A new paper published in Molecular Psychiatry claims to elucidate the role genes play in intelligence, says the Washington Post's Rob Stein. The GWAS study, conducted by the University of Edinburgh's Ian Deary and his colleagues, shows that while genes do play an important role, environment is equally important. The team analyzed DNA from 3,511 unrelated adults to study the impact of more than 540,000 SNPs on a person's intelligence. "Previous studies involving twins and adopted children have indicated that genes do play an important role in intelligence, perhaps accounting for about half the variation among individuals," Stein says. "But the relative contributions of genetics and environment remain controversial, and it has been unclear how much of a factor genes are. And scientists have been frustrated in their attempts to identify specific genes that may be involved in IQ." This study calculated that about 40 percent to 50 percent of individual differences in intelligence are due to genetics, but also found that the differences are influenced by many different genes, each playing a small role, and not one or two genes making all the difference, Stein adds.