was a resource-deficient area. Although it could produce a bounty of food
once irrigation systems were in place, Sumer had no deposits of metals or
useful stone, and its wood was unsuitable for heavy construction. Most of
what Sumer lacked could be found in sufficient quantities in the areas that
ringed Mesopotamia. Building an empire to incorporate these lands was not
a viable option until the late third millennium: the Sumerian cities could
not so much as unify themselves. The solution was long-distance trade. In
the highlands to the east in modern Iran, copper had been worked as early as
thefifth millenniumBCE, and by the third millennium silver was coming
from that direction as well. Beyond Iran was Afghanistan, from which tin
and precious stones reached Mesopotamia, some probably through directional
trade. The mountains to the north in Anatolia and the Caucasus were a
storehouse of metals, and copper also came from the opposite direction on
the eastern shores of the Persian Gulf. Syria and Lebanon to the west were a
source of cedar and other hardwoods as well as wine and olive oil.
Imports have to be paid for by exports, and determining what the
Sumerians used for this is somewhat tricky. They produced a surplus of grain
and other foodstuffs, such as dates, driedfish, and lard. The problem was
transportation, especially when goods had to be carried overland. Foodstuffs
are a bulky commodity, and a lot of grain would have been required to pay
for a rather small quantity of metal, not to mention precious stones. To make
matters even less clear, food is among the most perishable of items and thus
archaeologically invisible. Documentary evidence confirms that Mesopotamia
exported textiles in the form of woolen cloth and clothing as well as leather
products. Luxury goodsflowed in both directions. The temples and palaces
of Sumerian cities had great workshops that took in imported raw materials
and turned outfinely made jewelry, ceremonial and ritual items, weapons,
and aromatic oils. Much of this was intended for the local elite, but at least
some of it was exported with much value added. Over the years the
Sumerians were able to create a market for their own surplus production.
The consequence of this for the highland communities of Iran and other
peripheries was to accelerate the process of social stratification as local leaders
emerged to direct the production of Sumerian-bound exports and control the
distribution of imports from Sumer.
As the cities of Mesopotamia became larger, richer, more centralized, and
more complex, their needs expanded. Resources were sucked in from
increasing distances as older networks of exchange broadened and new ones
were created. Two systems evolved. In thefirst, trade expeditions, usually
armed and under the banner of a king or temple, were sent out on a sporadic
basis. The preferred way to trade was with partners with whom a relation-
ship was already established rather than wandering around dealing with
whomever one happened upon. In the second system, relay trade was used
across a succession of middlemen. Rivers, especially the Euphrates, func-
tioned as trunk lines for transporting goods with secondary linkages in the
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