The author provides a detailed investigation of the facts surrounding human mental ability, its measurement, inheritability, possible neurobiological underpinnings, and its role as a currency in human mate choice. He links human mental ability with educational attainment, occupational attainment, occupational prestige, and earned income. The ethical and policy implications are profound for both liberal democratic and libertarian social thought.Class mobility is significantly mediated by human intelligence, and intelligence itself is significantly heritable. Liberal democratic and libertarian conservative social policies require substantial revision in light of these findings. New forms of socioenvironmental and genomic intervention recommend themselves.The author provides a detailed investigation of the facts surrounding human mental ability, its measurement, inheritability, possible neurobiological underpinnings, and its role as a currency in human mate choice. He links human mental ability with educational attainment, occupational attainment, occupational prestige, and earned income. The ethical and policy implications are profound for both liberal democratic and libertarian social thought.