The Sumerian language still keeps the prestigious position of being the first ever written language. In this paper there are some presented linguistic data and examples, suggesting that the Sumerian is not a language isolate, as it is regarded so far, but that it may be classified as an r-Altaic language of the Bolgar branch. A proposed methodology for deducing such an inference is also presented, along with the outcomes of its application in the form of thirty-nine phonological rules.