Modern Jews may traditionally trace their ancestry to the Holy Land, but a new genetic study finds otherwise. A detailed look at thousands of genomes finds that Ashkenazim—who make up roughly 80% of the world’s Jews, including 90% of those in America and half of those in Israel—ultimately came not from the Middle East, but from Western Europe, perhaps Italy.

Most mainstream historians regard Ashkenazim as the descendants of Jews who moved into central Europe from the Middle East sometime before the 12th century C.E. Ashekenazim, like most members of this religious, cultural, and ethnic group, traditionally trace their ancestry to the ancient Israelites. The Israelites, in turn, arose between 3000 and 4000 years ago in the Middle East, according to both Biblical sources and archaeological evidence. They dispersed after the Romans destroyed their Second Temple in Jerusalem in 70 C.E.

Recent genetic work has supported this traditional view. Two studies, one led by geneticist Harry Ostrer of the New York University School of Medicine, and the other by geneticist Doron Behar of the Rambam Health Care Campus in Haifa, Israel, traced the three main Diaspora groups—Ashkenazim, Sephardim from Spain and Portugal, and Oriental Jews from the Middle East—to people who all lived in the Middle East about 2000 years ago. The Ostrer study used DNA from the nucleus of the cell in its analyses, and the Behar study used both nuclear and mitochondrial DNA (mtDNA); the latter comes from tiny bodies in the living cell that provide it with energy. Many other researchers considered these results to be definitive at the time.

Yet there were lingering questions. Ostrer and Behar had samples from only a couple of hundred Jews, for example. And while the Behar group identified four major mtDNA “founder groups” for the Ashkenazim, all supposedly with roots in the Middle East, it was able to trace only about 40% of Ashkenazi ancestry overall.

So a different team of scientists, led by geneticist Martin Richards at the University of Huddersfield in the United Kingdom, embarked on a new search for the origins of these four founder groups. The team focused on mtDNA, which is often employed in genetic studies because it is easier to sequence and allows analysis of huge population samples. However, mtDNA is inherited through the mother and not the father, so it reveals the history of maternal lineages only.

Geneticists have identified certain mtDNA markers that define lineages in different parts of the world. Behar’s group had traced the Jewish founder groups to two mtDNA genetic lineages called haplogroup K and haplogroup N1b. The Jewish lineages were nested within these two larger groups, which include both Jews and non-Jews. So Richards and his colleagues first set out to understand the history of these broader lineages. They analyzed about 2500 complete and 28,000 partial mtDNA genomes of mostly non-Jews worldwide, plus 836 partial mtDNA genomes of Ashkenazi Jews, to see where the Ashkenazim fit into the overall history.

The result was very clear-cut, the authors say: As reported online today in Nature Communications, more than 80% of Ashkenazi mtDNAs had their origins thousands of years ago in Western Europe, during or before Biblical times—and in some cases even before farming came to that part of the continent some 7500 years ago. The closest matches were with mtDNAs from people who today live in and around Italy. The results imply that the Jews can trace their heritage to women who had lived in Europe at that time. Very few Ashkenazi mtDNAs could be traced to the Middle East.

The results not only conflict with the Ostrer and Behar results, but also with widespread assumptions about Jewish identity. Jews have traditionally considered that the mother determines the ethnic identity of her children. If being Jewish is defined as genetically descending from the Israelites through the maternal line, then many Ashkenazi Jews fail the test, according to this data.

Richards acknowledges that the work is likely to be controversial. “I’d anticipate some resistance to our conclusions in certain quarters,” he says. One way to reconcile his team’s findings with those of other researchers, he says, is to assume that the founders of the male Ashkenazi lineages were indeed originally from the Middle East, but that the maternal line arose in Europe much earlier. The European women then converted to Judaism after male Jews moved into the continent, establishing the Ashkenazi lineages that we see today. That suggestion fits with the contention of some historians that many women converted to Judaism across Mediterranean Europe during the so-called Hellenistic period between about 300 B.C.E. and 30 B.C.E.

“The data are very convincing,” says Antonio Torroni, a geneticist at the University of Pavia in Italy and a leading expert in the genetics of Europeans. He adds that recent studies of DNA from the cell nucleus have also shown “a very close similarity between Ashkenazi Jews and Italians.”

The new data also put the nail in the coffin of another, highly controversial, hypothesis about Jewish ancestry: that the Ashkenazim actually descend from the Khazars, a Turkic people in Western Asia’s Caucasus region whose rulers are known to have converted to Judaism in the 8th century C.E. That idea was promoted in a 2008 book by historian Shlomo Sand of Tel Aviv University in Israel. Ostrer and Behar found no such link, however, and Richards’s team, which sampled mtDNAs from Asia and the Caucasus specifically to test this idea, also found no evidence for it.

Behar remains unconvinced. He says it’s “clear that Ashkenazi maternal ancestry includes both [Middle Eastern] and European origins,” but he does not agree that the deepest roots of the Ashkenazi Jews can be found in prehistoric Europe. He says that he and his colleagues will be submitting their critique of the Richards study soon to a peer-reviewed scientific journal.

*Correction, 9 October, 12:40 p.m.: The photo that originally accompanied this story has been replaced, as the original photo was unrealistic.