New research shows U.S states that have banned close-kin marriage experienced faster economic development than those which did not. States with bans saw higher rates of secondary education completion as well as college attendance and graduation from the 1880s until the present This educational attainment was accompanied by a steady shift towards higher-paying occupations. The findings suggest that the bans were largely responsible for these social and economic changes, rather than genetics. Paper Referred to in Brief: here