Contractarianism is the ethical model which I believe comes closest to describing the way the world really is. People are social animals - natural selection picks those who can co-operate with others, for the most part. Our brains have a natural impulse to "fit in". Of course, biology is messy and some of us are born with brains that do not desire to fit in, but most human beings try to form a "contract" with society. I do not kill you and you do not kill me, and that increases both our chances for happiness, reproduction and survival. You do not steal from me and I do not steal from you and at the end of the day, we both feel safer.
We find crime detestable, even if it does not happen to us, because if we didn't find crime detestable, society would not exist. The truly sociopathic tend to get themselves killed very quickly, thus, elminating their genes from the system. It's just the natural order of things. Now because neural development is a messy affair, and genes can recombine and get "shuffled", sociopaths occasionally arise and always will - but for the most part, human beings aren't like that. Nature has set us up to form social contracts with each other, because if we didn't.... WE WOULDN'T EXIST!
Contractarianism is basically a way to let individuals pursue their own selfish interests. Individually, no matter how strong, fast or smart we are, we can't get much done and our chances of survival are very slim. However, by creating a caring, orderly society, we increase our chances of survival greatly.
Truly co-operation is humanity's greatest power. Only by co-operating in large numbers can we achieve anything. Even Issac Newton, widely regarded as the most intelligent person who ever lived, said that he only got where he was by standing on the shoulders of giants.