Aliens and the Ancient Sumerian Culture

The Sumerians developed one of the earliest civilizations on earth (3500-1750 B.C.), but the existence of such a people and civilization was not even suspected until the middle of the 19th century.  People had long known about the Babylonians, since the ancient Egyptians, Hebrews, and Greeks had all come into contact with them and written about them. But no one knew that the Sumerians  had preceded the Babylonians and had developed the writing, religious, and agricultural systems which the Babylonians adapted and modified later.