section_path: Population
section_name: Population
paragraph_text: Population
  
  Uruk, one of Sumer's largest cities, has been estimated to have had a population of 50,000–80,000 at its height. Given the other cities in Sumer, and the large agricultural population, a rough estimate for Sumer's population might be 0.8 million to 1.5 million. The world population at this time has been estimated at 27 million.
  
  The Sumerians spoke a language isolate. A number of linguists have claimed to be able to detect a substrate language of unknown classification beneath Sumerian, because names of some of Sumer's major cities are not Sumerian, revealing influences of earlier inhabitants. However, the archaeological record shows clear uninterrupted cultural continuity from the time of the early Ubaid period (5300–4700 BC C-14) settlements in southern Mesopotamia. The Sumerian people who settled here, farmed the lands in this region that were made fertile by silt deposited by the Tigris and the Euphrates.
  
  Some archaeologists have speculated that the original speakers of ancient Sumerian may have been farmers, who moved down from the north of Mesopotamia after perfecting irrigation agriculture there. The Ubaid period pottery of southern Mesopotamia has been connected via Choga Mami transitional ware, to the pottery of the Samarra period culture (c. 5700 –4900 BC C-14) in the north, who were the first to practice a primitive form of irrigation agriculture along the middle Tigris River and its tributaries. The connection is most clearly seen at Tell el-'Oueili near Larsa, excavated by the French in the 1980s, where eight levels yielded pre-Ubaid pottery resembling Samarran ware. According to this theory, farming peoples spread down into southern Mesopotamia because they had developed a temple-centered social organization for mobilizing labor and technology for water control, enabling them to survive and prosper in a difficult environment.
  
  Others have suggested a continuity of Sumerians, from the indigenous hunter-fisherfolk traditions, associated with the bifacial assemblages found on the Arabian littoral. Juris Zarins believes the Sumerians may have been the people living in the Persian Gulf region before it flooded at the end of the last Ice Age.