The Ancient Sumerians were probably the most advanced civilization of the history of mankind according to most findings out there. They first arrived in Mesopotamia by ships and knew to settle in Tigris and Euphrates, as they were the best locations to live on.
They were most likely the first ever civilization known to use the bike, build an irrigation system, and were probably the first to create their written language.
We don’t know exactly where they come from, but some people think they originated from South India.
According to their ancient books, the ancient Gods attacked humans because they thought it to be too imperfect and impure. They created thunderstorms and other cataclysmic upon humanity.
Enki, their only supporter, helped humanity by telling Ziusudra to build an enormous ship and get all of the Sumerians on it.