The communities of the Urban Revolution differed from the larger neolithic villages out of which they had grown in many ways, but two were to be particularly important for the course of the future. The first was the development of a new basis for community. The extended family had been the biological offspring of the head of the group and so the members were united by ties of blood. Members of a hunting band of clan traced their descent from some common ancestor and so felt that they, too, were related by blood. On those occasions when clans consolidated into a tribe, they probably had, as modern clans have, some legends about the beginning of the world to explain their special relationship with each other. Each of the scattered neolithic communities likely had a deity from whom it traced its origin, and the worship of that deity acted to affirm community solidarity.
This was not possible with the advent of the Urban Revolution, since these villages and their inhabitants were absorbed into a new central settlement, and their ties of kinship became of less importance in this new and larger group. One of the tasks of the professional priesthood that emerged was to provide a cosmogony and theogony that explained the origins of the universe and the birth of the hierarchy of gods that ruled over it, and to provide a rich and impressive ritual exalting those gods. From what we know of the early cities of Sumeria, the rulers convinced their people to construct large pyramidal temples, called ziggurats, in the center of the city and to proclaim that one of the ruling gods or goddesses made their home there.
The logic was simple enough. If the god lived in your city, then that god ruled your city through his priesthood, and you and your neighbors were that god's chosen people. The ties of kinship were not eliminated of course, but existed within this larger and more potent association.
The limitations of blood-kinship were transcended at this point, and there was no longer a close limitation on the size to which a human community could grow. in the course of time, they grew upon the boundaries of their lands impinged upon those of neighboring urban centers, and still they grew. The ruler of the city, the servant of the god, was expected to provide for the god's people, and this led to full-scale warfare between the new urban centers. It became necessary for the priest king to collect, arm, and train young men as soldiers, to direct the people in surrounding their cities with strong defensive walls ad in building fortresses to protect their lands. One might imagine that such wars were implacable affairs, since the warriors were not fighting simply for their lives or property but for the life of their god, the embodiment of their entire community.
It may have been in order to mitigate the savagery of such warfare but, in any case, the nature of such conflict began to change. The victors did not destroy the temples and idols of the defeated, but to allow them to continue to worship their traditional deities, although acknowledging the superiority of the deity of their conquerors. The priest-kings also had to alter their character. Up to this point, they had held the title of ishakku, "steward of the god", but they could no longer be simply the steward of their city's god when they were ruling several cities each with its own deity. In the inscriptions of the time, their title becomes that of lugal, or, more simply, "king." With this development, the political organization of the city-states became secular and, to a great extent, independent of religious or kinship associations. There was no longer a maximum size to human social organizations, and an age of empires was now possible.
It is important to note that this development was not universal. Such empires arose in the Near East with the Akkadians and Babylonians, somewhat later in the Nile River valley of Egypt, in the great cities of Harappa and Mohenjo-daro of the Indus River valley, and perhaps still later yet with the Shang and Chou of the Yellow River valley of China. Much of the rest of the world continued to exist in small city states or tribal groups.
Continuing with the University of Minnesota modules, you may cover Harappa in the valley of the Indus River, and the Shang civilization of the Yellow River of China.
Shang China is not yet well represented in web sites, but the University of Wisconsin's course -- Art History 370 -- offers a wide selection of Shang art. China is useful as a guide to the chronology of early Chinese civilization.