A landmark article went online a few days ago in the journal Molecular Psychiatry. The study was prepared by a team of 32 researchers headed by the University of Edinburgh’s Gail Davies and entitled “Genome-wide association studies establish that human intelligence is highly heritable and polygenic.” The study’s methods do not lend themselves to easy explanation unless you’re at home with SNPs (single nucleotide polymorphisms) and inverse variance weighted models used to capture “the variance in the trait that is due to linkage disequilibrium between genotyped SNPs and unknown causal variants.” But the bottom line of the article is reasonably simple. Using nothing but genetic information, the team of researchers was able to establish that the narrow heritability of crystallized intelligence (the kind that can be more easily affected by education) is at least 40 percent. The narrow heritability of fluid intelligence (the kind that involves pure problem-solving ability, independently of acquired knowledge) is at least 51 percent. Note the at least. The study’s authors explicitly state that these estimates are lower bounds.
Shelves of books and articles denying or minimizing the heritability of IQ have suddenly become obsolete. Those who continue to claim that IQ tests don’t measure anything real inside the brain also have their work cut out for them.