“Shane the realist,” Shane retorted.  “Think of all the happy coincidences that went down when our universe was formed.  All these dangerously lucky sporadic events made life possible:  To start, you need a planet with water, and that eliminates like ninety nine point nine nine nine nine percent of all the planets in the universe.  After that you need a star that’s the perfect distance from the planet.  Too far and it freezes, to close and it fries.  Next you need a habitable atmosphere.  After that you need there to be some trace of life; an amoeba, a bacteria, some primordial ooze, whatever.  You need that life to evolve and survive for billions of years, until it grows into something intelligent.  You need this huge list of requirements, each requirement having a “one in a trillion” chance of occurring.  The more you think about it the more you realize how incredibly accidental life is.” 