The lessons of the Ashkenazim.

My grandparents were immigrants from Eastern Europe who owned a small necktie factory on the outskirts of Montreal. While visiting them one weekend, I found my grandfather on the factory floor, cutting shapes out of irregular stacks of cloth with a fabric saw. He explained that by carving up the remnants that were left over when the neckties had been cut out and stitching them together in places that didn't show, he could get a few extra ties out of each sheet of cloth. I asked him why he was doing this himself rather than leaving it to his employees. He shrugged, tapped his forehead, and said, "Goyishe kop," a term of condescension that literally means "gentile head."

He wasn't exactly serious, but he wasn't exactly not serious either. Jews have long had an ambivalent attitude toward their own intelligence, and toward their reputation for intelligence. There is an ethnic pride at the prevalence of Jews in occupations that reward brainpower. A droll e-mail called "New Words to Add to Your Jewish Vocabulary" includes "jewbiliation, N: pride in finding out that one's favorite celebrity is Jewish" and "meinstein, N: My son, the genius." Many Jews subscribe to a folk theory that attributes Jewish intelligence to what would have to be the weirdest example of sexual selection in the living world: that for generations in the shtetl, the brightest yeshiva boy was betrothed to the daughter of the richest man, thereby favoring the genes, if such genes there are, for Talmudic pilpul.

But pride has always been haunted by fear that public acknowledge of Jewish achievement could fuel the perception of "Jewish domination" of institutions. And any characterization of Jews in biological terms smacks of Nazi pseudoscience about "the Jewish race." A team of scientists from the University of Utah recently strode into this minefield with their article "Natural History of Ashkenazi Intelligence," which was published online in the Journal of Biosocial Science a year ago, and was soon publicized in The New York Times, The Economist, and on the cover of New York magazine.

The Utah researchers Gregory Cochran, Jason Hardy, and Henry Harpending (henceforth CH&H) proposed that Ashkenazi Jews have a genetic advantage in intelligence, and that the advantage arose from natural selection for success in middleman occupations (moneylending, selling, and estate management) during the first millennium of their existence in northern Europe, from about 800 C.E. to 1600 C.E. Since rapid selection of a single trait often brings along deleterious by-products, this evolutionary history also bequeathed the genetic diseases known to be common among Ashkenazim, such as Tay-Sachs and Gaucher's.

The CH&H study quickly became a target of harsh denunciation and morbid fascination. It raises two questions. How good is the evidence for this audacious hypothesis? And what, if any, are the political and moral implications?