Jewish legacy inscribed on genes?

They have been sneered at by colleagues and excoriated on Internet forums. They have been welcomed to speak at a synagogue and a Jewish medical society. They were asked to write a book. The 10,000 Year Explosion was published in February.
Cochran,55,and Harpending,65,say there’s no question that,as a whole,Ashkenazi Jews—those of European descent—have an abundance of brain power. Psychologists and educational researchers have pegged their average IQ at between 107.5 and 115. When a group’s average IQ is 100,the percentage of people above 140 is 0.4 per cent; when the average is 110,the genius rate is 2.3 per cent. “People are perfectly willing to admit that some people are taller or some people are shorter,” Cochran said. “But no one wants to say,‘This group is smarter.’ ”

Cochran,who has a doctorate in physics,developed satellite imaging systems and other optics hardware for Hughes Aircraft in El Segundo,California,in the 1980s. When the Cold War ended and defense budgets shrank,he moved his family to Albuquerque and became an optics consultant while indulging his amateur interest in biology. He worked for a while with evolutionary biologist Paul Ewald on theories that common disorders such as heart disease and Alzheimer’s are caused by germs. The pair courted controversy by postulating that some unidentified pathogen prompts a hormonal imbalance that makes babies more likely to become gay.

Cochran became intrigued by the deadly Ashkenazi diseases: Tay-Sachs,a neurological disorder that debilitates children before killing them,usually by age 4; Canavan disease,which turns the brain into spongy tissue and typically claims its victims before they can start kindergarten; Niemann-Pick Type A,in which babies accumulate dangerous amounts of fats in various organs and suffer profound brain damage and death before age 2.

He was struck by the fact that so many Jewish diseases involved problems with processing the same fat molecules,called sphingolipids,that transmit nerve signals. This seemed an unlikely coincidence. Genetically isolated groups often have higher rates of certain diseases. But of the more than 20,000 human genes,only 108 are known to be involved in sphingolipid metabolism. The odds of Ashkenazi Jews having four sphingolipid storage disorders by random chance are less than 1 in 100,000,he calculated.
He talked it over with Harpending,an expert in human population genetics. They came to believe this was an example of heterozygote advantage—where having two copies of a mutated gene can mean disaster but one copy is helpful.

Jews first came to Europe in the eighth and ninth centuries. They worked as traders before taking financial jobs made available by Christians who were religiously forbidden from charging interest. By 1100,local registries listed most Ashkenazi as lenders. That set the stage for natural selection to do its work,Cochran and Harpending theorise. According to the theory,the smartest individuals made the most money,and the wealthiest families had the most surviving children. The genes of the most intelligent Jews spread most,slowly raising the average IQ of the group. Over 40 generations—roughly 1,000 years—an increase of just three-tenths of an IQ point per generation would add up to a cumulative advantage of 12 IQ points,Cochran and Harpending conclude.
_Karen Kaplan,LATWP