Bite and Divide: Malaria and Ethnolinguistic Diversity

We investigate the epidemiological origins of ethnic diversity and its persistence. First, we conceptualize the role of malaria for the incentives to voluntary isolation in a Malthusian environment. The theory predicts that interactions in multiple geographically clustered groups with high sexual endogamy allowed limiting disease prevalence and increasing group fitness in pre-modern populations exposed to malaria. Second, using disaggregate level data, we document the hitherto unexplored and robust role of malaria for pre-colonial, historical and contemporaneous ethnic diversity in Africa. Third, falsification tests based on malaria epidemiology and history further allow us to validate the specific predictions of the model. No effect can be detected for other placebo vector-borne diseases. Malaria is a main driver of pre-colonial ethnic diversity in Africa but not in the Americas, where the pathogen was absent before European colonization. Fourth, the effect of ancestral malaria on endogamic cultures is the main predicted channel for the persistence of African ethnicities. Exploiting within village variation across 18 African countries, we find that ancestral malaria, but not malaria today, still affects the differential persistence of ethnicities through its legacy of active endogamic cultures.