Alien Invasion, is it going on right under our noses?

Planets of the Solar System (Photo credit: Wikipedia)

For many years now, the question as to whether aliens even exist has been asked and overwhelmingly we see that the majority of those asked, believe this to be a given. Even those who have never had an experience of the third or fourth kind believe there is more than likely other worlds, and life forms in addition to man.
Skeptics often argue to the contrary stating any number of reasons why other planets, galaxies, etc could not support any life and so there is no logic behind the assumption other life exists. This however is because scientist, think like humans. We know humans have a set of criteria that must be met in order to sustain life. Our bodies have needs, as do all the occupants of earth that are specific to our planet. While no one person can say for certain life exists on any of the planets that we can actually look at in space and observe, planets beyond our reach, our knowledge may in fact have life that exists in conjunction to what that planet may generate. Perhaps alien life forms don't require the same amounts of oxygen, water, etc. that man does. Maybe their bodies and needs have adapted to their own planet. At any rate, the real question is, are they here, on earth right under our noses, existing among us? Many say yes. The next question is why?
Some theorize they are here to breed with humans in order to further their own race. They are here to hybridize their species to ensure their survival, and to perhaps make their bodies more readily able to live here on earth.
This plays into many theories out there stating they are here to "take over" this planet. In order to thrive here they must become a hybrid species able to tolerate our environment for long periods of time. To do this successfully means, to live amid humans, incognito.
Others believe that man is here as one large alien crafted experiment. A planet with a specific set of elements for life sustainability, in need of life forms that are capable of surviving not only harsh climate fluctuations, but other environmental threats. The evolutionary process brings  about a race of apex predators that manage to survive, much stronger intellectually with a little boost of technological help. However this life has to be created. Therein is the big issue at hand is this life created by God, or is it via alien intervention. Were aliens dabbling in hybridizing with apes first and thus man was created? What say you?