The notion that planetary spread will cause necessarily war is IMO hugely flawed because it ignores entirely the issue of logistics. People don’t make war just because they piss each other off—I mean, sometimes they do, but war also has to be at least practical. Logistics of interplanetary or, heavens forbid, interstellar war are beyond nightmarish, which is why space operas always come up with jump drives or wormholes or gates or some other kind of technoblabbery doohickey to make wars across galactic empires work much like wars on this little mudball we’re used to. Otherwise, the universe has a very very strong “live and let live” bias; plenty of real estate, plenty of buffer zones in between, and it’s almost always cheaper to go somewhere empty than to wrestle somewhere full from the hands of someone else, especially if you want the planet to stay intact and livable.
There are precedents on Earth too. The Roman Empire and early Qin were both very powerful, very large, and very expansionistic, separated by thousands of years of cultural and technological divergence. According to this theory, they should have been natural enemies who went to war almost immediately. And yet they didn’t, first and foremost because in between them was a lot of inhospitable land that neither side could economically cross without arriving to the other substantially weakened. And also because they were probably different enough that they didn’t really concern themselves with mutual annihilation on ideological basis—that’s more the province of the devil you know, the heretic, the guy who’s similar enough that you care but different enough that he pisses you off. You don’t fight a Thirty Years’ War with some distant off culture that believes completely different things, you fight it with your brothers and sisters who dared believing a slightly different version of what you believe (and then, hopefully, you learn not to fight it at all because it’s really self-destructive and stupid).
Obviously there are risks—it’s true that space colonies would diverge from Earth for sure, and it’s true that having humanity spread on multiple planets would make the use of even potentially planet-ending weapons like nukes or relativistic kinetic bombardment a bit less taboo. That’s a problem, but it does not mean that History in such a future would be more predetermined than it ever has been.
The notion that planetary spread will cause necessarily war is IMO hugely flawed because it ignores entirely the issue of logistics. People don’t make war just because they piss each other off—I mean, sometimes they do, but war also has to be at least practical. Logistics of interplanetary or, heavens forbid, interstellar war are beyond nightmarish, which is why space operas always come up with jump drives or wormholes or gates or some other kind of technoblabbery doohickey to make wars across galactic empires work much like wars on this little mudball we’re used to. Otherwise, the universe has a very very strong “live and let live” bias; plenty of real estate, plenty of buffer zones in between, and it’s almost always cheaper to go somewhere empty than to wrestle somewhere full from the hands of someone else, especially if you want the planet to stay intact and livable.
There are precedents on Earth too. The Roman Empire and early Qin were both very powerful, very large, and very expansionistic, separated by thousands of years of cultural and technological divergence. According to this theory, they should have been natural enemies who went to war almost immediately. And yet they didn’t, first and foremost because in between them was a lot of inhospitable land that neither side could economically cross without arriving to the other substantially weakened. And also because they were probably different enough that they didn’t really concern themselves with mutual annihilation on ideological basis—that’s more the province of the devil you know, the heretic, the guy who’s similar enough that you care but different enough that he pisses you off. You don’t fight a Thirty Years’ War with some distant off culture that believes completely different things, you fight it with your brothers and sisters who dared believing a slightly different version of what you believe (and then, hopefully, you learn not to fight it at all because it’s really self-destructive and stupid).
Obviously there are risks—it’s true that space colonies would diverge from Earth for sure, and it’s true that having humanity spread on multiple planets would make the use of even potentially planet-ending weapons like nukes or relativistic kinetic bombardment a bit less taboo. That’s a problem, but it does not mean that History in such a future would be more predetermined than it ever has been.