??? People have been fighting over land for as long as recorded history, and probably for longer. I might be misunderstanding your comment, because I don’t see how you can say that there were no conflicts over land ownership until the Reconquista. Or was the Roman Empire built through a series of peaceful agreements? And private land ownership absolutely existed. Ruling classes have held private estates for millennia. Again, please let me know if I’ve just completely missed your point.

This isn’t really true though. Although many IE langauges don’t use a descendant of *h₂r̥ktos for taboo reasons, plenty of languages do, e.g. French ours, Albanian ari, Greek άρκτος, Welsh arth etc.