How did early civilizations develop?

Well, it depends on how early you mean. Out of the Neolithic Stone Age, most civilizations developed and flourished near rivers. The further from a water source like that, the less likely they would survive.

However, besides that, everything was mostly based upon technology and intuitive thinking. For example, the Sumerians were carved into near extinction because of the Hittites and their discovery of the strength of steel weapons. And in Kemet (Egypt), the people there were put into slavery by the Sea People (said to be early Greeks) with their use of the horse.