I should say first of all that I do believe that somewhere out in the vast cosmos of the universe that intelligent life exists. Even ignoring such mathematical constructs as the Drake equation which make the likelihood of intelligent life in the cosmos so high that it is unreasonable to think otherwise, humans have only recently discovered that there are animals on Earth have a degree of self awareness that we assumed that only we as humans were capable of, so with the chance of having 2 or three self aware species on one planet makes that on another planet even higher. Also revealed recently is that amino acids have been found on comets (amino acids being one of the building blocks of life.)
Humans have basic structure built into their brains which gives them a habit of recognizing faces in random patterns. This is called pareidolia. For instance in this following picture (which is of a Nazi spacecraft) what looks to be a command console on the right side, always appears to me when I first look at it as a humanoid body with two eyes.
Of course on closer inspection it is not, but the human body still tends to find patterns for faces even when they are not really there (this is also represented in people finding a potato chip that looks like Jesus.)
Humans also have a somewhat egocentric viewpoint on the universe. For a long time we though we were at the center of the universe, but as we learn more and more about it we realize just how small our place in the universe is. I previously wrote that it is unrealistic to expect Superman to look like us in terms of his physiology and powers. What we do project on alien life forms is that if they are intelligent that they should basically be built like us. I am not an expert on aliens by any stretch though I have watched a few documentaries on some famous cases (, Kecksburg, , .) This all leaves me somewhat at a loss to explain what has occurred, as did the revelation last week of what some think to be a UFO crash site between Sweden and Finland.
One of the common links though is the concept that the aliens are greys, roughly humanoid with arms and legs and large bulbous heads. In terms of an actual encounter though would we expect aliens to look like anything else? This for me is one of the underlying themes of aliens in fiction. Granted the other self aware animals in the world are mostly all primates and therfore do look like us, but the dolphins do not fit in this group and in fact other than being mammals and having a common physiology, they look nothing like us. Space in fiction though is populated mostly with humans or human like people – Han Solo, Captain Picard or Flash Gordon (all of whom are incidentally also white.) Our projection of the universe starts inherently with ourselves but if we ever actually meet another intelligent life form will we even recognize it?