Oh yeah, there's no doubt about it.
The Ancient Astronaut theory -- (AAT) is true. I usually like to start off with the question; How were the pyramids built? .. Even with all our modern knowledge and technology, we still don't know how they were built.
AAT say that earth has been visited by ETs and/or technologically superior humans in very ancient times and that these events have been recorded as encounters with "Gods", "Flying Chariots", "Wars of Worlds" in ancient mythologies, legends and religions.
AAT is not the same by every researcher. Zecharia Sitchin (originator of the theories surrounding the Sumerian Annunaki) for example believes we were not only visited by extraterrestrials but actually created by them. Others say we were only ocassionally visited by ETs throughout history.
The similarity of ancient accounts, mythologies, cults and religions from all around the world, all basically describing "Gods" that flew around, performed technical "miracles", created things, destroyed them, taught humans skills, etc. In AAT we propose that our ancestors were describing technological events they didnt have the right vocabulary for. So saying "flames came out of the flying serpent" could very well be the description of an aircraft...for example.
And besides all that, we also have evidence of a civilization on our very own Moon;