i didn't say athos was an
independent society; i'm just talking about
culturally distinct societies, and which features do and do not seem to be universal across all of them. certainly nobody can doubt that the monks of mount athos have cultural traditions that strongly distinguish them from even other orthodox monks, much less nearby towns, but they still have their own rooms and robes. monks in the idiorrhythmic sketes can own quite a bit more than that, as i understand it, and in no case do monks steal personal property from visitors, as they would do if they rejected the concept of private property entirely
very few communities have not been "dependent on the outside from replenishment" within recorded history; even before recorded history, bronze-age mesopotamian kingdoms were evidently dependent on tin imported from cornwall, without which their rule would have collapsed
even deep into the stone age we have strong evidence of long-distance trading of prime knapping flint, but it's harder to know if communities were dependent on it; maybe if their trade routes were cut, they would have made do with lower-quality local flint
(just to disambiguate, this is not evidence that these ancient societies had private property; they might have been trading only their collective property. but they do seem to have made their tools of daily use from materials imported from other societies)
there are autarkic societies (the man of the hole, north sentinel island, the toromona, perhaps the himarimã, arguably north korea) but they are very much the exception, and have been for millennia, if not longer
i don't see that importing the young people that you need to perpetuate your society is particularly different from importing food or weapons. nobody doubts that argentina continued being a distinct society during the late 19th and early 20th century, despite mass immigration from europe increasing its population severalfold https://en.wikipedia.org/wiki/Immigration_to_Argentina#Featu...