All this happened, more or less.

it was the particular climatic conditions of Mesopotamia - where irrigation could markedly improve crop yiedls and where there is enough water available ( but in the wrong place) to allow this development [communal irrigation system] fairly easily and obviously. The crucial point wsa that though the land was now habitable, there was still so much water available that nearly every arable plot had easy and direct access to it. "This fact ... must have produced a "paradise", with multiple, high-yeld harvests each year'(check quote). An added factor was that the southern alluvial plains of Mesopotamia were lacking in other commodities, such as timber, stone, minerals, and metals. The food supply of this 'paradise' could be traded for these commdities, making for a dense network of contacts, and provided conditions for the development of specialist workers in the cities themselves. diverse population, going beyond simple kin groups. This was an exciting advance: for the first time people could become involved in activites not directly linked with food production. Yet this development would have raised anxiety levels: citizens had to rely on others, not their kin, for essentials. ... For these same reasons, religion may well have become more important in cities than in previous configurations. Ibid. p. 75