When ever they felt like it
When ever they felt like it
because they wanted to
to maintain "civilization" yes would be the answer. --civilization: a place with order.
It has a humid subtropical climate
Complex irrigation systems.
One major trend in early civilization and lifestyles was the organization of a complex institutional government and a definite social hierarchy.
to honor their rulers and please their gods
Mountain ranges & deserts
the rivers
the rivers
The occupied fertile river valleys, which gave them the surplus produce on which civilisation could develop.
An early civilization began there,and Chinese culture today evolved from that ancient beginning