Early civilizations, such as those in egypt, sumer, and harappa, were all

These three civilizations were all centered around rivers that flooded regularly.

Explanation:

In ancient times, to prosper, civilization should be closer to rivers. Most important, it was necessary to understand how the floods work and, then, be adaptative to each situation. In the case of the civilzations that you asked:

- "the most famous structure by far at saqqara is djoser's step pyramid. dating from the 3rd dynasty (2667—2448 bc), it was the first all-stone complex ever built on earth."

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