I think one of the reasons that humans are looking for other intelligent life is that we want to know whether or not there is the possibility that we too might not go extinct. So, for me the question is about the mortality of our species. We humans are obsessive about death and, in the Western World, the death of civilizations, aren't we?
I know that the Neanderthals didn't create a civilization, yet I also know that they were intelligent and that some of them had sex with humans. So, for a brief period of history, humans were in contact with and interacting with another intelligent life form. Why do we forget that?
I am going out on a limb here, which may be sawed off the proverbial tree. I have noticed that nature generally doesn't do things in singles; 'she' does things in twos or more. Why wouldn't 'she' have created more than one intelligent species, capable of creating a civilization, and why are people arguing that two civilizations existing in the same time period could be an impossibility?
I do have to ask, why did the Q (quelle, German for "source"), the 'writer' of the physical laws that govern this universe, make intergalactic, and even interuniversal, travel difficult, if not nigh improbable?