"The Sumerians were a people who comprised one of Earth's oldest known civilizations (approx. 4,000 B.C.), located in southern Mesopotamia (Iraq/Iran). They were a non-Semitic people of unknown origin." (PoL)
The Cradle of our Civilization is to be found in Southern Mesopotamia, after the Great Floods, around 11,000 BC. Over a period of about 3,600 years, man became a farmer, and wild plants and animals were domesticated. Around 7,500 BC, pottery was invented. Around 6,000 BC, metallurgy made its entrance.
In that same area, the Sumerian civilization was the first real civilization to flourish after the Great Floods. It came into existence around 3,900 BC which is a 800 years before the Egyptian civilization, 1,500 years before the Minoan civilization, and almost 2,000 years before the Chinese and Indian civilizations (!). Sumeria would eventually split up in Babylonia and Assyria. The Sumerian civilization fascinates scientists, because it appeared out of nowhere, and reached an incredibly high level of technology, practically overnight. The Sumerians were the 'inventors' of writing, printing, architecture, mathematics, money, chemistry, medicine,... They had a textile and clothing industry, advanced agriculture, and cuisine. They had an efficient system of transportation, built the first schools, established the performing arts, created the first organized law-system...
The Sumerians themselves "claimed to have had the foundation of their civilization given to them by the 'DIN.GIR' - pure ones of the bright pointed objects, or people of the fiery rockets - or, in human terms, extra-terrestrials." (PoL). Earth's galactic history confirms that indeed, several alien races, such as the Sirians and the Lyrans, had frequent contacts with the Sumerians. In fact, there even were conflicts between the Sirians and the Lyrans about their mutual influences upon the Sumerians. In this context, I think it is interesting to have a closer look at Enki and Enlil, two of the leading Sumerian "gods." I believe Enki represents the Sirian energies, while Enlil probably represents the Lyran (and Pleiadian) presence. SEE Sumerian mythology for more information on the Sumerian Gods.
It is interesting to note that Hindu mythology, as well as the Greek, Hittite, Hurrian, Assyrian and Babylonian mythology, all tell stories that are copies of stories of Sumerian mythology. Even a lot of stories in the Old Testament, are copies of Sumerian stories. These stories came to the West in two ways: a) Sumeria => Babylon & Assyria (both had the same language: Akkadian, and lived next to one another from 1900 BC till 614/612 BC when Babylon took Assyria; Bab. fell in 539 BC ) => Horites or Hurrians => Hittites (current Anatolia) => Greece b) Sumeria => Canaanites => Minoan civilization and Greece.
For more information, read Zechariah Sitchin's "The Twelfth Planet."