Adam and Eve do original sin and are banished from the garden of Eden.
Adam and Eve then lived on a grassland and have kids named Cain and Abel. Cain is a farmer and Abel is a Shepard.
Because Adam and Eve sinned they have to show Cain and Abel how to sacrifice to god.
When Abel sacrifices he does it the right way, but Cain does not. So when Cain gets rejected he kills Abell.
When God asks Cain where his brother is he says I don’t know. So when God finds out he puts a mark on Cains forehead and makes him Roam the Earth for eternity.