of southern Mesopotamia." These ideas about the nature of the Ubaid style phenomenon did not last. The term "Ubaid" is still used, but its meaning has changed over time.

Joan Oates demonstrated in 1960 that the Eridu and Hajji Muhammed styles were not distinct at all. Instead, they were part of the greater Ubaid phenomenon. She proposed a chronological framework that divides the Ubaid period in four phases. Other scholars later proposed two more phases, zero and