I like Fil's response so I'm not going to rehash something that was already said because I agree with it. I just want to point out a few things that are specific with morality.
If you are alone on a island, morality is totally and completely irrelevant. Morality is only necessary in a group setting, even if that group has only two people.
The other thing about morality is that it is not set in stone and it can be fine tuned. There is no clear cut natural tendency to know what is morally right or wrong, despite some trying to argue that we do have this innate knowledge.
We have to be taught it. And when some people are not properly taught they tend to over step what is morally acceptable behavior.
What is accepted today as being morally right, may in fact in the future change to being morally unacceptable. It is because we decide as a group, a society what is acceptable and debate it. Often times morality has gray areas that are not clear cut. This is why it can take a long time before something changes.