[greggarious]

Did they get a head start though? All these atoms bouncing around started with the big bang after all :)

One theory I'm fond of is that we are not alone, but life is so rare that the distances between intelligent civilizations are too vast for us to ever observe them (or vice versa).

[PeterisP]

Many, many other planets had conditions suitable (as far as we understand what's suitable) for creating life when our planet didn't exist yet; out of all feasible planets we're younger than average, so others would have had a head start.