Global behavioral variation: A test of differential-K

Despite Rushton’s path-breaking work into evolutionary forces affecting life history traits, not many attempts at operationalizing the differential-K spectrum at the level of countries or racial groups have been made so far. We report the construction of a “national K” factor from country-level behavioral variables. This K factor is closely related to country-level intelligence (“g”), operationalized by a composite score of IQ and scholastic achievement. We further demonstrate relationships of both g and K with measures of current environment and hypothesized evolutionary antecedents. Whereas K is predicted most powerfully by intelligence, log-transformed GDP (lgGDP) and skin reflectance, g is predicted by skin reflectance, lgGDP, cranial capacity, and a measure of evolutionary novelty.

► We construct a national-K factor using six life history relevant variables. ► This construct is investigated along with a national g measure. ► Evolutionary variables more strongly predict g. ► Developmental variables more strongly predict K. ► Evolutionary history accounts for 80% of the variance in K and 85% the variance in g. ► Population stratification and co-selection might account for the observed relations.