This system would be greatly expanded during the subsequent Uruk IV Period which began around 3900 BC, when the ancient Sumerian religious centre of Eridu was gradually surpassed in size by the nearby city of Uruk.
The Late Ubaid also saw the beginning of the Chalcolithic Period, or Copper Age (from the Greek khalkos, copper, and lithos, stone), in which the use of early metal tools appeared alongside traditional stone tools.
The archaeological transition from the Ubaid period to the Uruk period is marked by a gradual shift from painted pottery which was domestically produced on a slow wheel, to a great variety of unpainted pottery which was mass-produced by specialists on fast wheels.
The Ubaid had paved the way in southern Mesopotamia for the development of full-blown civilisation over the succeeding millennium.
As the Middle Ubaid got underway, the farmers began to channel small canals towards their crops, saving themselves the labour of carrying pots of water. The canals were developed over the centuries, becoming more and more sophisticated and extensive. Alongside them, small settlements and villages developed into bigger communities, and labour became centralised. Farming reached a level of efficiency which allowed some of the inhabitants in the growing villages time to devote to other pursuits.
Large villages gradually developed into small cities in a period of rapid urbanisation. Ubaid culture spread rapidly outwards to displace the earlier Halaf culture in northern Mesopotamia, although there was a gap between the decline of the one and the arrival of the other. Ubaid goods also began to appear along the Persian coast to the south, in Arabia, revealing the spread of a trading network outwards from southern Mesopotamia. Fishing boats also made their first appearance at this time.