" 7. The principle of reciprocal altruism—I’ll scratch your back if you’ll
scratch mine”—is universal; people do not by nature give generously
unless they receive something in return, even if what they receive is
social status.
8. The principle of moralistic punishment—I’ll punish you if you do not
scratch my back after I have scratched yours—is universal; people do
not long tolerate free riders who continually take but almost never give. "

― Michael Shermer , Brain, Belief, and Politics (Cato Unbound Book 92011)