This research explores the persistent effect of the prehistoric exodus of Homo sapiens from Africa on the composition of human traits within human populations and, thus, on comparative economic development across societies from the dawn of civilization to the contemporary era.

This research has advanced the hypothesis and empirically established that migratory distances from the cradle of mankind in East Africa to the indigenous settlements of the ancestral populations of nations or ethnic groups, and its negative impact on their levels of diversity generated a persistent hump-shaped influence on development outcomes, reflecting the fundamental trade-off between the beneficial and detrimental effects of diversity on productivity at the societal level.

Although diversity diminishes interpersonal trust, cooperation, and economic coordination, adversely affecting the productivity of society, complementarity and cross fertilization across diverse productive traits stimulates innovations and gains from specialization, thus contributing to society's economic performance. In the presence of diminishing marginal returns to diversity and homogeneity, the aggregate productivity of ethnic groups, countries, or regions that are characterized by intermediate levels of diversity is therefore expected to be higher than that associated with excessively homogenous or heterogeneous societies.

Consistent with the fundamental building blocks of this hypothesis, empirical evidence indicates that interpersonal population diversity has:

  • An adverse effect on social cohesion, as reflected by greater ethnolinguistic fractionalization, lower trust,  and great prevalence of ethnic conflicts. 

  • A beneficial effect on innovative activity,  occupational heterogeneity, and gains from specialization, and cross-fertilization in classrooms and decision making of board of directors.

Moreover, population diversity has shaped the nature of both precolonial and contemporary political institutions. In particular, although diversity triggered the development of institutions for mitigating the adverse influence of diversity on social cohesion, the contribution of diversity to economic inequality and class stratification ultimately led to the formation and persistence of extractive and autocratic institutions.







Arbatlı, C. E., Ashraf, Q. H., Galor, O., & Klemp, M. (2020). Diversity and conflict. Econometrica, 88(2), 727-797.

This research advances the hypothesis and establishes empirically that interpersonal population diversity, rather than fractionalization or polarization across ethnic groups, has been pivotal to the emergence, prevalence, recurrence, and severity of intrasocietal conflicts. Exploiting an exogenous source of variations in population diversity across nations and ethnic groups, as determined predominantly during the exodus of humans from Africa tens of thousands of years ago, the study demonstrates that population diversity, and its impact on the degree of diversity within ethnic groups, has contributed significantly to the risk and intensity of historical and contemporary civil conflicts. The findings arguably reflect the contribution of population diversity to the non‐cohesiveness of society, as reflected partly in the prevalence of mistrust, the divergence in preferences for public goods and redistributive policies, and the degree of fractionalization and polarization across ethnic, linguistic, and religious groups.




Open Book

Ashraf, Quamrul, Oded Galor, and Marc Klemp, "The Out of Africa Hypothesis of Comparative Economic Development: Common Misconceptions" (December 2018)

Ashraf, Quamrul, Oded Galor, and Marc Klemp,  "Interpersonal Diversity and Socioeconomic Disparities Across Populations: A Reply to Rosenberg and Kang" (December 2018

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