Explain how humans evolved from small, nomadic groups into early civilizations, c. 200,000-1000 BCE, including a discussion of the roles of...

As the evolution of human groups from small bands of hunter-gatherers to urban civilizations generally took place before the invention of writing, we must rely primarily on archaeological evidence.

The so-called "neolithic transition" consisted of several inter-related phenomena. Perhaps the most important was the development of agriculture as it simultaneously increased food production and created a strong motive for settling in a fixed locale. The food surplus provided by agriculture allowed for specialization of labor; communities could afford to support people who were not themselves focused on food production. This meant a quantum leap in technology, including improvements in pottery and metallurgy which in turn increased the efficiency of food production and preparation. 

Both Egypt and Mesopotamia developed vast urban civilizations in this period. They were effectively theocracies in which centralized governments and religion worked together to create a social order. In both areas, the necessity of building complex irrigation systems for agriculture increased social cohesion. The surplus production also allowed for trade, first between agricultural areas and urban centers and later developing into vast trade networks. As trade flourished, systems of writing became important for communication over long distances.