Perhaps you don’t have children? Most parents quickly realize empirically that nature is much stronger than nurture.
Indeed, it is a child’s nature to be selfish, mean, thieving, self-serving, and out of control.
“Nurture” has to train that “nature” out of them in order to have a civilized human being.
What? Do you want me to believe against all common sense and known science that genetics doesn't miraculously end at the neck up as has been asserted for the last 60 years?