This one is huge. Here's my pitch. Human beings learn by imitation. We don't just learn information and skills (like dancing, talking, and cooking) through imitation, though; we also learn from sponging off of other people's desires.
Think of it this way. If your brother wants that piece of cake, you're probably going to want it, too, even if you have pretty much the same piece already on your plate, and even if you're full. You want it because he wants it. A fight to the death—or at least until you are sent to your rooms—ensues.
Violence is the inevitable outcome of this competition, because not everyone can get what they want. Violence can erupt between two individuals who want, say, the boyfriend or girlfriend; or it can erupt between two nations that both want that oil field. As long as we desire what others desire, there will be violence.
If these ideas float your boat, check out my book Deceit, Desire, and the Novel: Self and Other in Literary Structure—an oldie, but a goodie.
If mimetic desire gets on a roll, eventually everyone will start to want the same thing. And what happens when everyone wants the same thing? It isn't pretty: aggression, strife, hostility, bickering, war. How can this be stopped?
Well, what I've found is that people stop the violence with... more violence. Here's how it goes: all the people fighting with each other just need to agree on a common enemy. Once they can agree that they all hate that one person, voilà—they have a scapegoat. They get everyone to unite around their hatred for that one person, and this creates a cohesive community.
Once the scapegoat is brought to a bloody or otherwise bad end, you get peace. You know... for everyone but the scapegoat.
Once the community has picked out its scapegoat and re-unified, it enters what you might call the honeymoon phase—that period when everything seems peachy. During this phase, the scapegoat suddenly becomes sacred. Why? Because he/she/it led to peace—never mind that he/she/it had to be expelled from society or killed to bring about that peace.
This, I believe, is how religion got its start. Scapegoats became gods. Don't forget that a certain someone died on the cross and all that…
So forget all that Rousseau you've read. Humans didn't create culture by suddenly deciding to be rational creatures and living according to some agreement that violence was a bad call. That's so Enlightenment. Culture and civilization as we know it started with the scapegoating mechanism. Even a Neanderthal could figure that one out—and, in fact, did.
You probably already got this, but my idea of the scapegoating mechanism flies in the bearded face of theories presented by our beloved Freud, who said that culture and civilization started with the Oedipus Complex—you know, that whole murdering your father and marrying your mother thing. Freud thought that civilization came about to prevent that from happening, but I say it came about as a result of the scapegoating mechanism.