苏美尔语
The Sumerian language is one of the earliest known written languages. The "proto-literate" period of Sumerian writing spans c. 3300 to 3000 BC. In this period, records are purely logographic, with phonological content. The oldest document of the proto-literate period is the Kish tablet. Falkenstein (1936) lists 939 signs used in the proto-literate period (late Uruk, 34th to 31st centuries).