How Genetics Paint A Picture Of The Jewish Past
From the time of the Babylonian Exile, Jews have been spread far and wide, carrying with us mementos of our ancient past in our blood, spit and the microscopic double helix of our DNA. Among the best tools the Chosen People have for finding a link to antiquity is bleeding-edge technology that analyzes our genes – and while that tech is new, it’s largely confirmed a familiar story of shared roots in the Middle East.
Through advancements in mapping the human genome and the study of traditionally diseases like Tay-Sachs, scientists and historians are closer than ever before to learning where the Jewish people originated, and where we ended up.
The science involved in genetic study of Jews has advanced immensely since its early days, when physical anthropologists Joseph Jacobs and Maurice Fishberg studied outward markers like stature, head size and pigmentation, said Harry Ostrer, the director of Genetic and Genomic Testing at Montefiore Medical Center and the author of “Legacy: A Genetic History of the Jewish People” (2012). Working in the late 19th and early 20th Century, when Fishberg published “The Jews: A Study of Race and Environment” (1911), his and Jacob’s primitive research – which had a troubling analogue in the measurements used by Nazi race science — was surpassed by a new effort that emerged, fittingly, in Mandatory Palestine.
After moving to Palestine in the 1930s, Chaim Sheba and other physician investigators observed that the Jewish communities flocking to the land from across the globe did not much resemble each other. Sheba and colleagues believed these differences ought to be studied. This work culminated in 1961, when Sheba and geneticist Elisabeth Goldschmidt held the Conference on Human Population Genetics in Jerusalem.
By the 1970s, studies using blood groups conducted by researchers like Arthur Mourant and Batsheva Bonne-Tamir advanced our understanding of Jewish common ancestry, as did studies in the 1990s focused on matrilineal mitochondrial DNA and patrilineal Y chromosomes. But it wasn’t until Jewish genomes, an individual’s entire genetic code, started being analyzed in the 2000s, following the breakthroughs of the Human Genome Project’s push to map all human genes, that this knowledge became less abstract.
Before genome-wide analyses, “There was a real lack of precision,” Ostrer told the Forward over the phone. “The Y chromosomal and mitochondrial studies supported the idea, for instance, for European Jews, that they had both Middle Eastern and European origins. But it just wasn’t with the degree of accuracy or precision that happened when the genome-wide studies were done.”
Ostrer’s initiative, the Jewish HapMap Project, is one of a number of studies propelled by advancements in genomic technology, which can now determine the order 20,000 genes (and 3 billion nucleotide base pairs) at one time in around one to two months. In recent years, these efforts have yielded insights into the inter-connectedness of the Jewish people.
“Part of why that research is so fascinating is it’s telling us about aspects of Jewish history that are not recorded in texts or reflected in archaeology,” said Steven Weitzman, the Ella Darivoff director of the Katz Center of Advanced Judaic Studies at the University of Pennsylvania and the author of “The Origin of the Jews: The Quest for Roots in a Rootless Age” (2017).
Weitzman, who collaborated with Stanford geneticists in his research, noted a few early landmark studies that seemed to confirm traditional narratives, that link Jewish Diasporic communities to common tribal ancestors in modern day Israel. One of the earliest, from 1997, was a Y-chromosomal analysis of Kohanim, which indicated a common male ancestor some 3,000 years ago.
”That doesn’t mean that ancestor is Aaron as Jewish tradition would indicate – and it’s since been challenged – but it was really striking that they could see reflected in the genetic code of these people that they did share a common male ancestor somewhere thousands of years ago.”
Since the completion of the Human Genome Project in 2003, more ambitious studies have been mounted, Weitzman said, including Doron Behar’s 2010 attempt to draw a genome-wide map of the Jewish people — a goal shared by Ostrer’s HapMap Project — by sampling DNA from 14 global communities. The study found that many of the communities differed genetically from their non-Jewish neighbors and had roots in the Middle East. While that tracks with conventional history, other research, such as a 2013 study by Martin B. Richards, concluded that the matrilineal line of Ashkenazic Jewish descent has its roots in native European women. Behar, who, with Karl Skorecki, had concluded years earlier that 40% of Ashkenazi Jews can trace their origins to four women of Middle Eastern extraction, disagreedwith this assessment.
“[Genetics] doesn’t necessarily corroborate the traditional Jewish understanding,” Weitzman said, “but it often does. And that’s why some people are a little skeptical. It’s been reaffirming a very conservative understanding of Jewish history.”
While the majority of scientists and historians support the view that Jews originated in the Middle East, there are vocal skeptics, notably Israeli geneticist Eran Elhaik and Israeli historian Shlomo Sand. Sand and Elhaik subscribe to the Khazar Hypothesis, popularized by author Arthur Koestler, which argues that Ashkenazi Jews are descended from a Turkic people called the Khazars, who converted. Ostrer and the broader scientific community have dismissed this theory, and Elhaik’s specific research, as “agenda-driven science.” Weitzman agrees that the theory presents a weak argument and has been used to discredit Jews and Zionism by distancing Ashkenazim from claims to a Middle Eastern homeland.
The preponderance of evidence, based on a number of studies, indicates a conventional view of Jewish diaspora, Ostrer claims. Jews appear to have migrated east along the Silk Road and across the Arabian Sea and westward into Europe and Northern Africa by way of the Greek and Roman empires. These migrants intermingled with locals — sometimes converting them to the faith — along the way. Despite this dispersion, Jews remained largely endogamous, marrying within our ethnic group, relative to native populations.
The same endogamy has historically resulted in genetic diseases, which, by medical necessity, have made Jewish genes among the most studied. While Ostrer cautions that some consumer-available genetic tests can be deceptive, appearing to indicate closer kinship between Jews who share deep ancestral lines, he maintains that the testing for potential disease carriers has improved tremendously with companies like JScreen, Invitae and Myriad.
Currently, those with Sephardic and Mizrahi backgrounds (roughly 10% of American Jews) don’t have the advantage of seeing that heritage listed in most popular genetic testing service results. But these populations are sufficiently studied by geneticists – and often analysis of these groups can lead to interesting places. Recently, disease mutations like BRCA 1 and 2 and hereditary ovarian and breast cancer typically found in Jews have been surfacing among Latino populations in the United States.
In a 2011 paper, Ostrer and his colleague Christopher Velez argued that these genetic predispositions were carried to the New World by Converso Jews in the late 15th century. New research from 2018 appeared to confirm this, finding that a wide swath of Latin Americans have ancestry from newly-converted Christians.
Overall, DNA testing and studies have enriched the Jewish historical record beyond potsherds and texts dating back to the Greek and Roman period. But while these science-based tools are often less ambiguous than previous historical documents, they have not been embraced by all historians. The reason, ironically enough, is recent history.
“There’s a lot of resistance to [genetic research] within the field of Jewish studies,” Weitzman said. “A lot of people remember or have in mind the role of race science in Nazism. So the idea that Jewish scholars would look in any way to genetics to understand Jewish identity or Jewish history and origins can make people concerned.”
PJ Grisar is the Forward’s culture fellow. He can be reached at [email protected]