Sumerian script, the earliest known form of writing among prehistoric writing systems, was first used on clay tablets for accounting purposes. | Although the earliest Sumerians engaged in commercial activity and practiced accounting, they were not as literate as people in other parts of the prehistoric world. | Archaeologists have discovered that literacy was developed in several parts of the world, including ancient Mesopotamia. | Archaeological detective work has revealed the commercial accounting practices of the Sumerians of ancient Mesopotamia and provided a written record of their intense commercial activity. |