While, at this point in time, it is abundantly clear that genes play some role in the development of human intelligence, which of them are involved – and to what degree – remains to be discovered.
As a contribution to this line of inquiry, a team of researchers from around the world has looked at 13 studies conducted in the past and containing comprehensive genetic profiles and IQ test results for a total of 78,000 subjects of European descent.
In a study published on Monday in the journal Nature Genetics, the researchers had identified 52 individual gene variants linked to intelligence, 40 of which had not been accounted for in the past.
According to the authors, these genetic factors may explain up to 20 percent of variance in human ‘smarts’ as per standardised intelligence tests.
“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 main author on the study.
While the finding held up even after correlating IQ with the newly identified gene variants in a vast database that was not used in the study itself, the amount of raw data and computing power needed to scan millions of genomes to find all of the relevant genes is still a ways off.
“For intelligence, there are thousands of genes,” said Posthuma. “We have detected the 52 most important ones, but there will be a lot more.”
Current estimates hold that around half of measured intelligence is genetically determined, although developing a simple IQ test based on an exhaustive list of bits of DNA might not be viable – at least in the foreseeable future.
“We are looking at all these genetic effects in isolation,” said Posthuma. “Maybe it’s a certain pattern of genetic variants that makes you more intelligent.”
Interestingly, people with the ‘smart genes’ were more likely to spend more years in school, be taller and have a larger head in infancy, and be autistic; and less likely to smoke and develop Alzheimer’s disease and depression.
Conversely, those without the intelligence-boosting genes were more likely to have schizophrenia and suffer from obesity.