In 1945, in the end of the World War II, Kenneth Arnold saw some UFOs above Mount Rainier, Washington, while he fled in his airplane. It was the birth of the modern UFO's phenomenology, but this is older tan anybody can imagine. Ancient cultures as the Mayans in Mexico and Sumeria in Mesotopamia made sculptures and all kind of hieroglyphs and depictions as a symbol of a possible contact with an alien civilization. How those tribes millennium ago would to build places as Chichen-Itza or Gizeh's Pyramids, with an extraordinary about night skies? What if the actual human race is the result of a hybridization between them and our ancestors?