Weak widespread (polygenic) selection is a mechanism that acts on multiple SNPs simultaneously. The aim of this paper is to suggest a methodology to detect signals of polygenic selection using educational attainment as an example. Educational attainment is a polygenic phenotype, influenced by many genetic variants with small effects. Frequencies of 10 SNPs found to be associated with educational attainment in a recent genome-wide association study were obtained from HapMap, 1000 Genomes and ALFRED. Factor analysis showed that they are strongly statistically associated at the population level, and the resulting factor score was highly related to average population IQ (r=0.90). Moreover, allele frequencies were positively correlated with aggregate measures of educational attainment in the population, average IQ, and with two intelligence increasing alleles that had been identified in different studies. This paper provides a simple method for detecting signals of polygenic selection on genes with overlapping phenotypes but located on different chromosomes. The method is therefore different from traditional estimations of linkage disequilibrium. This method can also be used as a tool in gene discovery, potentially decreasing the number of SNPs that are included in a genome-wide association study, reducing the multiple-testing problem and required sample sizes and consequently, financial costs.
Dual-inheritance theory posits that the genotype has an impact on the evolution of human behavior and that cultural traits can be constrained by genetic imperatives. A large body of studies provides evidence that the functional catechol-O-methyltransferase (COMT) Val158Met polymorphism is associated with executive function, working memory (WM), and intelligence. A survey of the population genetics database provides evidence that COMT gene frequencies vary across populations. The aim of the present study was to test the hypothesis that the COMT gene has an impact on cultural evolution, specifically on the adoption of an agricultural vs. a hunter-gatherer lifestyle. Statistically significant differences in COMT allele frequencies between hunter-gatherer and agricultural societies were found. Ethnic groups whose economy is based on farming have higher frequencies of the Met allele (symbol: A), whereas societies based on a hunter-gatherer economy have very low frequencies of the Met allele and a disproportionate predominance of the Val allele. Moreover, the frequency of the Met allele was positively correlated to the populations’ IQ (r = 0.57). The FNBP1L gene (rs236330) is associated with childhood and adult intelligence and it varies in frequency across populations. Frequency of rs236330 was also significantly correlated with the populations’ IQ (r = 0.81). COMT and FNBP1L had fairly similar geographical distributions (r = 0.44) although the result did not reach statistical significance. The results suggest that the genotype of a population influences its cultural development in fairly specific and predictable ways. Met allele frequency was positively correlated with latitude (r = 0.56), suggesting selective pressure due to climate.