The following question has always bothered me: If superior intelligent Extra-Terrestrials do exist, why have they not contacted us ? Hence the following argument:
1. Earth exists in a protected zone. A guardian species from our dimension or perhaps another has placed Earth in the off-limits category away from all other Alien life. The reason for this is to protect humanity against interaction with other species that are more advanced and whose influence may prove to be deleterious to human kind.
2. Humanity may exist in this protected zone for the life time of our species but I suspect that is not the case. What I think is that when the ‘guardian’ species suspect that we are capable of weathering an interaction with a more advanced alien culture they will remove the barriers to allow contact to occur.
Its just a thought. But perhaps those UFOs so many have seen in the skies above are the guardian’s checking up on their protected species.