Statistical associations between genetic polymorphisms modulating executive function and intelligence suggest recent selective pressure on cognitive abilities

Abstract

The hypothesis of the present paper is that cognitive abilities have undergone recent positive selection in human populations. Executive function is a multifactorial, polygenic phenotype, influenced by many genetic variants with small effects. Two genes (COMT Val158Met and CHRNA4) located on different chromosomes play an important role in modulating executive function via the dopamine and the cholinergic system. Frequencies of two SNPs known to have an association with similar facets of executive function (i.e. stable cognition and sustained attention) were obtained from 1000 Genomes. As a comparison, frequencies of three SNPs thought to influence IQ were obtained from 1000 genomes. Frequencies of the two alleles that are thought to increase sustained attention within populations had a significant positive correlation across populations. The same pattern was observed for intelligence SNPs, which were also strongly correlated with population IQs. However, intelligence and executive function alleles were only weakly correlated across populations. This finding supports the hypothesis that recent natural selection acted on executive function via different genes located on different chromosomes and modulating different neurotransmitter systems. Evidence for recent selection on intelligence was also found, and this overlapped to a limited extent with selective pressure on executive function