The Gaia Quarantine Breakout Hypothesis
The "Gaia hypothesis" contends that the Earth and nature is a type of conscious being, and is being damaged by the industrial actions of mankind: pollution, killing species, drilling, mining, bombings, etc.
Perkins proposed that one of the ways that the planet-- Gaia-- is trying to wake us humans up to environmental damage is by creating some sort of illusion in the minds of humans that there is an advanced ET civilization visiting us in UFOs. Consistent with this, there are many reports of people reporting alien visits where the aliens are warning us of what we are doing to the environmet.
Then Perkins proposed that the ultimate goal of Gaia is to get humans off the planet because of our destructive sociopathic tendencies and so creates these ETs/UFO illusions as an inspiration and motivation for mankind to go out to the stars and get off earth. So basically, planet earth/Gaia is creating a pretext for evil humans to escape the planet. It's a cool idea but obviously quite fantastical.
There is an older idea promoted by Anonymous Physicist, that there are evil ETs trapped here on earth that helped to create humans, and they are the main reason we are fucked up as a species. AP posited that these evil ETs were quarantined here by other ET races, to keep them from contaminating other planets in the universe and spoiling other emerging races of sentient beings. This is also a very interesting but rather fantastical idea.
There is basically no evidence for the Gaia hypothesis and honestly the evidence for AP's hypothesis is very weak. AP's theory on evil ET's trapped on earth has some decent explanatory power but has holes.
On the other hand, I think there is more evidence for some sort of ET quarantine around earth, to keep humans in check, than the above hypotheses.
As far as the Gaia theory, it's very cool and has some righteousness, but what I don't quite get it why people are so against the idea of ET's visiting the earth, given the vastness of the universe and the near certainty of highly advanced civilization out there that is capable of traveling here.