It was first used in Sumer in the late 4th millennium BC (the 'Uruk IV' period). Cuneiform writing began as a system of pictographs. In the third millennium, the signs became simplified and more abstract. Fewer characters were used, from about 1,000 in the early Bronze Age to about 400 in late Bronze Age (Hittite cuneiform). The system used a combination of phonetic, consonantal alphabetic (no vowels) and syllabic signs.