As the Black Death swept through Europe in the mid-14th century, many Christians, observing that their Jewish neighbors tended to die at less alarming rates, decided that the Jews were to blame. This conclusion resulted in some of the Middle Ages’ severest outbreaks of anti-Semitic violence. Over the last 200 years, historians have variously pinned the difference in mortality to better hygiene (perhaps related to handwashing and other halakhic observances), more fastidious care for the sick, kashrut, and Passover cleaning. Declaring these explanations scientifically untenable, Kathryn Glatter and Paul Finkelman suggest a different one:

We believe that the answer lies in a recessive genetic mutation—familial Mediterranean fever (FMF), which is found mostly in people of Middle Eastern ancestry. In 14th-century Europe, the most prominent and visible group of such people would have been Jews. FMF causes recurrent fevers and painful inflammation of the abdomen, lungs, and joints. However, as a 2020 study at the National Human Genome Research Institute showed, it also makes its carriers resistant to the bubonic plague.

A recent analysis of 400 blood samples in Tel Aviv found FMF in 39 percent of Jews of Iraqi origin, 22 percent of Jews from North Africa, and 21 percent of Ashkenazi Jews. In another Israeli study, 14 percent of Jews of Turkish origin and 20 percent of Jews from Bukhara, Georgia, and Bulgaria carried the mutation. Altogether, it seems that 20 to 40 percent of Israeli Jews might carry the FMF mutation.

Since FMF is a recessive gene, its carriage rate has likely declined since the 14th century, meaning that many more Jews would have carried the FMF mutation at the time of the plague. If so, this would explain the contemporary impression that Jews survived the plague in disproportionate numbers compared with their Christian neighbors. The fact that thousands of them were then murdered, in part because of their congenital immunity, is one of the tragic ironies of history.

While it is commendable that administrators of several universities finally called upon police to crack down on violent and disruptive anti-Israel protests, the actions they have taken may be insufficient. At Columbia, demonstrators reestablished their encampment on the main quad after it had been cleared by the police, and the university seems reluctant to use force again. The school also decided to hold classes remotely until the end of the semester. Such moves, whatever their merits, do nothing to fix the factors that allowed campuses to become hotbeds of pro-Hamas activism in the first place. The editors of National Review examine how things go to this point:

Since the 10/7 massacre, Columbia’s Jewish students have been forced to endure routine calls for their execution. It shouldn’t have taken the slaughter, rape, and brutalization of Israeli Jews to expose chants like “Globalize the intifada” and “Death to the Zionist state” as calls for violence, but the university refused to intervene on behalf of its besieged students. When an Israeli student was beaten with a stick outside Columbia’s library, it occasioned little soul-searching from faculty. Indeed, it served only as the impetus to establish an “Anti-Semitism Task Force,” which subsequently expressed “serious concerns” about the university’s commitment to enforcing its codes of conduct against anti-Semitic violators.

But little was done. Indeed, as late as last month the school served as host to speakers who praised the 10/7 attacks and even “hijacking airplanes” as “important tactics that the Palestinian resistance have engaged in.”

The school’s lackadaisical approach created a permission structure to menace and harass Jewish students, and that’s what happened. . . . Now is the time finally to do something about this kind of harassment and associated acts of trespass and disorder. Yale did the right thing when police cleared out an encampment [on Monday]. But Columbia remains a daily reminder of what happens when freaks and haters are allowed to impose their will on campus.