Migration and categorical inequality

Migration is a fundamental feature of the human condition. Human beings emerged in Africa some 150,000 years ago, and within a very short time (geologically speaking) they spread out to occupy the entire globe. Th ey reached Asia approximately 100,000 years ago, Australia 50,000 years ago, the Americas 15,000 years ago, and the outer islands of Polynesia 2,000 years ago (Goldin, Cameron and Balarajan 2011). Th e progressive expansion of the human population outward from Africa was accomplished through geographic mobility, showing that migration has always been critical for human adaptation (Coale 1974; McNeil 1979). In response to changing material conditions people historically have moved with the goal of improving their circumstances (Cavalli-Sforza and Cavalli-Sforza 1995). Homo sapiens is the only species that has been able to inhabit virtually every ecological niche on the planet, a feat accomplished through the uniquely human strategy of combining migration with cultural adaptation (Massey 2005).