The Sumerian literature is unique due to the fact that the Sumerian language itself is unique in its kind because it does not belong to any known linguistic root. Its appearance began with symbols of the things denoting it, then it turned with time to the cuneiform line, and later spread during the third millennium BC. All of them were in Mesopotamia, but hey were affected by historical events, so they lost much of their importance, and became the language of religious rituals, after the Semitic Akkadian language overcame them.