Initial social complexity in southwestern Asia - The Mesopotamian advantage

The emergence of early Mesopotamian (Sumerian) civilization must be understood within the framework of the unique ecology and geography of the alluvial lowlands of the Tigris and Euphrates Rivers during the late 5th and 4th millennia B.C. The former gave Mesopotamian societies important advantages in agricultural productivity and subsistence resource resilience not possessed by contemporary polities on their periphery, while the latter gave them enduring transportational advantages. This material imbalance created opportunities and incentives that made it both possible and probable that early Mesopotamian elites would use trade as one of their earliest and most important tools to legitimize and expand their unequal access to resources and power. Given this, a still hypothetical (but testable) model is presented that accounts for the precocious socioeconomic differentiation and urban growth of southern Mesopotamia in the 4th millennium as social multiplier effects inadvertently set in motion by evolving trade patterns. This trade was first largely internal, between individual southern polities exploiting rich but localized ecological niches within the Mesopotamian alluvium during the Late Ubaid and Early Uruk periods. By the Middle and Late Uruk periods, however, inherently asymmetrical external trade between growing southern cities and societies at their periphery in control of coveted resources gained more prominence. In due course, import-substitution processes further amplified the one-sided socio-evolutionary impact on southern societies of these shifting trade patterns. Unequal developmental rates resulting from the operation of these processes over time explain why the earliest complex societies of southwestern Asia appeared in southern Mesopotamia and not elsewhere.