Proto-Euphratean was considered by some Assyriologists (for example Samuel Noah Kramer), to be the substratum language of the people that introduced farming into Southern Iraq in the Early Ubaid period (5300-4700 BC).
Benno Landsberger and other Assyriologists argued that by examining the structure of Sumerian names of occupations, as well as toponyms and hydronyms, one can suggest that there was once an earlier group of people in the region who spoke an entirely different language, often referred to as Proto-Euphratean. Terms for "farmer", "smith", "carpenter", and "date" (as in the fruit), also do not appear to have a Sumerian or Semitic origin.
Linguists coined a different term, "banana languages," proposed by Igor Dyakonov and Vladislav Ardzinba, based on a characteristic feature of multiple personal names attested in Sumerian texts, namely reduplication of syllables (like in the word banana): Inanna, Zababa, Chuwawa, Bunene etc. The same feature was attested in some other unclassified languages, including Minoan. The same feature is allegedly attested by several names of Hyksos rulers: although Hyksos tribes were Semitic, some of their names, like Bnon, Apophis, etc. were apparently non-Semitic by origin.
Rubio challenged the substratum hypothesis, arguing that there is evidence of borrowing from more than one language. This theory is now predominant in the field (Piotr Michalowski, Gerd Steiner, etc.).
A related proposal by Gordon Whittaker is that the language of the proto-literary texts from the Late Uruk period (c. 3350–3100 BC) is really an early Indo-European language which he terms "Euphratic".
- История древнего Востока, т.2. М. 1988. (in Russian: History of Ancient Orient, Vol. 2. Moscow 1988. Published by the Soviet Academy of Science), p. 229.
- История древнего Востока, т.2. М. 1988. (in Russian: History of Ancient Orient, Vol. 2. Moscow 1988. Published by the Soviet Academy of Science), chapter III.
- Whittaker, Gordon (2008). "The Case for Euphratic" (PDF). Bulletin of the Georgian National Academy of Sciences. Tbilisi. 2 (3): 156–168. Retrieved 11 December 2012.
- Rubio, Gonzalo “On the alleged pre-Sumerian substratum,” in Journal of Cuneiform Studies 51 (1999): 1-16