“Unfortunately, very little survives of Sumerian literature from the third millennium B.C. Several fragmentary tablets contain references to a time before the pantheon of the gods, when only the Earth (Sumerian: ki) and Heavens (Sumerian: an) existed. All was dark, there existed neither sunlight nor moonlight; however, the earth was green and water was in the ground, although there was no vegetation. More is known from Sumerian poems that date to the beginning centuries of the second millennium B.C. – factsanddetails.com