The Sumer civilization in southern Mesopotamia – in the delta between the Tigris and Euphrates rivers – started around 5000 bce. The earliest settlers drained the marshes for agricultural land. They started industries, including weaving, leather work, masonry, metal work, and pottery, and developed trade.
Southern Mesopotamia is an odd spot for civilization to be cradled. The flat, river-made land of Sumer had no minerals, no stone. Typical summer temperature was 40 °C, often climbing to 50 °C. Annual rainfall averaged 150 mm, and it was bone dry for 8 months of the year. Winter nights are shivering cold. Strong north winds deliver squally rainstorms. The melting snows of spring bring flash floods, which in bad years sweep everything away.
But the alluvial soil was rich. There was timber. Nearby was a great primeval forest, stocked with sturdy cedar.
The forest was felled as quickly as it could be, though that took 2 millennia, so great was the abundance. Thanks to such careless disregard for Nature, future generations were to inhabit a forbidding place.
The key to Sumer civilization came in water delivery. Sumer cities were the first to practice year-round intensive cultivation, with organized irrigation, mono-cropping, and specialized labor. The emergence of greater social organization was driven by the need for large public works to overcome the climactic challenge, and to exploit in an unsustainable way the agricultural potential. Like countless civilizations since, Sumer was bound to fail.
Inequality powered the Neolithic Revolution, which Mesopotamia and Sumer exemplified. However savage hunter-gathers had been to outsiders they were relatively egalitarian in sharing their bounty within the tribe.
Control of irrigation in Sumer created labor classes. Those in control of water profited from those who were not.
Sexual inequality took root with agrarian society. Men made women do much of the arduous work. While this may not have been much of a change from hunter-gatherers, settlements settled exploitative inequity as an acceptable norm. Religions helped in this regard.
By 3,500 bce Sumer was carved into a dozen city-states, divided by canals and boundary stones. Each was administered by a priestly governor or king, ruling under the aegis of a patron god or goddess of the city. Religion was ever the handmaiden of politics.