Nber Working Paper Series Genetic Diversity and the Origins of Cultural Fragmentation

Despite the importance attributed to the effects of diversity on the stability and prosperity of nations, the origins of the uneven distribution of ethnic and cultural fragmentation across countries have been underexplored. 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 exploration of this uncharted territory may revolutionize the understanding of the effects of deeply-rooted factors on economic development and the composition of human capital across the globe. Quamrul Ashraf Williams College Department of Economics 24 Hopkins Hall Drive Williamstown, MA 01267 [email protected] Oded Galor Department of Economics Brown University Box B Providence, RI 02912 and NBER [email protected] Diversity has emerged as a fundamental force in the stability and prosperity of nations. The intensities of fractionalization and polarization across ethnic, linguistic, and religious groups have been associated with economic growth, the quality of governance, the provision of public goods, the prevalence of civil conflict, and endogenous nation formation.1 Nevertheless, the origins of the uneven distribution of ethnic and cultural fragmentation across countries have been largely neglected.2 An emerging body of evidence suggests that deeply-rooted factors, determined tens of thousands of years ago, have significantly affected the level of diversity and the course of comparative economic development from the dawn of human civilization to the contemporary era.3 In particular, Ashraf and Galor (2013) advance and empirically establish the hypothesis that, in the course of the prehistoric exodus of Homo sapiens out of Africa, migratory distance to various indigenous settlements across the globe adversely affected the level of genetic diversity, and thereby generated a persistent hump-shaped effect on development outcomes, reflecting the tradeoffbetween the beneficial and detrimental effects of diversity on productivity. Building upon the insight of the biogeographical roots of comparative development, this paper explores an underlying unity in the origins of the various forms of ethnic and cultural fragmentation in contemporary national populations. It advances the hypothesis that genetic diversity, determined predominantly during the migration of humans out of Africa tens of thousands of years ago, is a fundamental determinant of observed ethnic and cultural heterogeneity, as reflected by the number of ethnic groups and the levels of ethnolinguistic fractionalization and polarization within modern national boundaries. Following the “out of Africa”migration, the initial level of genetic diversity in indigenous settlements presumably facilitated the formation of distinct ethnic groups through a process of endogenous group selection, based on the tradeoff between the costs and benefits associated with heterogeneity and scale.4 While heterogeneity raised the likelihood of disarray and mistrust, reducing cooperation and thus adversely affecting group-specific productivity, complementarities across diverse productive traits and preferences stimulated productivity. Since in a given environment, diminishing marginal returns to diversity and homogeneity entail an optimal size for each group, higher initial genetic diversity would have positively contributed to the number of groups, and thus to the degree of fractionalization. Further, to the extent that higher initial diversity did not lead to an excessively large number of groups, it would have positively contributed to the degree of polarization as well.5 Consistent with the proposed hypothesis, this research establishes that genetic diversity is an underlying cause of a broad spectrum of existing manifestations of ethnic and cultural diversity. Exploiting migratory distance from East Africa as an exogenous source of cross-country variation in contemporary genetic diversity, the empirical analysis demonstrates that genetic diversity has signifiFor an overview, see Alesina and La Ferrara (2005). Recent exceptions are studies on the effects of geographical variability (Michalopoulos, 2012) and the duration of human settlement (Ahlerup and Olsson, 2012) on linguistic diversity. See Spolaore and Wacziarg (forthcoming) for a survey. Over time, as the forces of cultural drift augmented intergroup divergences in language, customs, and norms, thereby reinforcing the barriers to intergroup assimilation, distinct ethnic identities were formed. 5 If local geographical factors complemented a specific spectrum of productive traits and preferences, genetic diversity, coupled with spatial variability in geographical factors, may have facilitated the sorting of the regional population into spatially segregated communities, and thus the effect of genetic diversity on the degree of fractionalization or polarization could potentially be nonmonotonic.