The Role of Lactose Tolerance in Pre-Colonial Development

This paper establishes a link between natural selection since the Neolithic Revolution and economic conditions in the pre-colonial era. The ability to digest milk, or to be lactose tolerant, is conferred by a gene variant, which is unequally distributed across the Old World. Digesting milk conferred qualitative and quantitative advantages to early farmers's diets, which ultimately, led to differences in the carrying capacities of respective countries. It is shown through a number of specifications that country level variation in the frequency of the ability to consume milk is positively and significantly related to population densities in 1500 CE; specifically, a one standard deviation in- crease in the frequency of lactose tolerant individuals (24% points) is associated with roughly a 60% increase in pre-colonial population densities. This relationship remains while controlling for agricultural transition dates, other measures of genetic distance, and a wide array of environmental controls. Additionally, the basis for the relation- ship between dairying and population density is confirmed with the use of instrumental variables estimation.