The Lost Civilization Of The Sumerians
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, but a number of linguists have claimed to be able to detect a substrate language of unknown classification beneath Sumerian because the 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.