Are modern Jews a ‘race’—the descendants of an ancient tribal people, as Biblical lore has it? Or do they trace their ancestry to Eurasia as Shlomo Sand, author of The Invention of the Jewish People, and Arthur Koestler in The Thirteenth Tribe, claim?

The latest DNA research offers extraordinary insights into the origins of the Jewish people and its impact on each of us. I addressed this controversy a few years ago in my book, Abraham’s Children: Race, Identity and the DNA of the Chosen People.

Now, Harry Ostrer, a medical geneticist and professor at Albert Einstein College of Medicine in New York, takes on the subject from the perspective of a scientist. His new book, Legacy: A Genetic History of the Jewish People, reaffirms the findings in Abraham’s Children, claiming that Jews are ‘different’, and the differences are not just skin deep.

“Who is a Jew?” has been a poignant question for Jews throughout history. It evokes a complex tapestry of Jewish identity made up of different strains of religious beliefs, cultural practices and blood ties to ancient Judea and modern Israel.

Jews exhibit, he writes, distinctive genetic signatures. Considering that the Nazis tried to exterminate Jews based on their supposed racial distinctiveness, such a conclusion might be a cause for concern. But Ostrer sees it as central to Jewish identity. Geneticists have long been aware that certain diseases,from breast cancer to Tay-Sachs, disproportionately affect Jews. Ostrer, who is also director of genetic and genomic testing at Montefiore Medical Center, goes further, maintaining that modern Jews are a mostly homogeneous group with all the scientific trappings of what we used to call a “race.”

Read Jon Entine's review of Legacy in the Jewish Daily Forward

Jon Entine, author of Abraham's Children: Race, Identity and the DNA of The Chosen People, is founder and director of the Genetic Literacy Project at George Mason University.