The origin of the uneven distribution of ethnic and cultural fragmentation across countries has been underexplored, despite the importance attributed to the effects of diversity on the stability and prosperity of nations. Building on the role of deeply-rooted biogeographical forces in comparative development, this research empirically demonstrates that genetic diversity, predominantly determined during the prehistoric “out of Africa” migration of humans, is an underlying cause of various existing manifestations of ethnolinguistic heterogeneity. Further research may revolutionize our understanding of how economic development and the composition of human capital across the globe are affected by these deeply-rooted factors.