The Theory of Life

Life is theorized to be a very special affair. The spontaneous creation of life itself is either extremely rare or, in the case of humans, the only possible instance of life to ever be created.

If the creation of life is extremely rare, that would mean that humans will never find another alien. At best, some remains of an alien civilization will be discovered inevitably, but interaction with a living alien may never be possible. It could be possible that the few planets where life evolved beyond the single celled stage, it would be even more rare that they evolved into a space-faring civilization. In this case, they may even die out a couple thousand years later without ever meeting any other intelligent species due to the fact that civilizations would be so spread out.

On the other hand, if the only possible instance of life to ever be created was the human race, then that would mean that humans were created by something. This could have many different interpretations, from a classic Creationist theory of an almighty, knowing, God (or singular being of some sort) to being a controlled experiment by a group of some sort.

It could also be "what is old is new again" in that humans were once aliens themselves and "forgot" what they were and are rediscovering things long forgotten. Any possible alien ruins that could be found may actually be from ancient human civilizations.