Scientists: Gene may affect IQ in males

DALLAS — Scientists in North Carolina say they have identified a gene that affects IQ, a finding that, if confirmed, would be a significant step toward understanding the genetic basis for intelligence.

The new research also could have ethical implications because the effect of the gene appears dramatic: The scientists say males who inherit a particular version of the gene have, on average, an IQ 20 points lower than males who don't.

"I have to admit, the ramifications of it are great," said Randy Jirtle, the Duke University biologist who led the new research, noting that current genetic-testing techniques can easily determine which males have the gene version and which do not.

However, he stressed that the IQ results in his research were based on a group average; individual males carrying the gene version had a wide range of IQ scores. While females also can carry the gene variation, it does not appear to affect their IQ, he said.

Jirtle reported the new findings last month at a conference in Durham, N.C.

As early as the 1920s, research suggested that genetics play a key role in determining a person's mental capabilities.

But so far, connections between IQ and specific genes have been just correlations, with little supporting evidence. The new research, Jirtle and other experts said, will need to be replicated before it is considered definitive.

Jirtle's research focuses on a gene identified by the abbreviation IGF2R, for type 2 insulinlike growth factor receptor. The gene governs the production of a protein that affects cell growth. All people carry the gene, but some have a version with a slightly different code, or variation, Jirtle said. This gene variation, he and his colleagues found, correlates with a lower IQ.

The researchers studied about 300 children with an average age of 10. The children, all Caucasian, came from six counties in the Cleveland area. As a group, males — but not females — who had the variant gene had IQ scores about 20 points lower than males who didn't.

Jirtle cautioned that inheriting the different version of the gene did not guarantee a lower IQ. Although as a group average IQ scores were lower, there were males who had the variant gene and a higher IQ. And males with the more common form of the gene can also can have a lower IQ.

The new research has not been published in a journal, so it is not widely known in the scientific community. And many researchers question the usefulness of IQ as a measure of mental ability, saying it's a broad measurement.

"I think they are probably looking at something much smaller than IQ, like reaction time or working memory," said Elena Grigorenko, a geneticist and psychologist at Yale University School of Medicine in New Haven.

The new research is likely to spark interest among parents and those considering having children, said Arthur Caplan, a bioethicist at the University of Pennsylvania in Philadelphia. He said he could imagine people wanting to test newborns — or even embryos created through in vitro fertilization — for the gene.

"Parents are very concerned about intelligence in their kids," Caplan said. "I could imagine people saying, 'We want to sort out our embryos to get the smartest kids possible.' "

Currently, some genetic testing is done with in vitro fertilization or in higher-risk pregnancies, but it's done to avoid genetic disease. Using genetic testing to assess positive traits, such as higher IQ, takes ethical discussions to a new level, he said.

If the new results connecting IQ with the IGF2R gene are confirmed, Caplan said it will be important to remember that IQ tests measure only certain types of mental abilities, including analytical thinking and mathematical ability. The tests don't capture emotional intelligence, social skills, motivation or artistic and musical talent.

It's still unclear why the gene has an effect on IQ only in males, Jirtle said. "There must be an advantage. It was selected for something, but I can't believe it was to make males dumber."