Why did separate city-states develop in sumer?

Answer 1

The Sumerian communities were called city states because there cities are so large that they are almost as large as a normal state but the are in dependent states.

Answer 2

At that period in time it was difficult to organize a larger empire. The bureaucracy required to maintain holdings far from direct control was not available. This led to control being limited to the distance a person could walk or run in a day's time (basically a city). Eventually, leaders like Sargon of Akkad were able to conquer multiple city-states and assemble small bureaucracies to help him administrate the landholdings, leading to the first empires.

Answer 3

Because Sumerian people first lived somewhere else. Because of little water they had some moved between the two rivers.

Answer 4

they were called sumerians.