Prehistoric Shuttle Dispersals in a Malthusian Economy

Early humans undertook multiple waves of migration out of Africa and back to the continent. We explore prehistoric human migration in a two-region Malthusian growth model. Whether migration occurs depends on the migration cost, relative population size, relative land supply, and relative hunting-gathering productivity between regions. Suppose one region is initially uninhabited. Then, a lower migration cost leads to migration and a larger human population. Back migration occurs when hunting-gathering productivity and supply of natural resources in the foreign region decrease relative to the home region, which provides an economic rationale for the multi-directional “shuttle dispersal model” of prehistoric human migration out of and back to Africa.