To add to the discussion:
There are three qustions to the discussion:
1) Do humans naturally create/abide by morals?
2) How do humans "learn" morals/etc?
3) Are there are universal morals?
My personal definition relies on using society as a moral "base." i.e. everything is related to society; the entire purpose of morality is to
help society survive.
Consider society as an organism, and humans within society as cells in that organism (like people have cells - after all there's the rule that "all cells are composed of other cells"). The
only purpose of morality is to ensure that the society as a whole survives.
Thus, there are univeral morals across societies. Murder will
always be immoral because widespread murder damages the integrity of the society. So will
lying, cheating, stealing, and so on.
There will also be abstract morals that change with the times. How many wives is it moral for someone to have? - or somesuch.
Now, I think (as stated earlier) that people have an instinctive tendency towards morals; people will inherently "soak up" and/or invent morals.
The argument that individuals must have an incentive towards all morals is weak, because it's clear most people don't
know that actions in line with morality will benefit them greater than actions against morality. In fact, that's just outright false - immoral actions
can be better for the individual, even if they're worse for society.
It's also fairly irrelevent to argue that there's some moral compulsion or incentive making people moral
because that doesn't stand up.
People lie, cheat, steal, and so on all the time. Even though it's clearly against their morality.
It's also clear that, if morality is a tool society employs to ensure its survival, that
society will enforce morality.
There are only so many ways society can go this: execution, banishment, shunning, imprisonment, a fine, etc. In most of the US, the
only options are a fine or imprisonment; execution has been banned by most, shunning still occurs at the local level (neighborhoods and church groups), and banishment is frowned upon by our neighbors.
The severity of the punishment will correlate, approximately, to the severity of the offence. Thus, most people aren't punished (much) for lying, except in special circumstances; but murder is
heavily punished, as is rape and so on.
You can probably write a function expressing someone's liklihood of making a moral choice as the probability and severity of society punishing you, the gain by breaking the law, and the history of following moral codes.
So, my answers to the three questions:
1) Do humans naturally create/abide by morals? Yes.
2) How do humans "learn" morals/etc? Yes.
3) Are there are universal morals? Sort of (won't apply to an alien species. Consider slavery in this light).