Who are the people who established the worlds first civilization known as

The earliest civilizations that arose in the world developed in the late fourth and the third millennia BC in parts of Asia and north Africa. The three large alluvial systems of the Tigris-Euphrates, the Nile and the Indus supported three great ancient civilizations. Other urban communities also arose during this time. For example, settlement mounds known as tells or tepes, occur in almost all major valleys between Iraq and Pakistan in one direction and between the Caspian Sea and the Indian Ocean in the other and many that have been explored are known to have been occupied in the same period. However, unlike the great civilizations of Egypt, Mesopotamia and Indus, these communities did not form part of a unified economic system, and these small units, though clearly able for a time to support large, wealthy and organized societies, were much weaker than the vast civilizations of the alluvial lowlands