nt critiques of the existing literature, see John Kekes’ The Roots of Evil (2007, Ithaca, Cornell University Press) * On lalling throughout history: Wrangham, R.W. & Glowacki, L. (in press). Intergroup aggression in chimpanzees and war in nomadic hunter-gatherers: evaluating the chimpanzee model. Human Nature; Bowles, S. (