Another method could be frequencies... Like Radio Stations and such like the operate in different levels, may be there are beings as you mention around us right now, kind of like how we can see Bacteria but they can't see us.
It could be that like the Bacteria we have inside us we are just the Bacteria inside a larger creature...
All of this is possible... Yet not provable... And doesn't help us understand What made Man...
So what did make Man...?
The Big Bang happend long before any life appeared on our planet, but for some reason when we talk about the start of life we automatically see Earth as a starting point...
I don't wont to get to wrapped up in the Big Bang Theory, I am looking at the dawn of man around 4000 bc (If your a creationist or follow scripture of the bible) and 6 Million years ago if you follow Evolution.
I am looking at time that First Upright walking man came to pass with the brain capacity that we have now, the First Human.
You see I can't understand why Primates evolved in such away that they stepped out of Nature and started haversting Nature... Why would the Planet eventually help create a creature that would destroy the planet...?
Looking at some of Earths other creatures can also open up similar questions, but just focusing on Man alone shows shows SOME floors in the theory of Evolution being the SOLE catalyst.
I agree Evolution may help in subtle changes, like skin pigments, nose shape etc...
For me all the stories of Alien Sightings, Crashes & Abductions all add up to there being an external interest in us and us in them, especially in the last say 20 years, as technology becomes more advanced and camera's and video being on most persons new footage is coming into the public eye, yet most have been put across as fakes its hard to hold truth in them. But for some reason people hold more truth in an Archaic book (the Bible) or the opinion of One man (Charles Darwin)...
External Tampering with our gene pool for me is the only realistic theory...