Temperature, skin color, per capita income, and IQ: An international perspective

We correlated mean IQ of 129 countries with per capita income, skin color, and winter and summer temperatures, conceptualizing skin color as a multigenerational reflection of climate. The highest correlations were − 0.92 (rho = − 0.91) for skin color, − 0.76 (rho = − 0.76) for mean high winter temperature, − 0.66 (rho = − 0.68) for mean low winter temperature, and 0.63 (rho = 0.74) for real gross domestic product per capita. The correlations with population of country controlled for are almost identical. Our findings provide strong support for the observation of Lynn and of Rushton that persons in colder climates tend to have higher IQs. These findings could also be viewed as congruent with, although not providing unequivocal evidence for, the contention that higher intelligence evolves in colder climates. The finding of higher IQ in Eurasians than Africans could also be viewed as congruent with the position of Diamond (1997) that knowledge and resources are transmitted more readily on the Eurasian west–east axis.