The enhanced complexity of city life in Mesopotamia also increased the need for regulation. We have evidence for a system for rewards and punishments, a central administration and taxation. All these institutions required efficient bureaucracy, which in turn prompted the invention of the first script around 3400 BC.
Initially this script was only used to record inventories and commercial transactions. Only later was the script also used for literature. The script consisted of pictograms pressed in clay and was later evolved into wedge-shaped marks known as cuneiform. .
During its entire history, only a small percentage of the population of Sumer was able to read and write and it was considered a high status job.
"The Great World History Book"