The colonization of space, if it were ever to be accomplished, will be done in minuscule steps. Already we have a handful of people living for small segments of time in orbit around the earth. You won't be plucking people up from Earth and dropping them on Mars for the rest of their lives. Things will be done in short breaths, the moments away from home increasing over the generations.

What will the first outposts be built for? Scientific research. Assuming the perpetual progression of technology, one would assume that space travel would become faster, cheaper, and safer. People follow money wherever it leads, and as soon as it is reasonably economical, industries will follow.

The first (part time) denizens of space will be scientists, explorers, and industrialists (and thus workers). Of course the majority of people will choose to stay earthbound, but nevertheless there exists that minority who will not be confined. (And forget about shipping normal people offworld!)

Unfortunately, I sincerely doubt that we apes will ever get ourselves in order.