When did the first civilizations develop in Mesopotamia?

The area known as Mesopotamia has history dating back to the Pre-Pottery Neolithic A period, between 10,000 and 8700 BCE. Records of early dynastic kings in lower Mesopotamia begin in the middle of the 3rd millenium BCE. Bronze Age Mesopotamia (~2900 BCE to 12th/11th centuries BCE) is considered to be the cradle of civilization in the West. Despite Babylon's fall in 539 BCE, the area has always been occupied by at least one or more important groups.