CopperAge

Around 4000-3500 BC the first cities appeared among the SumerianPeoples of Mesopotamia.  With these came a new societal structure.  Ties of kinship no longer sufficed to hold communities together, and were replaced by religion.  Each CityState had a patron god, to whom a massive central temple (ziggurat) was dedicated, and was ruled by a priest-king (''ishakku'').

The development of cities led to increased specialization and enabled people to take on bigger projects.  Kings were responsible for coordinating efforts like irrigation and warfare, which increased considerably in scale.  By around 2500 BC cities had begun to dominate each other, and by accomodating their subject's gods began to become slightly more secular in character, and eventually Mesopotamia was united under the empires of Akkad, Ur, and OldBabylonia.

Meanwhile parallel developments had occured in Africa and India.  Egypt was united to form the old kingdom around 3100 BC, the country that left us the pyramids, and after a brief interlude became the middle kingdom centered at Thebes.  And a relatively poorly known, but nevertheless highly advanced, urban civilization grew up at centers like Harappa in the IndusValley.

The urban societies of this era emerged along with many new advances, most notably writing.  However, in terms of tools things did not progress technologically to any great degree.  Copper smelting developed, but the metal is fairly expensive and brittle, and most implements remained tipped with stone, and farming remained restricted to the fertile river valleys where these civilizations had developed.

Things started changing around 2000 BC.  Civilization began to spread to the surrounding hills where agriculture necessarily depended upon rainwater, and new civilization centers began to develop around the older ones: the HittitePeoples arrived in Anatolia (Turkey), cities developed among the CanaanitePeoples of Syria-Palestine and the MinoanPeoples of Crete.  This process intensified around 1600 BC, when new immigrants with bronze technology overtook the older civilization centers.