The present study examines predictions from Rushton’s differential K theory that diverse traits covary with intelligence, reproductive strategies, speed of maturation, parental care, and longevity. The predictions are tested by inter-correlating 129 cross-national differences in IQ, birth rate, infant mortality, HIV/AIDS, and life expectancy. A K super-factor accounted for 75% of the variance. Moreover, the correlations were significantly higher with skin color, a biological variable, than they were with gross domestic product (GDP), a culturally influenced variable. The median of the 21 inter-correlations among the seven variables was 0.68.