Wikipedia 10K Redux by Reagle from Starling archive. Bugs abound!!!
The first cities started developing in southern Mesopotamia during the 4th millenium BC. With these ties of religion began to replace ties of kinship as the basis for society. Each city had a patron god, worshipped in a massive central temple called a ''ziggurat'', and was ruled by a priest-king (''ishakku''). Society became more segmented and specialized and capable of coordinated projects like irrigation and warfare. Along with cities came a number of advances in technology. By around 3000 BC, writing, the wheel, and other such innovations had been introduced. By now the SumerianPeoples of south Mesopotamia were all organized into a variety of independent CityState''s'', such as Ur and Uruk, which by around 2500 BC had begun to coalesce into larger political units. By accomodating the conquered people's gods, religion became more polytheistic and government became somewhat more secular; the title of ''lugal'', big man, appears along side the earlier religious titles, although his primary duty is still the worship of the state gods. Parallel developments were meanwhile occuring in Egypt, which by 3100 BC had been unified to form the OldKingdom, and amongst the peoples of the IndusValley in north-western India. All of these civilizations lie in fertile river valleys where agriculture is relatively easy once dams and irrigation are constructed to control the flood waters.