The idea that life on Earth happened from inorganic sources is
absolute dogma, without a shread of proof, or even any decent
theories.
Exogenesis is, in my opinion, much more likely, but it's rarely
mentioned because of fear of getting too close to "Creationism." There
are directions in which most scientists don't allow themselves to
look. I know circuit designers like that.
The real tiebreaker, aside from some SETI type of discovery, must lie
in our DNA itself. "Junk DNA" was dismissed as useless artifacts of
evolution, but are likely to be a lot more important than anyone cared
to consider.
http://www.foxnews.com/story/0,2933,435184,00.html
http://features.csmonitor.com/innovation/2008/10/20/how-many-civilizations-are-in-our-galaxy/