<p>Leadership, power, and prestige fundamentally structure human social worlds, and their emergence and developmental trajectories have attracted considerable archaeological discussion. To understand their antecedents and emergence, we develop and test a Social-Signaling Hypothesis that was originally advanced to explain conflict management in the small-scale societies that routinely attract archaeological attention. The hypothesis proposes that leadership, power, and prestige emerge from, and are acquired through, honest displays of individual and collective fighting strength. This proposition sidesteps critical flaws in current hypotheses concerning these developments, and it generates several novel predictions they are ill-equipped to explain. We begin by summarising and identifying the problems in current theorising. We then develop the Social-Signaling Hypothesis, before testing its predictions about leadership against an ethnographic database drawn from 151 of New Guinea’s small-scale societies. We find that the hypothesis accounts more parsimoniously for a wider range of data on leadership, power, and prestige than do prevailing hypotheses.</p>