Reply #59: Life certainly evolved many times on Earth. Odds are it's evolving in cans of soup right now.

[JackRiddler]

But soon as the poor little proto-critters that might form in that soup put themselves together, they are gobbled right up by the older critters who got their head start 4 billion years ago.

Anyway, if you remember hearing about the old Miller-Urey experiment from high school, it suggests that (especially given the timescales!) life probably started in many places on Earth before the first colonies of it spread around enough to run into each other (and eat each other) and it all started turning into a single biosphere.