I think I got it from a German Literature class. The professor had us read some formational texts, and one of them was a theory for the establishment of religion, written by some German 20th Century thinker. I can’t find the source now, but it was probably a pretty mainstream one, for all you internet sleuths out there.
He tried to put forward an evolutionary theory of religion. Basically, a tribe would come into conflict and children would kill their parents as a result. To try and prevent the same thing from happening to themselves, the children invented rituals that they taught to their children, so that they could control and direct their violence away from the parents. Instead of killing people, they would kill effigies made to look like people. Eventually, the children associate the effigies with their parents. But they like their parents, so they leave out the whole killing part when they teach it to their kids, who come to worship the effigies. They then kill animals instead of people. And so on. It was a really interesting exercise of rationalism!
If someone can find the source for me, I’ll give them my 2 internet points :)
Edit: I think it was Violence and the Sacred by Rene Girard.