How did the sumerians adapt to their environment to eventually create a farming surplus?

The sumerians lived in Mesopotamia in the Middle of two rivers, the Tigris and the Euphrates. While the soil was very fertil and productive, living between two rivers brought unexpected floods that caused great damage to the crops. The Sumerians eventually invented a system of ditches and irrigation to learn to control the flow of the rivers.

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a drastic rise in oil prices ended decades of postwar.