Babylonian mythology was local in origin; each of the gods had a particular city which was the seat of his worship, and it is probable that the idea of weaving the gods into a system, in which each should have his part to play, only had its origin at a later time. The antiquity of this mythology may be seen by the fact, that two thousand years before the Christian era it was already completed, and its deities definitely connected into a system which remained with little change down to the close of the kingdom.
It is probable that the gods were in early times only worshipped at their original cities or seats, the various cities or settlements being independent of each other; but it was natural as wars arose, and some cities gained conquests over others, and kings gradually united the country into monarchies, that the people of conquering cities should claim that their gods were superior to those of the cities they conquered, and thus came the system of different ranks or grades among the gods. Again, colonies were sent out of some cities, and the colonies, as they considered themselves sons of the cities they started from, also considered their gods to be sons of the gods of the mother cities. Political changes in early times led to the rise and fall of various cities and consequently of their deities, and gave rise to numerous myths relating to the different personages in the mythology. In some remote age there appear to have been three great cities in the country, Erech, Eridu, and Nipur, and their divinities Anu, Hea, and Bel were considered
