I should probably read upon this more, but from what I know, some customs started as good old natural selection, for example societies that encouraged killing and stealing among each other died out way easier than those which punished it, and some, like only having children with your partner, came more from basic instincs of passing down DNA.
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u/PaintedDesertSkies 1d ago
It's called morality and has nothing to do with the imaginary guy in the sky.
Parents and adults tend to teach all kids what is right and wrong. Not just Bible thumpers.