I have a theory that's pretty far out, but pretty much supports the OP. Now, before I get labeled a kook, let me just say that this is just one of
many far out ideas that my scope of vision enables me to consider. Some support others, many contradict each other, but few actually make their way
into my "belief system". I like speculation. Speculation is how we decide what concepts are worthy of trying to prove. And that's what we do here.
WHERE TO BEGIN?
I think it's possible (likely?) that "aliens" are either too far away to have physically made it to our planet in their own form -
or perhaps
they are interdimensional and have no physical form.
I think "Grays" and "Bigfoots" might be "avatars" (before you roll your eyes and groan - I've had this theory for over 10 years and have
mentioned it in posts on ATS since
way before the movie.) These "avatars" would be cloned mutants created from Earthbound DNA, and used as a
puppet workforce to carry out tasks in the "Earthly Realm"
This could explain why Grays resemble human fetuses. The human(oid) specimen is nurtured in an artificial womb and genetically enhanced until it
becomes a body capable of performing the tasks it needs to perform. The large head, in my theory, is to enable telepathic/telekinetic abilities, or
maybe they just need extra space for their advanced tickers.
So Bigfoots would be the other extreme: perhaps they have use for a vessel (I'm trying to avoid use of the word 'avatar') that is the most
physically powerful, rugged and strong they can get from human DNA - for something hands-on in our forests. Maybe he
is a boogieman; some kind
of guardian for an area. I'm not gonna try to second guess what extradimensional beings might be trying to do here.
The grays are said to move awkwardly, some say almost mechanically. Could it be that they are remotely controlled?
Of course Bigfoot moves gracefully. Maybe it's a trade-off? The big ugly hairy model is super tough, can climb trees and survive in the wild (and
only comes with one super-brain ability: invisibility). The tiny ugly gray one can house an entire cosmic alien consciousness, giving them all sorts
of sci-fi "powers" and is super-compact; but physically weak, and hard to maneuver?
I realize there's a chicken/egg conundrum in my theory, but that is easily poopooed by an elaborate explanation involving incubus/succubus, "demon"
possession and alchemy folklore that I'll save for another thread.
There are quite a few folks that link Sasquatch to UFOs and/or paranormal activity, and there are witness sightings of both in coinciding places. One
is a writer I've mentioned in a couple of BF threads named Jack Lapseritis. His book "The Psychic Sasquatch" might be interesting to you.