Poke has it exactly right. Thinking further along the lines suggested by his "social lubricant" idea, I'd suggest that fairness is no more than efficiency. Or, at the very least, if two prevailing doctrines of fairness exist, the more efficient doctrine will—ceteris paribus—in the long run prevail.

This leaves open the question of how closely to efficiency our notions of fairness have actually evolved, but that's an empirical question.