Sumerian linguistics

In Sumerian linguistic typology, Sumerian is classified as an agglutinative language with split ergativity. Ever since the decipherment of its written form, fully knowing Sumerian phonetics has proven difficult not only by the lack of native speakers, but also by the relative sparseness of linguistic data, the apparent lack of a closely related language, and the language isolate features of the writing system.

Linguistic origins
Archaeologists have speculated that the original speakers of ancient Sumerian may have been farmers, who moved down from the north of Mesopotamia after perfecting irrigation agriculture there. The Ubaid period pottery of southern Mesopotamia has been connected via Choga Mami transitional ware to the pottery of the Samarra period culture (c. 5700 – 4900 BC C-14) in the north, who were the first to practice a primitive form of irrigation agriculture along the middle Tigris River and its tributaries. The connection is most clearly seen at Tell Awayli (Oueilli, Oueili) near Larsa, excavated by the French in the 1980s, where eight levels yielded pre-Ubaid pottery resembling Samarran ware. According to this theory, farming peoples spread down into southern Mesopotamia because they had developed a temple-centered social organization for mobilizing labor and technology for water control, enabling them to survive and prosper in a difficult environment.

Substrate language debate
The Sumerians spoke a language isolate, but a number of linguists have claimed to be able to detect a substrate language of unknown classification beneath Sumerian because names of some of Sumer's major cities are not Sumerian, revealing influences of earlier inhabitants. However, the archaeological record shows clear uninterrupted cultural continuity from the time of the early Ubaid period (5300 – 4700 BC C-14) settlements in southern Mesopotamia. Therefore, some scholars contest the idea of a Proto-Euphratean language or one substrate language; they think the Sumerian language may originally have been that of the hunting and fishing peoples who lived in the marshland and the Eastern Arabia littoral region and were part of the Arabian bifacial culture.

Phonology
Sumerian phonology is flawed and incomplete because of the lack of native speakers, the transmission through the filter of Akkadian phonology and the difficulties posed by the cuneiform script. There is relatively little consensus, even among reasonable Sumerologists, in comparison to the state of most modern or classical languages. Verbal morphology in particular is hotly disputed. In addition to the general grammars, there are many monographs and articles about particular areas of Sumerian grammar, without which a survey of the field could not be considered complete. As I.M. Diakonoff observes, "when we try to find out the morphophonological structure of the Sumerian language, we must constantly bear in mind that we are not dealing with a language directly but are reconstructing it from a very imperfect mnemonic writing system which had not been basically aimed at the rendering of morphophonemics".

Affiliation attempts
Though Sumerian is a language isolate,  it has been the subject of much effort to relate it to a wide variety of languages. Because it has a peculiar prestige as the most ancient written language, proposals for linguistic affinity sometimes have a nationalistic background. Such proposals enjoy virtually no support amongst linguists because of their unverifiability. Sumerian was at one time widely held to be an Indo-European language, but that view later came to be almost universally rejected.
 * Proposed linguistic affiliations:


 * Kartvelian languages (Nicholas Marr)
 * Munda languages (Igor M. Diakonoff )
 * Dravidian languages (see Elamo-Dravidian )
 * Uralic languages (Simo Parpola ) or, more generally, Ural–Altaic languages (Simo Parpola, C. G. Gostony, András Zakar, Ida Bobula )
 * Basque language (Aleksi Sahala )
 * Nostratic languages (Allan Bomhard )
 * Sino-Tibetan languages, specifically Tibeto-Burman languages (Jan Braun, following C. J. Ball, V. Christian, and K. Bouda )
 * Dené–Caucasian languages (John Bengtson )

In the Proto-Euphratean language hypothesis, it’s proposed that a Euphratic influence was exerted on Sumerian as an Areal feature, especially in the form of polysyllabic words which appear "un-Sumerian"–making them suspect of being loanwords–and are not traceable to any other known language. There is little speculation as to the affinities of this substratum language, or these languages, and it is thus best treated as unclassified. Researchers such as Gonzalo Rubio disagree with the assumption of a single substratum language and argue that several languages are involved. A related proposal by Gordon Whittaker is that the language of the proto-literary texts from the Late Uruk period (c. 3350–3100 BCE) is really an early Indo-European language which he terms."
 * Proto-Euphratean language hypothesis

Jens Høyrup suggests that the Sumerian language descended from a late Paleolithic creole language (Høyrup 1992). However, no conclusive evidence, only some typological features, can be found to support Høyrup's view.
 * Høyrup’s hypothesis