Humans are both the only species known to have a morality of fairness, and the only species in which the social hierarchy is headed by an alliance (a ‘reverse dominance hierarchy’). I present evidence in support of the argument by Boehm (1999, 2012) that these two features are causally linked. The reverse dominance hierarchy is detectable in the fossil record around 300,000 years ago with the origin of Homo sapiens. From then onwards, according to the execution hypothesis, an alliance of adult males held the power of life and death over all members of the social group, and they used this power to advance their interests. The result was an intense selective pressure against antisocial behaviour and in favour of prosociality, cooperation and conformity to group norms, whether the norms were beneficial for the group as a whole or merely for the male alliance. The execution hypothesis thus argues that group dynamics have operated for at least 12,000 generations to favour the evolution of moral emotions, many of which are designed to protect individuals from the threat of severe punishment or death at the hands of a dominant alliance of males.
