[krapp]

I think they're making reference to some ancient Alien theories along the lines of Erich Von Daniken and others, which tend to postulate that certain ancient and megalithic structures would have been impossible to build without modern technology, and thus can only have been the result of alien interference.

It's worth mentioning that there is often a white supremacist or pro-colonialist dimension to these theories. Rarely does anyone question whether the Greeks built their architecture, for instance, but according to these people it's simply not possible for the Egyptians to have built the pyramids.