The needs of a large, complex society led to further innovations, or new ways of doing things. The need to mark boundaries for farming in Sumer led to a unit of land measurement the Sumerians called the iku. Today we call it the acre.
The need to measure wheat and barley harvests established the quart as a basic unit of measurement. The need to carry trade goods up the river led people to build cargo boats with sails. The need to keep a record of ownership, taxes owed, and trade led to one of the Sumerians' greatest innovations writing.
At first the scribes of Sumer marked picture symbols in pieces of wet clay and let the clay dry They then attached these pieces to baskets as tags to identify the contents and the owner. By about 2000 B.C. the Sumerians had developed their symbols into a complete writing system. This system was based on cuneiform , or wedge-shaped symbols. Each symbol stood for a different syllable and was based on a spoken sound.
To make the cuneiform marks in the soft clay, Sumerian scribes used a stylus, which they made by sharpening the end of a piece of reed. The clay was then baked or left in the sun until it was hard. Cuneiform writings that have been found give a record of Sumer's growing economic activity and way of life.
What innovations did the Sumerians develop?