Our civilization has been driven by expansion. Without it we'd probably collapse into a neurally-connected well-organized ant colony without need for further technological/social/economic progress (which would naturally select/cull out corresponding features in our brain). And, i'd guess that is possible one of the forms of the Great Filter stopping many civilizations.
At 53 and good health, i'm contemplating that my end in 30-40 years would be me buying a one way to Mars and just exiting the habitat out without suit after enjoying a dinner with a Martian sunset view, breaking, even in such a small way, the chains of "We come from the earth, we return to the earth" :)