Boehm says all surviving hunter-gatherers enforce law-like social rules to prevent excessive egoism, nepotism, and cronyism. They use rebukes, ridicule, shame, shunning, exile and execution (typically delegated to close male kin of the condemned, to avoid inter-family feuding). - http://blogs.scientificamerican.com/guest-blog/2013/05/29/justice-is-in-our-nature/