From outer space, yes!
Think about it, we could send a satellite to collect space gas (use a collecting surface hospitable to such) and verify the theorem.
What if we are swimming in a vast ocean of life... the seeding theory expanded (not only comets but all of space teeming with space's most hardy voyagers, micro-organisms).
The question arises of course, if these clouds of space-colonizers are everywhere, they'd have to be proof that life generates life. Some succeed in leaving the womb and go forth on intra and intergalactic voyages settling wherever conditions permit. Ingenious, these primitives nonetheless carry that fundamental script or some variant qualifying it as self-replicating, even adaptive. Engaged with the materials on the new terras, these archeae begin to form mergers, colonies specializing in the collective. Each native soil plays a different theme, resulting in an infinity of scenarios and symphonies, filling the vast unknown skies with music.
If one moves the analysis back, the question poses itself... where did these spacefarers arise? As it may for no other reason than intuition be that the galactic core is older than the rim that speciation must have begun there. It is exactly as Sid Meier would have it in his imaginarium computer game, SPORE.