Trading centers grew into cities.

Agricultural practices improved.

Not everyone was needed for farming.

Some people specialized in a trade.

They used it for religious worship.

They used it as a home for slave labor.

They used it as the king's home.

They used it to store important government records.

a single city-state ruled by priests

a collection of many small city-states, each ruled by its own king

a collection of many small city-states, all ruled by one central king

a single city-state ruled by one king

They used epics.

Aliens created them.

They used a system of writing.

They used slave labor.

They worshiped by giving offerings.

They worshiped in a temple.

They all had an "Aunt Polly."

They believed in many gods.