Look into the works of Zecharia Sitchin if this topic interests you. He brings up some interesting points about man's evolution, such as the fact that he is almost wiped out several times by climatic and other changes and when he comes back, he is more highly developed instead of being set back. Sudden advances like pottery, the ability to cross breed plants and a 365 day calendar aren't easily explained and often the history of these inventions doesn't follow any discernable pattern of normal advancement. Sitchin also calls into question Gods from other cultures, dieties such as Ahura Mazda, who just happens to be a winged disc. This is very close to what an uneducated person might call a flying saucer. He has a whole series of books that cover this topic through several cultures. Great historical fuel for lots of sci-fi off-shoots S