Does animal sacrifice seem more of an idea from God, or by cavemen?

If we take the Abraham/Isaac episode (Genesis 22), I suppose that hypothetical cavemen, in their likely paganism, would have ignored God’s Providence and pushed through with the sacrifice of Isaac instead of accepting the ram caught in the twigs as a merciful substitute. After all if you, bright educated modern man, didn’t see God’s Mercy in animal sacrifices, how could cavemen ever figure it out ?