Sephardic DNA testing has become a valuable tool in genealogy, and a frequently misunderstood one. This page summarises what the different kinds of test do, the main scientific effort to map Jewish lineages, and what that work has contributed to Sephardic family history.
It reports the findings of the researchers who have presented to Sephardic World, and does not go beyond them.
The three kinds of DNA test
There are three tests used in genealogy, and they answer different questions. The distinction, as Adam Brown has explained it, is one of how much information each carries and which line of ancestry it follows.
Y-DNA
Y-DNA is passed from father to son, largely unchanged, and so traces the direct male line. That is the line a surname usually follows. Only men carry it.
Because it is not diluted from one generation to the next, it can reach back thousands of years. With modern testing covering millions of positions, it carries enough detail to date and place events far back in a family’s past. It is the test best suited to studying the deep origins and migrations of a people.
Mitochondrial DNA
Mitochondrial DNA, or mtDNA, is passed from a mother to all her children, but only daughters pass it on. It therefore traces the direct female line, and everyone can test it.
It too reaches far back in time, but it carries much less detail. It is more useful for confirming or excluding a maternal-line hypothesis than for identifying a recent connection.
Autosomal DNA
Autosomal DNA is inherited from all of one’s ancestors rather than a single line. It is the test sold by the familiar consumer companies, and the best for finding relatives across the whole of a family.
Its limitation is reach. It is recombined and halved in every generation, so that after four or five generations there is too little of any one ancestor’s DNA left to trace a specific line. It is powerful for recent connections and population studies, less so for deep ancestry.
The Avotaynu DNA Project
The most substantial effort to map Jewish male lineages is the Avotaynu DNA Project, founded by Adam Brown.
Where an earlier generation of work had concentrated on Ashkenazi Jews, this project set out deliberately to test the non-Ashkenazi world: Sephardi, Mizrahi, Maghrebi, Romaniote and other communities, across some forty populations worldwide, from Bukhara to the New World. The project’s original announcement sets out its aims.
It was built with the geneticist Carlos Skorecki and a team including the Jewish-genetic-disease authority Harry Ostrer, the archaeologist Michael Waas, the geneticist Inês Nogueiro, and the biostatistician Wim Penninx.
It works chiefly from the Y chromosome, which suits its aim of tracing deep male-line ancestry. It operates under formal ethical approval, with a strict separation between a participant’s identity and their genetic data, so that the testing laboratory never knows whose sample it holds. The catalogue of Jewish Y-chromosome lineages the project has identified is maintained publicly by Wim Penninx at jewishdna.net.
A core Levantine population
The broad picture the project describes places the Jewish people within the frame of the Roman Empire. On Brown’s analysis that empire contained the great majority of the world’s Jews, and stretched from Babylon in the east to Iberia in the west. The organising question is where the Jews of that world are today, and the Y chromosome is the means of tracing them.
Further back, the work locates the origins of the Jewish people in the ancient Near East. Brown describes the Jewish people as arising out of the diverse background population of the Middle East around the collapse of the Late Bronze Age, rather than as a group set apart from it. Before that collapse, the ancestral lineages are largely indistinguishable from those of the other peoples of the region.
The genetic evidence, on this account, points to a core Levantine, Middle Eastern ancestry of great antiquity underlying the Jewish communities of the Mediterranean. It emerged from, and was never wholly separate from, the wider population of the ancient Near East.
From this common root the later communities diverged. The project’s reading of the lineage tree is that the Ashkenazi Jews are not a separate people but a subset of this older Mediterranean Jewish population who moved north and, cut off from the Mediterranean, developed their own language and customs. The tree preserves later moments of demographic expansion into Italy, France, Germany and, later still, Poland and Lithuania.
What Sephardic DNA testing has shown
For Sephardic family history specifically, the project’s testing has yielded several useful insights. All are reported here as findings of that work rather than claims of our own.
Diversity of descent. From the male line, the Jewish community descends not from a single founding father but from many hundreds of distinct lineages. The great majority of these are non-Ashkenazi. Before the medieval period most of the world’s Jews were not Ashkenazi.
The shape of the Sephardi dispersion. A single Iberian Jewish lineage is found scattered across the diaspora, appearing in the New World, Amsterdam and Aleppo, or across Greece, Italy, Curaçao, Portugal, Morocco, Salonica, the Balkans and Turkey. The Y chromosome can show that families separated by the expulsions, and now living continents apart, belong to one ancestral line.
Names and lineages do not match. The project finds that families coming out of Iberia often do not share a surname across a single genetic lineage. These families did not carry stable surnames before they adopted Christian names as New Christians in Portugal. The genetic line can be continuous where the name is not, which is an important caution for surname-based research. See our page on Sephardic surnames.
Judean is not the same as Iberian. The work distinguishes what is genuinely Judean in a family’s ancestry from what is simply Iberian or more broadly Middle Eastern. Because Jews lived in Iberia for some fifteen centuries, and because identity was fluid in the early Roman period, some lineages that are Iberian in deep origin later became part of the Jewish population. An ancestral line can therefore be Iberian in its distant roots and Jewish in its later history. The genetics records the ancestry but does not by itself say at what point in that long story a line became Jewish.
Why do Jewish DNA tests show thousands of cousins?
Where Y-DNA suits deep ancestry, most people who test do so with an autosomal test, through Ancestry, MyHeritage, 23andMe, or the Family Finder test at FamilyTreeDNA, in order to find cousins. For Sephardic and Ashkenazi researchers this raises a specific difficulty, addressed in Jarrett Ross’s talk to Sephardic World.
The difficulty is endogamy: centuries of marriage within a closed community. Because everyone in such a community shares small pieces of DNA with almost everyone else, a Jewish tester typically finds tens of thousands of apparent cousins. The autosomal test cannot tell which shared DNA corresponds to which cousin.
Ross draws the distinction between DNA shared because two people genuinely descend from a recent common ancestor, which is identical by descent, and DNA that merely appears shared, which is identical by chance. Endogamy inflates the second kind, producing a spike of false-positive matches. This is why raw match lists routinely make Sephardi relationships look far closer than they are.
The practical safeguard is the Shared Centimorgan Project, a chart built from large amounts of real-world data showing how much DNA relatives of each type actually share. Comparing a match against that reference is the check against over-reading it. In an endogamous community it is a reminder that a real relationship is usually more distant than the shared amount first suggests.
Used with this care, autosomal DNA is a genuine aid to Sephardic research. Used naively, it misleads.
Tools
These are the tools most often used by Sephardic researchers working with autosomal results.
- GEDmatch — compares results across the different testing companies, so that matches tested elsewhere can be found.
- DNA Painter — maps segments of shared DNA onto specific ancestral lines, and hosts the Shared Centimorgan tool.
- Dana Leeds — the Leeds Method, a way of sorting a match list into four grandparent groups.
Sephardic World lectures on DNA
- Sephardic DNA Project — Adam Brown
- DNA and Jewish Genealogy — Adam Brown
- Y-DNA and the Jews — Wim Penninx
- Finding Your DNA Cousins — Jarrett Ross
- Fun with Autosomal DNA: tackling genealogical uncertainty — Julian Land
- Using DNA to Track your Ancestors: a case study — Raquel Levy-Toledano
- Ancestral Origins and Genetic Diversity of Moroccan Jews — Raquel Levy-Toledano
- DNA Evidence of Jews in Portugal — Inês Pires Nogueiro
- A Moroccan Jewish Genealogical Journey — Raquel Levy-Toledano
- Do Ashkenazim Have Sephardic Ancestry? — Adam Brown, Randy Schoenberg, Alexander Beider, Ton Tielen and David Mendoza
- Data Mining the Deceased — Julia Creet
Professional help
DNA results are most useful when read alongside records rather than on their own. If you would like help interpreting a test in the context of a documented family, you can hire a Sephardic genealogist, or email us at [email protected].
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See also: Sephardic Surnames · Genealogical Standards · Crypto-Judaism and Bnei Anusim