What this reveals – and the reason why the first person God tells the man he should not have sex with is his father’s wife (perhaps his own mother, or perhaps – and more likely – another wife of his father who is not his mother) – is a social system in which the father was once the “tribal chieftain” who may have abused his power in that way, and God is telling the son, who has taken over the reins of power from his aging and weakened father, that he should not do as his own father did – let alone as the Canaanites before him had done.