The data from evolutionary psychology has now convinced me that we evolved a dual set of moral sentiments: within groups we tend to be pro-social and cooperative, but between groups we are tribal and xenophobic.
This is Iv-B and V-Bi in a Biv society, we can be cooperative in V-Bi or competitive in Iv-B. Civilization has grown as the I-O police and markets have evolved to moderate criminal behavior.
Archaeological evidence indicates that Paleolithic humans were anything but noble savages, and that civilization has gradually but ineluctably reduced the amount of within-group aggression and between group violence. And behavior genetics has erased the tabula rasa and replaced it with a highly constrained biological template upon which the environment can act.
I have thus changed my mind about this theory of human nature in its extreme form. Human nature is more evolutionarily determined, more cognitively irrational, and more morally complex than I thought.