The ancient Sumerian language has been categorized as what type of language?

The language of ancient Sumer (in Mesopotamia, modern-day Iraq) is one of the earliest known languages and is currently accepted by linguists as a language isolate. The earliest written examples date back to around 2900 BC, the time period between 2900 and 2600 BC are considered Archaic Sumerian, when the earliest forms of inscriptions with linguistic content are seen. Prior to the Archaic period was the proto-literate period (roughly between 3300 BC and 2900 BC), when proto-cuneiform pictographic characters were used, that later developed into the cuneiform that was adopted by other Near East and Mesopotamian cultures, including Akkadian and Hittite languages.

Sumerian is considered a language isolate, since it is well enough documented that if any modern relatives of the language exist, they would be easily recognized as related. Around 1700 BC Sumerian fell out of common use, and used as a liturgical and classical language for artistic and scholarly purposes until about 100 AD.

Different origins of Sumerian abound, in one argument it has been considered descended from a late prehistoric creole language. Other proposed sources attempted to link the language with unrelated languages such as Uralic, Austroasiatic and Dravidian languages. These proposals have little support among linguists and can be seen as fringe theories.