roup violence Proceedings of the National Academy of Sciences of the United States of America, 102(43), 15294-15298; Roscoe, P. (2007). Intelligence, Coalitional Killing, and the Antecedents of War. American Anthropologist, 109(3), 485-495; Sussman, R.W. 1999. The myth of man the hunter, man the killer and the evoluti