The impetus for our study was the contention of both Lynn Race differences in intelligence: A global perspective. Mankind Quarterly, 31, 255-296] and Rushton (Rushton . Race, evolution and behavior: A life history perspective. New Brunswick, NJ: Transaction; Rushton, J. P. (1997). Race, intelligence, and the brain: The errors and omissions of the revised edition of S.J. Gould's the mismeasurement of man. Personality and Individual Differences, 23, 169-180;Rushton, J. P. (2000). Race, evolution, and behavior. A life history perspective (3rd edition). Port Huron: Charles Darwin Research Institute] that persons in colder climates tend to have higher IQs than persons in warmer climates. 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 À 0.92 (rho = À 0.91) for skin color, À0.76 (rho = À0.76) for mean high winter temperature, À0.66 (rho = À 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. D 2005 Elsevier Inc. All rights reserved.Both Rushton ( , 1997Rushton ( , 2000 and have pointed out that ethnic groups in colder climates score higher on intelligence tests than ethnic groups in warmer climates. They contend that greater intelligence is needed to adapt to a colder climate so that, over many generations, the more intelligent members of a population are more likely to survive and reproduce. Their temperature and IQ analyses have been descriptive rather than quantitative, however. In the present quantitative study, we predicted a negative correlation between IQ and temperature. We hypothesized that correlations would be higher for mean winter temperatures (January in the Northern Hemisphere and July in the Southern Hemisphere) than for mean summer temperatures. Skin color was conceptualized as a variable closely related to temperature. It is viewed by the present authors as a multigenerational reflection of the climates one's ancestors have lived in for thousands of years. Another reason to predict correlations of IQ with temperature and skin color is the product-moment correlation reported by Beals, Smith, and Dodd (1984) from every continent and representing 122 ethnically distinguishable populations. Jensen (1998) reasoned that natural selection would favor a smaller head with a less spherical shape...