It's plausible that something like social contracts run deep in our nature. Along with the “economic justice” they need. 

1. Christopher Boehm (Moral Origins) studied 50 hunter-gatherer cultures to conclude that ~250,000 years ago, our ancestors shifted from an “apelike ‘might is right’” hierarchy to more egalitarian social structures.

2. Survival had become a team sport. Chasing big game toward teammates was more productive than solo hunting. However those team-productivity gains needed workable “profit-sharing.”

3. Even with well-fed teammates, hunting needs luck (e.g., 4 percent success rate). Then, as now, the logic of social insurance solved such problems by sharing profits and risks. Cooperators thrived. As did teams with the best adapted and enforced profit-sharing rules.

4. Boehm says all surviving hunter-gatherers enforce law-like rules that minimize egoism, nepotism, and cronyism. They use rebukes, ridicule, shame, shunning, exile, and execution. E.g., meat is never distributed by the successful hunter, but by neutral stakeholders. And close male kin of the condemned perform executions (which avoids inter-family feuding).

5. “Counter-dominant coalitions” punish dominant alpha-male abuses — like hogging an unfair share of meat. Ultimately, repeatedly offending alpha males were eliminated (a sort of inverted eugenics). Resisting tyranny and injustice are universal traits in today’s hunter-gatherers. They likely run 10,000 generations deep in our prehistory.

6. Such punishment created powerful social-selection pressures. And self-control became the lowest-cost strategy for avoiding penalties. Our shame and guilt systems likely evolved as ways to internalize (~as second nature) our culture’s social rules (~social contracts).

7. We intuitively recognize what is considered punishable (feeling guilty = intracranial karma = self-punishment triggered by our system 1). Cultures configure shame and guilt system triggers differently. But rules balancing short-term selfish gain with longer-term or team interests are more evolutionarily (and logically) productive. Imagining evolved urges as hard to resist ignores that self-control (especially regarding social rules) has long been needed for our survival.

8. Our ancestors bred themselves for teamwork. They used intelligently directed artificial selection (“auto-domestication”) of good cooperators as mates. Bad cooperators were selected less often for the hugely costly and highly collaborative business of raising the most helpless of all offspring.

Justice was once considered “Zeus’ greatest gift.” Greatest or not, the arc of our evolution has long bent toward justice (of the fittest for team-survival variety). Don’t believe Boehm? His position expresses the logic of vehicular viability and needism. Those always apply: Damage not what you depend on.


Addendum: For a fuller description of Boehm's Moral Origins see this Wilson Quarterly review


Illustration by Julia Suits, The New Yorker Cartoonist & author of The Extraordinary Catalog of Peculiar Inventions.