It is quite clear from hundreds if not thousands of interviews given by people and also sightings that have been made that:
>several races of aliens are already visiting earth and some have possibly lived here occasionally long ago and humans are likely related to some of them.>They see us as too primitiv so they dont want to show themselves but secret treaties (Eisenhower meeting them 1954) have likely already been done behind the scenes long ago.Science fiction shows like Star Trek, Stargate, X-Files, movies, have all been inserted with small hints of extraterrestrials so people would mentally open up to the possible idea we are not alone.
To go a step further:
Even Astronaut Al Worden said on tv:
>humans are the aliens>we came with space ships here>weve forgotten it(This possibility does not exclude other space faring folks are visiting us too)
Link:
https://m.youtube.com/watch?v=yP05nhB2WLU&t=4m23s 