“…Several mechanisms have been proposed to explain the phenomenon called parochial altruism-the fact that people are willing to fight for their social group despite the fitness costs. 6 The most important evolutionary explanations that have previously been proposed include kin selection, 7 group selection, 8 reciprocal selection, 9 altruistic punishment, 10 prestige, 11 sexual selection (women are attracted to brave warriors), 12 the opportunity of successful warriors to profit from the 4 Hastings and Shaffer (2008), Jugert and Duckitt (2009), Ladd (2007) 5 Fog (1997, Navarrete, Kurzban, Fessler and Kirkpatrick (2004), van Vugt (2006), Hastings and Shaffer (2008), Kessler and Cohrs (2008), Glowacki and von Rueden (2015) 6 Bowles and Gintis (2011), Nowak (2006) 7 Thayer (2004) 8 Crofoot and Wrangham (2010), Lehmann and Feldman (2008), Thayer (2004) 9 Tooby and Cosmides (1988, 2010) 10 Boyd, Gintis, Bowles and Richerson (2003) 11 Glowacki and Wrangham (2013) 10 Warlike and Peaceful Societies spoils and to mate with captured women from the losing group, 13 and cultural group selection. 14 It is a common characteristic of these proposed mechanisms that the effects are relatively weak, and perhaps too weak to compensate for the extremely high fitness costs of fighting.…”