haxxiy on 06 July 2011
Hard to say for we may never have idea on how common life is. Studing a bit of abiogenesis, I'm of the opinion life is very, very rare indeed.
Based on my own crappy, almost completely unscientific estimates, I'd say five to eight solar systems in your Milky Way are currently harboring life, with humankind likely being the most technologically advanced of those.
Maybe something carried away by earthly dust could grow and even evolve in Mars or Titan, or one of the galilean moons. Would that count as alien life?
That being said, someone could point me good sci-fi based on mankind colonizing the galaxy only, with no or primitive alien life at most? Out from games, only Dead Space has something close to it.
