The role of height in the sex difference in intelligence.

Recent studies conclude that men on average have higher intelligence than women by 3-5 IQ points. However, the ultimate evolutionary question of why men should have evolved to have higher intelligence than women remains. We suggest that men may have slightly higher intelligence than women through 4 mechanisms: (1) assortative mating of intelligent men and beautiful women, (2) assortative mating of tall men and beautiful women, (3) an extrinsic correlation between height and intelligence produced by Mechanisms 1 and 2, and (4) a higher-than-expected offspring sex ratio (more sons) among tall (and hence intelligent) parents. Consistent with our suggestion, we show that men may have higher IQs than women because they are taller, and once we control for height women have slightly higher IQs than men.The correlation between height and IQ and the female advantage in intelligence persist even after we control for health as a measure of genetic quality, as well as physical attractiveness, age, race, education, and earnings. Height is also strongly associated with intelligence within each sex.