Origins of Writing. Beginning around the eighth millennium B.C.E., Mesopotamians used small clay tokens to represent units or aggregate units of various entities such as animals or jars of grain. Around the middle of the fourth millennium B.C.E., more-complex methods were developed to keep track of the ever-increasing numbers of sheep and cattle and the vast quantities of grain and other commodities entering and leaving temple-owned farms and warehouses. The most significant of these developments, appearing about 3200 B.C.E., was proto-cuneiform, the world's first writing system. Mesopotamians wrote on clay tablets with a stylus made from a reed that was trimmed to form a round, pointed, or sloping end. These writing materials were readily available in the river valleys of southern Mesopotamia. At first, signs were incised into the surface of the clay, but soon...