 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.Others have suggested a continuity of Sumerians, from the indigenous hunter-fisherfolk traditions, associated with the bifacial assemblages found on the Arabian littoral.Juris Zarins believes the Sumerians may have been the people living in the Persian Gulf region before it flooded at the end of the last Ice Age.