A study by a University of Utah anthropologist and colleagues, linking intelligence of Ashkenazi Jews with genetic changes, is drawing attention worldwide. The latest example is the Oct. 24 edition of New York Magazine, where an article about the research is the cover story.

The article is labeled "The Jewish Brain."

"Are Jews smarter?" the cover asks. "Why the controversial new study of Jewish intelligence has everybody plotzing." (The last word is Yiddish for bursting with emotion.)

Authors of the study, "Natural History of Ashkenazi Intelligence," are Gregory Cochran, a freelance physicist who lives in Albuquerque and is the lead author; Henry Harpending, distinguished professor of anthropology at the U., and Jason Hardy, who was an undergraduate at the U. when the research was carried out.

Harpending noted that the article has been accepted by the Journal of Biosocial Science and has been published online. (A copy is posted at http://harpend.dsl.xmission.com/Documents/AshkenaziIQ.jbiosocsci.pdf) It has generated some commentary, including a Scripps Howard News Service column published in this newspaper in June.

According to the online encyclopedia Wikipedia, which posts a link to the paper, the Ashkenazi Jews, or Ashenazim, lived in southern Europe, but better opportunities induced them to migrate to the country along the Rhine River, Germany, during the Dark Ages. According to Wikipedia, the Ashkenazim now make up about 80 percent of the world's Jews.

In the Dark Ages, Christians were forbidden to practice "usury," or lending money for interest. The Ashkenazim stepped into the gap, focusing on financing professions and providing the loans that society needed.

The paper cites an earlier study showing that around the year 1270, of 228 adult male Jews listed in Roussillon, France, almost 80 percent were moneylenders.

"The finding is that if a population is suddenly subjected to very strong selection in a new direction . . . the first thing that happens is there show up a lot of broken genes that, in combination with the regular ones, are favored in the new regime," Harpending said.

In this case, genes favoring development of skills in math and other intellectual pursuit are favored. The non-Jewish farmers and knights who lived nearby might not need the same sort of intelligence, so there was not this evolutionary pressure for it to thrive, according to the theory.

Presumably, Jews who did best at these pursuits became wealthy and had larger families, passing along their genes.

"Ashkenazi Jews have the highest IQ for any ethnic group for which there are reliable data," the study says.

"During the 20th century, they made up about 3 percent of the U.S. population but won 27 percent of the U.S. Nobel science prizes and 25 percent of the ACM Turing awards. They account for more than half of world chess champions."

Harpending said the study should have made more distinctions concerning Sephardi Jews, but said that wouldn't have made a major difference in the figures.

Greater brain power came with a biological price. The idea Harpending and colleagues want to explore is that certain genetic diseases, called sphingolipid mutations, boost intelligence. They seem to increase axonal growth and branching in the brain, which could improve brain power.

The downside is that the mutations also cause a number of debilitating, and sometimes fatal, diseases such as Tay-Sachs, Gaucher and Niemann-Pick diseases.

"We do have strong but indirect evidence that one of these, Gaucher disease, does indeed increase IQ," says the paper. Ari Zimran, who heads the Gaucher Clinic in Jerusalem, furnished the authors a list of the occupation of 302 of the patients, essentially all the Gaucher patients in Israel.

"Of the 255 patients who are not retired and not students, 81 are in occupations that ordinarily average IQ's greater than 120," it says. An IQ of 100 is considered normal.

"There are 13 academics, 23 engineers, 14 scientists, and 31 in other high IQ occupations like accountants, physicians or lawyers."

The genetic disorders are of the type that if one parent has the gene and the other does not, the child is healthy; if both have the broken gene, there could be illness. However, in cases like the form of Gaucher disease that Jewish people sometimes have, the ailment can be mild. "Lots of people go through their lives, they never know they're sick," Harpending said.

In cattle breeding, he said, certain genetic changes are encouraged because they produce cattle with a lot of muscle mass, when the animal has one of the defective genes. With two copies, the calf either doesn't get born or does not live long, he said.

The authors wondered if the inherited diseases were present "because there was strong selection for intelligence?" Perhaps the ailments "boosted intelligence in the heterozygote (one defective gene) state."

But couldn't the genetic diseases that some Jewish people have be coincidence, based on their developing in a small, isolated population? Harpending doesn't think so.

DNA studies would have uncovered a genetic bottleneck if there had been one, but they did not.

Still, he emphasized that this is a hypothesis. "We wrote the paper in the hope that people would collect some more data on it," he said.

E-mail: bau@desnews.com