Across the Iranian plateau after about 3500 BC, towns sprang up whose prosperity depended on trade. Some seem to have been dominated or controlled by the Sumerian or Elamite states, while others acted independently but in close association with Sumer and Elam.
A clear picture of such a relationship emerges from some of the Sumerian texts, such as 'Enmerkar and the Lord of Aratta', in which we can see that both threats of military action and offers of hefty bribes or payments were employed by the Sumerians to ensure the supply of desired materials and commodities.
Tepe Yahya, 600 miles (1,000 km) from the Elamite capital of Susa, combines a large native settlement with a small foreign presence: a large administrative building with both Elamite and Sumerian bureaucratic trappings, such as seals in Elam's early script (Proto-Elamite) and Sumerian bevelled rim bowls.
These towns functioned both as collection points for locally available materials and as transit points in the trade in materials from further afield. Often they developed particular specializations.
Tepe Yahya, for example, was a major manufacturing centre in the locally abundant steatite (soapstone) and chlorite (a green stone), producing vessels exported both to Elam and Sumer in the west and to the settlements of the Indus and the Indo-Iranian borderlands in the east.
