In the period 5000-4000 BC much of Mesopotamia shared a common culture, called Ubaid after the site where the evidence for it was first found. The culture, which is characterized by a distinctive type of pottery, had its origins on the flat alluvial plains of southern Mesopotamia (ancient Iraq). Indeed, it was during this period that the first identifiable villages developed in this region, where people farmed the land and fished the rivers and sea (Persian Gulf).
Some scholars suggest that before the Ubaid period the water level in the south had been too high for permanent settlement. Increasingly, however, some of these new southern settlements became focused on monumental buildings, such as at Eridu and Uruk. Specific burial practices have also been found at Eridu and Ur along with distinctive clay figurines of humans with lizard-like heads.
The Ubaid culture spread north across Mesopotamia gradually replacing the Halaf culture. Ubaid pottery is also found to the south, along the west coast of the Persian Gulf, perhaps transported there by fishing expeditions. There is much continuity between the Ubaid culture and the succeeding Uruk period when many of the earlier traditions were elaborated, particularly in architecture.