I would think there would be two situations. One, where there was support from "home", Earth or some other well-equipped base, and two, if there were some colony floating around isolated from all but itself.

An isolated colony which had to count on finding a "dead" planet instantly capable of supporting life as we know it would seem to be a long, long shot.

Man's evolution has always been from the unique to the common. Just one example has been from regarding the Sun and Universe as revolving around the Earth to realizing the Earth revolves around the Sun, etc.

I think our belief that life may be unique to Earth is one of those things. And it will be proven wrong, there is life everywhere just as there are stars and galaxies everywhere.

And even if there were a dead planet suitable for life, would an isolated colony be able to bring enough viable organisms to support the rest of life as we know it? The stuff necessary to grow plants, for instance, all the little critters which function in ways to fix nitrogen?

Dunno. I think humanity would be one more energy consumer competing with a lot of others. And just because we've come out at the top of this food chain doesn't mean we'd fit into the top of another. Even one which wasn't technologically advanced.

Interesting questions, though. Thanks.

Arf