5,000-3,500 B.C. – The Formative Period
Irrigation became more broadly utilized which facilitated settlement of the grassland areas. By 4,000, an economy was well-established in Susa (see map). Lowlands were not established in a substantial way until irrigation techniques had advanced to the point of insuring a consistent harvest and water-born transportation was able to supply the lowlands with raw materials.
Two cultures evolved: agriculture only in the lowlands and mixed agriculture and pastoralism of the grasslands areas. By 3,500 B.C. the area known as Sumer had grown significantly and created the world’s first urban environment. A good example of a Formative Period settlement is at Eridu, where reed and clay huts have been excavated. Date palm and fish were in the diet, along with cereals. Sheep and goats were herded. Pottery was excavated along with kilns.
The village organizations were chiefdoms and theocratic. Each village contained a temple.