Which points to either our uniqueness (1) or our not understanding their alien motivations (4). A few points I'll make for fun: 1. Life on Earth propagates as

Which points to either our uniqueness (1) or our not understanding their alien motivations (4). A few points I'll make for fun: 1. Life on Earth propagates as much as possible. It is only external factors (mostly resources, but also predation and other factors) which keep populations in check. This is likely a shared trait of all (successful) life in the universe. This doesn't preclude the possibility of a species moving beyond this trait* but it does suggest that either the trait fails at some point prior to stellar engineering or interstellar colonization or that all advanced civilizations move beyond it. 2. Even if spreading throughout the universe is not a species' goal, whatever their goals are will require energy. It is likely those goals will require greater and greater energies as our own goals have and will continue to do for the foreseeable future. The only way I see around this problem is novel physics which seem impossible in our current understanding of the universe. 3. At some point every species must leave their host star or perish. (However, if they find themselves around a red dwarf, they will have quite a bit of time - and will not have to have moved since the beginning of the universe. So it may be we are freaks because we are around a shorter-lived orange star.) But this is speculation at best. I'd rather speculate that they all created their own pocket universes that are ideally suited to their species and left the rest of us behind. :) *Although I would suggest that natural selection is an unlikely candidate for the development of such a trait. In my opinion, this would require directly modification of whatever passes for DNA in the species. Even enforced population controls would probably not be enough to contain a species.