Comets are, almost certainly, the main source of our water.
And while I'm not ruling out some sort of xeno-influence on our evolution, I think that the
Miller-Urey Experiment in the 50's pretty much proved life would have a tendency to generate under specific environmental circumstances.
Given that, I think it quite possible that nature can do the same in a broad range of situations that we've yet to experiment with to that degree.
I'm a believer that life started here, but then outside influences might have affected it along the way.
But then, who really knows?
