The Out-of-India Theory
Here is a link to Professor Masaaki Kimura's page who claims to have found unusual artifacts, carvings and quarry marks in the ruins that would seem to authenticate them:
Samuel Noah Kramer asserts that the Sumerian people, who called themselves the “black-headed people,” were a Nomadic people who moved about. Where they came from is not really known-yet. However, many anthropologists are able to trace some of their roots to the Tamil people from Tamil Nadu in southern India due to similarities in language. This suggests the Sumerians probably originated in India as Tamils who established colonies and pyramid cities in China - then, traveled westwards into Mesopotamia to found the Sumerian civilization. This is generally known as the “out-of-India” theory.