Let us say you witness a little girl being brutalized in a dark alley. Something within you would cry out that that is wrong. You wouldn't deduce from premises that it is wrong. You would just feel it. An urge would well up inside you to do something about it, even if such action would considerably risk your life and limb. For example, you might feel a powerful urge to call for help, even though this might raise a small chance that the brutalizer would hear you and try to violently silence you. That urge is not rationally egoistic. Helping the little girl would not "serve you"; it would endanger you. Yet the urge to do so would be there, nonetheless. That is morality. What aspect of the brutalizer's assault would engender such a potentially self-sacrificing urge? It is not that in a society in which such violence is done with impunity, you yourself or someone who benefits you might end up being harmed. It is a primary urge that cries out, without any argumentative grounding, "it is wrong for him to do that to her body." That natural, internal moral imperative is what I call a property right: the inherent "ought" that lies with all of us regarding what, for example, a little girl can do with her body, and what other people can't.
Of course, property rights don't exist as ghostly connections between a human and an object. They are not "natural" in the sense that they are a material body or force. They are natural in that they are not artificial or customary. The same basic principle goes for property outside of one's body.
Were you to watch a sculptor, who saved up and bought his own materials, painstaking make a beautiful bust of an Olympian god over the course of several days, and then see another man come up, shove the sculptor aside, and run off with the bust, something inside you would say, "that was FUCKED up." You would feel a strong desire to see the bust returned to the sculptor. In that urge is implied the notion that the sculptor was the bust's rightful owner. Again, the property right resides within your psyche, as it would within most anyone who witnessed such an act.
SIDE NOTE: Now obviously these moral urges would not be as strong, if existent at all, within the brutalizer and the thief. They either ignore or sufficiently quiet those moral urges (in which case they are immoral, compared to the general tendency of mankind), are overwhelmed by countervailing passions (in which case they are disturbed, compared to the general tendency of mankind), or are pathologically devoid of empathy (in which case they are amoral and psychotic, compared to the general tendency of mankind).
All such instances (and any honest reflection on what one's own feelings would be in such situations) offer a surfeit of evidence of a moral code, written in our nature.