as possibly reflecting an Ashkenazi Y-DNA line are likely not to be Ashkenazi in origin. In many instances, those Y-DNA lines appear in the sample set because of overinclusiveness in the methodology used to identify likely Ashkenazi Jews. In other instances, those Y-DNA lines may be Sephardic or Mizrahi in origin, or may have entered the Ashkenazi population in the past few centuries. It is also likely that further test results will show that a few of these Y-DNA lines are minor and/or undertested Ashkenazi lines.

mtDNA Methodology

1. I used the methodology described below to identify the FTDNA-reported mtDNA SNPs for the cohorts of Family Finder-tested people who share 100 cM, 80 cM, or 50 cM of autosomal DNA, respectively, with at least one of 25 people with four Ashkenazi grandparents.

2. The mtDNA frequencies reported by haplogroup and clade are based upon the cohort of Family Finder-tested people who share 100 cM with at least one of 25 people with four Ashkenazi grandparents.

Issues with Using Family Finder Match Lists to Determine Ashkenazi Haplogroup Frequencies

While the issues identified above create limitations on the ability to use Family Finder match lists to determine Ashkenazi Y-DNA and mtDNA haplogroup frequencies, those issues can be mitigated in large part through use of the methodology described below.

1. To address the fact that a single Ashkenazi person's Family Finder match list will fail to identify many fully Ashkenazi people (i.e., people with four Ashkenazi grandparents) who have done Y-DNA or mtDNA testing, I aggregated Family Finder lists from multiple people who are fully Ashkenazi.

For use in this analysis, I combined Family Finder match lists from 25 people with four Ashkenazi grandparents (the probands) to create a spreadsheet that includes all of their matches (for a total of 56,162 discrete persons) as of December 20, 2018. Because of the endogamous nature of the Ashkenazi population, this combined match list is likely to include almost all of the people with four Ashkenazi grandparents who have done Family Finder testing (along with many other people who do not have four Ashkenazi grandparents).

2. To address the fact that many of the people on the combined match list are likely not Ashkenazi on their direct male and/or direct female lines, I, taking advantage of the fact that endogamy results in relatively high levels of shared autosomal DNA in the Ashkenazi population, considered only those matches who share a high amount of autosomal DNA with one of the 25 probands, people who have four Ashkenazi grandparents.

For use in this analysis, I excluded from the Y-DNA and mtDNA frequency analysis any person on the combined match list who does not share a substantial amount of autosomal DNA with at least one of the 25 probands. For analytical purposes, I initially considered three cohorts of Y-DNA-tested men and mtDNA-tested people who shared at least 50 cM, 80 cM, or 100 cM, respectively, with at least one of the 25 probands:

50 cM 80 cM 100 cM

Total Tested: 37,381 26,938 21,849

Y-DNA Tested: 8,196 6,231 5,229

mtDNA Tested: 8,345 6,276 5,187

As discussed below, there is some variation in the frequencies of Y-DNA and mtDNA haplogroups depending upon whether such frequencies are considered at 50 cM, 80 cM, or 100 cM. Because people who share the most autosomal DNA with fully Ashkenazi matches are the most likely to be Ashkenazi on all of their lines (including their direct male or female lines), the percentages reported on this website are those among the 100-cM matches.

The correspondence between 100-cM matches and Ashkenazi direct male or female lines is by no means perfect -- it is highly likely that (1) some people with four Ashkenazi grandparents will have some close relatives who are not Jewish (or are Jewish but not Ashkenazi) on their direct male or direct female lines, and (2) some people with high proportions of Ashkenazi autosomal DNA will be descended on their direct male and/or female lines from ancestors who were not Jewish (or who were Jewish but not Ashkenazi) -- so it is highly likely that the percentages reported herein are somewhat skewed. (To deal with the former issue, one could use a cut-off of autosomal DNA to remove matches who are very closely related to a proband. After completing this analysis, I removed any matches of greater than 200 cM; because virtually all such persons who have done Y-DNA and/or mtDNA testing shared at least 100 cM with another proband, using the 200-cM cutoff had no appreciable effect on the haplogroup percentages reported herein.)

As discussed here, however, the frequencies calculated through this analysis are in line with those set forth in prior analyses, which tends to support the reliability of this methodology in broad strokes, notwithstanding the strong likelihood that the 25 probands have a few 100-cM matches who are not Jewish (or who are Jewish but not Ashkenazi) on their direct male or direct female lines.

3. A practical issue -- not a methodological one -- is presented by FTDNA's practice of reporting haplogroups with different degrees of generality or specificity depending upon the level of testing performed.

To address this issue, for purposes of this analysis I used the highest level of generality for most of the Y-DNA haplogroups, but broke Y-DNA haplogroup J into J1 and J2 and Y-DNA haplogroup R into R1a, R1b, and R2 to the extent that the information reported on the match lists was sufficient to allow identification of those clades. (In a few instances, I omitted test results within Y-DNA haplogroups J and R because available information did not readily allow a determination of whether the tested men belonged to J1 or J2, or R1a, R1b, or R2, respectively.)

4. This analysis does nothing to address the facts that: (1) a substantial number of the people who have done Y-DNA or mtDNA testing through FTDNA have not done Family Finder testing; and (2) most of the Ashkenazi population has not done Y-DNA or mtDNA testing through FTDNA at all.

Because of the large sample size and the lack of any reason to doubt that the people who have done both Family Finder testing and Y-DNA and/or mtDNA testing are representative of the universe of Ashkenazi Jews who have done Y-DNA or mtDNA testing through FTDNA (or of the Ashkenazi population in general), I have assumed that the frequencies reported herein are generally representative of those of all Ashkenazi Jews who have done Y-DNA or mtDNA testing (and of the Ashkenazi population in general).

Absent an easy way to identify those people who (1) may have tested the Y-DNA or mtDNA of relatives who have matching Y-DNA or mtDNA or (2) may have chosen not to test Y-DNA or mtDNA because a close relative with the same Y-DNA or mtDNA has already tested, I assumed that these two possibilities generally cancel each other out.

Similarly, because there is no way to use the combined match list to determine the Y-DNA and mtDNA haplogroups of Ashkenazi Jews who have not done Y-DNA or mtDNA testing, I assumed that the very large sample size considered in this analysis makes it likely that the samples considered herein are generally representative of the Ashkenazi population as a whole.

To the extent that, as is likely, any of these three assumptions is not fully accurate, the Y-DNA and mtDNA haplogroup frequencies reported herein will differ somewhat from the frequencies found in the Ashkenazi population as a whole.