Alright. I see a large amount of arguments with this theory. So, I'll shed some light:
If you haven't noticed, amongst all earth based organisms, we are the most peculiar and adapted of all. But, there are also other organisms well on their way at looking like us, mostly apes. This could be because the highest point of evolutionary adaptation may be the humanoid type. It's pretty logical considering the complexity of four legged creatures such as koalas, elephants and chimps. Each one is more intelligent than the last and
the end point is in humans. so, be it as it is, It's only logical that the universal evolutionary chain always leads to humanoid life forms. Of course, everything depends on the planetary biosphere.
Changing the subject, there are theories that our evolution didn't take toll on it's own. Many now speculate that, perhaps, we were created by extraterrestrial entity's. This would explain part of the reason of why they are here and why they abduct us. Also, another more frightening theory is that they may consider us a food delicacy. After all, we eat other species on are planet, all of them being inferior to us. So, who's to say they don't eat us?
Finally, Some retired government officials stated that around the 1930's, a treaty was signed between earthlings and extraterrestrials, primarily the zeta reticulians (named by their
solar system). This was around the time when the Philadelphia project took place (the project was about developing invisibility or cloaking technology. Unfortunately, the first test went horribly wrong after the sea vessel it was tested on vanished with its crew, only to re-appear a few years later with most of its occupants either fused to the ship itself or gone mad). Maybe some of the unknown aircraft we see are secret
military projects.
for more info, go to this page:
http://www.bibliotecapleyades.net/vida_alien/alien_zetareticuli.htm#menu