We have proof. So far we already have detected a planet with Earth-like conditions (called Earth). Life formed on it. Possibly several times independantly.
The statistics for life on very earth-like planets are staggering.
But this line of thinking eventually leads to Fermi Paradox.
The apparent size and age of the universe suggest that many technologically advanced extraterrestrial civilizations ought to exist. However, this hypothesis seems inconsistent with the lack of observational evidence to support it.
> The statistics for life on very earth-like planets are staggering.
1/1. Sample size seems pretty shitty. Maybe if we find any other form of life in the galaxy OFF this planet, we might be able to bound the probability of it forming at all.
The apparent size and age of the universe suggest that many technologically advanced extraterrestrial civilizations ought to exist. However, this hypothesis seems inconsistent with the lack of observational evidence to support it.
http://en.wikipedia.org/wiki/Fermi_paradox