“Rather than reflecting an evolutionary outbreak of selflessness, studies of modern and recent hunter-gatherer societies suggest that they maintained equality not only through the institution of food sharing and reciprocal gift exchange, but also through what has been called ‘counter-dominance strategies.’ Sharing was what has been described as ‘vigilant sharing,’ with people watching to see that they got their fair share. The counter-dominance strategies through which these societies maintained their equality functioned almost as alliances of everyone against anyone whose behaviour threatened people’s sense of their own autonomy and equality. The suggestion is that these strategies may have developed as a generalized form of the kind of alliances which primatologists often describe being formed between two or three animals to enable them to gang up on and depose the dominant male. Observational studies of foraging societies suggest the counter-dominance strategies normally involve anything from teasing and ridicule to ostracism and violence, which are turned against anyone who tries to dominate others.”
— The Spirit Level, by R. Wilkinson and K. Pickett, 2011
“It has become evident the vigilant sharing, rather than automatic, unambivalent, totally altruistic sharing, is at the heart of the matter. This is the way people who carry the more altruistic traits protect themselves from those who are more disposed to act as free-riders. By manipulating behavior in the direction of conformity in matters of sharing and cooperation, moralistically aggressive group members not only reduce phenotypic variations at the within-group level, but do so strategically when it comes to selection possibilities for altruistic genes. They go out of their way to all but neutralize the potential advantage of those who strike them as being opportunistically exploitative, people who very likely carry free-riding genes.
I define such people broadly, to include camp bullies as well as freeloaders and cheaters. Bullying free-riders are taken care of by egalitarian sanctioning. Other free-riders take advantage of altruists by being lazy, by feigning injury, by selfishly wolfing down meat they have killed secretly, and so on. Such people are not necessarily bullies. Members of the band are sensitive to these deceptive opportunists too, and usually deal with them quite effectively.”
— Hierarchy in the Forest: the evolution of egalitarian behavior, by Christoper Boehm, 2001