I'm seeing this on the National Geographic Channel now, and remember reading about this in the past.

What do you think?

http://en.wikipedia.org/wiki/Ancient_astronaut_theory

http://en.wikipedia.org/wiki/Starchild_skull

Neato!!! I read about this in "Alien Agenda" by Jim Marrs(fantastic book, I highly recommend it(read it SWF!)). I think it's definitely possible that ETs visited the Earth in the past. They're are many old stories that might depict abductions or ET visitations and they occur in areas all over the world. This is like the widespread stories about dragons, not that I believe dragons existed, the myths were probably created because of dinosaur fossils they found.
Look at this: http://en.wikipedia.org/wiki/Antikythera_mechanism
"Technological artifacts of similar complexity did not reappear until a thousand years later." There's also the Baghdad batteries.
Technology from ETs perhaps? Edit: The conventional explanations for these artifacts is too compelling, I changed my opinion of them.

Yeah, there's not much concrete evidence(government interference?), but it's certainly a plausible theory.

You folks might find some of these (http://sacred-texts.com/ufo/index.htm) of interest.

The Vimaanika Shaastra (http://sacred-texts.com/ufo/vs/index.htm)

So then why haven't they come back?

arguably they have...remember those reported abductions, sightings, etc....

Neato!!! I read about this in "Alien Agenda" by Jim Marrs(fantastic book, I highly recommend it(read it SWF!))..

googling that book