The ancient civilizations of Egypt and Mesopotamia were two of the oldest in the world, lasting for thousands of years from around 3500 BCE to 539 BCE. While the Egyptian civilization began along the Nile River in Africa, Mesopotamia's civilization began in the Middle East. During the rise and height of these societies, there were significant developments in social hierarchy, division of labor, writing, religion, and technology. This period also saw the unification of Upper and Lower Egypt in 3000 BCE and the rise of Sumerian city-states in Mesopotamia. With three floating chronologies, the Egyptian Chronology also relies on the chronologies of Mesopotamia, the Levant, and Anatolia.