This was a interesting philosophical quandary once upon a time until we discovered that morality wasn't uniquely a human characteristic. A great many species apparently possess a sense of morality. In all likelihood the mental framework predates even the emergence of Hominids. That said the evidence is pretty clear morality is actually a natural phenomena, and as it is predominantly instinctual it is absolute.
While reasoning tells us why the trait persists. That isn't what governs the interaction. What governs our morality is our own biochemistry in the form of emotions. Altruistic behavior results in good feelings even if we didn't comprehend why what we did was good. Just as negative behavior will result in bad feelings. Even if there were no consequences for our acts. As odd as it seems the majority of people are law abiding, because they don't want to suffer the consequences inside their own heads. Rather then any real punishment they are unlikely to receive.
Obviously that doesn't mean that we cannot override these impulses and engage in selfish behavior, but outside of some serious mental derangement all of us have to contend with the instinct to do right rather then wrong. Even if you had no conceptualizing of a written or spoken language, and had no words to put to your thoughts. You would still engage in behaviors to ingratiate yourself with others, and would prefer to not engage in detrimental behavior.
Morality is a absolute, and it is perfectly natural. I would give food to someone that was starving just to see them smile. In the end morality doesn't come from society.







