Aliens - Are they out there? Have they visited us? And related questions

[thesummerqueen]

I heard an interview with an archaeologist who said he hears the arguments like that for Atlanteans and says "where is their garbage then?" That we just don't see anything in the archaeological record that can't be identified with one particular known historical group. If the aliens were here, either it was way before humans were around, or they were the neatest bastards to walk the face of the earth.