Historical migration and contemporary health

Abstract

We argue that migration during the last 500 years induced differences in contemporary health outcomes. The theory behind our analysis builds on three physiological facts. First, vitamin D deficiency is directly associated with higher risk of all-cause mortality. Second, the ability of humans to synthesize vitamin D from sunlight (UV-R) declines with skin pigmentation. Third, skin pigmentation is the result of an evolutionary compromise between higher risk of vitamin D deficiency and lower risk of skin cancer. When individuals from high UV-R regions migrate to low UV-R regions, the risk of vitamin D deficiency rises markedly. We develop a measure that allows us to empirically explore the aggregate health consequences of such migration in a long historical perspective. We find that the potential risk of vitamin D deficiency induced by migration during the last half millennium is a robust predictor of present-day aggregate health indicators.