Explain the relationship between the establishment of early civilizations in river valleys and societal development.

The causes of the growth and decline of civilizations, and their expansion to a potential world society, are complex. However, civilizations require not only external advances to prosper, but also the maintenance and development of good social and ethical relationships usually grounded in religious and spiritual norms.

Ancient civilizations relied on floodwaters for farming. The floods deposited silt, which enriched the soil. People built irrigation systems and drainage ditches to divert the water to the agricultural fields, which allowed them to farm year-round. Year-round farming resulted in a food surplus, which lead to increased time for societal development.

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