Comparative and Competitive Advantages

Taken together, the various environmental and geographic advantages just noted had important consequences for processes leading to the Sumerian takeoff. On the one hand, advantages in productivity and resilience of their environmental framework meant that, in aggregate, elites in Uruk centers controlling the various ecotones that comprised the fourth-millennium alluvial landscape of southern Mesopotamia could extract larger (agricultural) surpluses per unit of labor than their counterparts elsewhere, and they could do so with greater reliability and predictability. On the other hand, the inherent advantages of water transport provided by their geographical framework meant that Uruk elites could concentrate and deploy the larger surpluses possible in their dependent hinterlands at much lower cost than their peripheral competitors. When combined, these parallel advantages meant that alluvial societies were subject to looser Malthusian constraints (chap. 3) than their rivals elsewhere. Of equal importance, water transport also allowed Uruk elites to procure nonlocal resources and information from a much vaster area, and again at much lower cost, than their landlocked contemporaries elsewhere. In addition, and equally crucially, ease of transport meant that the extent of the dependent hinterlands that Uruk elites could dominate would naturally be larger than those that rivals away from the river could control, and that the number of laborers that Uruk elites could command would be commensurably greater than the number deployable by contemporary rivals elsewhere.

Under conditions such as these, as Ricardo and his intellectual successors remind us, trade is the logical outcome. Specifically, I see imbalances in competitive advantage between southern Mesopotamia and neighboring polities as promoting evolving patterns of trade that are central to understanding the location of Uruk centers within the alluvial Mesopotamian ecosystem and the patterns of growth of those centers. We now turn to a discussion of those patterns.