They developed a new Culture that lasted from about 5,600 to 3,500 BC. It was called Ubaid, after the settlement of the same name. Early in the Ubaid period the area contained relatively large, populous settlements, as centres, surrounded by villages. The first temples were built in this period in South Mesopotamia that needed an administration to operate them. These were precursors to the organisations that had to be developed to run the earliest urban states. The social organization moved from predominantly egalitarian, with little “ranking” and mainly shared workload, to hierarchical with the rise of an elite, inherited chieftains and craft specialization. This was possible because of the irrigation-dependant surpluses of food (mainly wheat, barley and lentils).

The Ubaid Culture was the precursor to what we now call the Sumerian Culture that eventually came to be regarded as the first Civilization in the world. The name Sumer was not contemporary with the culture; it was the Akkadians who followed them who gave the name to the language and people of this region.  It is not that obvious why the people of Southern Mesopotamia became the lead social organization at this time, as settlements such as Jericho were also developing quickly. Clearly, given the characteristics of the region, the lack of local sources of raw materials and the irrigation-dependant agriculture, they were forced to trade with other regions, assisted by the often-strategic position of their settlements. It is most likely that the need to trade, with its attendant requirements of transport and communications, not only led to economic strength but also to strengthening social interaction and cohesion, including religion, which meant large groups of people worked cooperatively with common aspirations. This would require the development of economic and organizational systems in support. Another difference between the innovation and development of some contemporary cultures compared with the Ubaid Culture was that they were more sporadic and subsequently disappeared, whereas the Ubaid Culture had a continuity that led to more systematic advancement.

The Ubaid Culture progressed and by about 4500 BC the people lived in a number of relatively independent settlements, each consisting of a small, now well-fortified city, with a population of a few hundred to a few thousand, and its surrounding area. At the heart of each city was the mud brick temple on a high platform, usually dedicated to a specific god, and some contained other large public buildings (notably large granaries) and other buildings making up ceremonial centres for the smaller settlements in the surrounding area. This centralized ritual is very different from the household-based ritual in Catal Huyuk. It appears that organised ritual or religion, based on the temple populated with priests, held as much sway as the rulers and their councils of elders. In these early days and later in “Babylonia” much attention was paid to religious buildings and ritual objects. The people were polytheist, worshiping many gods – as many as 1,000. The temple area was surrounded by larger houses for the elite, other houses were densely packed with narrow alleys between. A significant difference in the building technology between Ubaid and particularly Egypt was the lack of stone in South Mesopotamia. This meant buildings had to be designed with mud bricks in mind, fired bricks were used where necessary and new methods devised for roofing.

Their vital irrigation systems had to be protected, so armies were trained, victories celebrated and treaties agreed with neighbours. Although they shared a common Culture, interstate warfare was a preoccupation. Because of this a great deal of art was dedicated to military prowess. By this time the organization existed to support an advanced stage of specialized craftsmen. Food such as grain was pooled and rationed out by the state to those who no longer worked in the fields. Apparently the temples were involved in the central storage and distribution of food and trade goods, and a burgeoning bureaucracy was developing.