In this paper, we provide the most up-to-date evidence available in various behavioral fields in support of the hypothesis that the emergence of bipedalism and cooperative breeding in the hominin line, together with environmental developments that made a diet of meat from large animals adaptive, as well as cultural innovation in the form of fire and cooking, created a niche for hominins in which there was a high return for coordinated, cooperative scavenging and hunting of largemammals. This was accompanied by an increasing use of wooden spears and lithic points as lethal hunting weapons that transformed human sociopolitical life. The combination of social interdependence and the availability of such weapons in early hominin society undermined the standard social dominance hierarchy of multi-male/multi-female primate groups. The successful sociopolitical structure that ultimately replaced the ancestral social dominance hierarchy was an egalitarian political system in which lethal weapons made possible group control of leaders, and group success depended on the ability of leaders to persuade and motivate, and of followers to contribute to a consensual decision process. The heightened social value of non-authoritarian leadership entailed enhanced biological fitness for such leadership traits as linguistic facility, ability to form and influence coalitions, and indeed for hypercognition in general. This egalitarian political systempersisted until cultural changes in the Holocene fostered the accumulation of material wealth, through which it became possible once again to sustain a social dominance hierarchy with strong authoritarian leaders.