'Smart genes' account for 20% of intelligence: study

PanARMENIAN.Net - Scientists on Monday, May 22 announced the discovery of 52 genes linked to human intelligence, 40 of which have been identified as such for the first time, AFP reveals.

The findings also turned up a surprising connection between intelligence and autism that could one day help shed light on the condition's origins.

Taken together, the new batch of "smart genes" accounted for 20 percent of the discrepencies in IQ test results among tens of thousands of people examined, the researchers reported in the journal Nature Genetics.

"For the first time, we were able to detect a substantial amount of genetic effects in IQ," said Danielle Posthuma, a researcher at the Center for Neurogenomics and Cognitive Research in Amsterdam, and the main architect of the study.

"Our findings provide insight into the biological underpinnings of intelligence," she told AFP.

Most of the newly discovered gene variants linked to elevated IQ play a role in regulating cell development in the brain, especially neuron differentiation and the formation of neural information gateways called synapses.

An international team of 30 scientists combed through 13 earlier studies in which detailed genetic profiles and intelligence evaluations -- based on IQ tests -- had been compiled for 78,000 people, all of European descent.

Increasingly powerful computers have made it possible to scan and compare hundreds of thousands of genomes, matching tiny variations in DNA with diseases, body types or, in this case, native smarts.

The human genome has some 25,000 genes composed of more than three billion pairing of building-block molecules.

Many of the genetic variations linked with high IQ also correlated with other attributes: more years spent in school, bigger head size in infancy, tallness, and even success in kicking the tobacco habit.

One of the strongest -- and most surprising -- links was with autism, noted Posthuma.

"Gene variants associated with high IQ are also associated with higher risk of autism spectrum disorder," she said in an interview.

One gene in particular -- SHANK3 -- "is a very good candidate for explaining that," she added.

Conversely, the absence of certain high-IQ genes was more common in people suffering from schizophrenia or obesity.