This interesting new paper suggests that cognitive changes are triggered by changes in the economic significance of education. In other words, as society places greater cognitive demands, individuals must become smarter to deal with these demands, and they become smarter via education, i.e., by spending more time training their brains to perform in the more demanding environment. This theory sounds plausible. Better living conditions and better education probably account for the observed worldwide differences in intelligence.
Intelligence (Early View)
Educational and ecological correlates of IQ: A cross-national investigation
The new paradigm of evolutionary social science suggests that humans adjust rapidly to changing economic conditions, including cognitive changes in response to the economic significance of education. This research tested the predictions that cross-national differences in IQ scores would be positively correlated with education and negatively correlated with an agricultural way of life. Regression analysis found that much of the variance in IQ scores of 81 countries (derived from [Lynn, R., & Vanhanen, T. (2002). IQ and the wealth of nations. Westport, CT: Praeger]) was explained by enrollment in secondary education, illiteracy rates, and by the proportion of agricultural workers. Cross-national IQ scores were also related to low birth weights. These effects remained with national wealth, infant mortality, and geographic continent controlled (exception secondary education) and were largely due to variation within continents. Cross-national differences in IQ scores thus suggest that increasing cognitive demands in developed countries promote an adaptive increase in cognitive ability.