Do Aliens Exist?

I'm going with 'yes'.

First we said the world is the center of the universe, because the universe was designed for humans. After that, we said the world isn't the center of the universe, but the universe is still ours (at least certain religious folks might have felt this way). Then, scientists have told us that our existence could very well be a byproduct of randomness: as though the universe rolled a dice with billions of digits on it, one of them representing the right set of events to create 'us'. But after billions of dice rolls from the universe (nuclear fusion and fission and momentum from the big bang), we came into existence. I find it highly unlikely that, of all the spaces on those enormous dice, another roll hasn't generated the conditions necessary to bring about another species' existence elsewhere.

What fascinates me is the notion that it's a mere coincidence that we are carbon-based species, and it's a mere coincidence that we evolved to perceive within a certain frequency range (i.e. 10-10,000Hz for sound, whatever the range on the visual spectrum is, etc). There is a possibility that aliens simply could not communicate or recognize us (or vice-versa), if they exist and/or communicate within a frequency range we can not perceive.

My guess is that aliens have come to visit us, without our knowledge, and left, with a fantastic new case study of how not to exist as a civilization, and the way greed and numbness will catalyze any species' downturn and later, its demise.