Conversation so far:
why did river valleys became centers of civilizations
Civilizations developed around rivers because their waters provided places to hunt and fish. Also, as the rivers flooded, the lands around them became fertile.
what were the first river valley civilizations
Examples of early river valley civilizations include the Indus Valley Civilization, Ancient Egypt, Mesopotamia, and Chinese civilization along the Yellow River.
which was the earliest river valley civilization between the indus valley civilization, ancient egypt, mesopotamia, and chinese civilization along the yellow river
Mesopotamia was the earliest river valley civilization, starting to form around 3500 BC.
where is mesopotamia today
Mesopotamia was an ancient region corresponding to today's Iraq, mostly, but also parts of modern-day Iran, Syria and Turkey.

Question: when did the civilization fall
Self-contained rewrite: when did mesopotamia fall