Which is a reason sumer declined as a civilization? sumerian city-states fought each other. sumerian rulers outlawed religion. the climate changed drastically. the tigris and euphrates rivers dried up.

I believe the answer is: Sumerian rulers fought to gain territory

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Because of the conflict that happened between sumerian rulers, The territory of the Sumerian empire started to be divided/separated into smaller empires. This make it much more easier for opposing empire or barbarian to conquer them and pick them apart, which lead to the decline of Sumer civilizations.

a historian who compares the expansion of political systems to the expansion of economic systems to the expansion of economic systems is organizing history by theme.

hope this : d

i think they would live in caves or natural tunnels