Ultimately every conception of rights is subjective, but property is generally recognized as that which we acquire through First Possession (a principle observed throughout the Animal Kingdom), and Homesteading (taking unclaimed natural resources and reconfiguring them into a more valuable resource).

First Possession at least has been shown in Game Theory simulations to lead to stable equilibriums, so it's not surprising that property rights are so widely observed. I think observance of the Homesteading principle naturally emerges from observance of the First Possession principle.

Where it gets fuzzy, in my opinion, is property rights over natural resources like land, which derive almost all of their value from their natural form, rather than the value done to them by their original appropriator.