qnli question: How many levels of pre-Ubaid pottery were excavated by the French in the 1980s? sentence: The Ubaid 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.