Professor, I much enjoyed this post and found it very informative.
Proposition (1): The Simmel-Coser principle: conflict between groups tends to increase the internal cohesion and sense of group identity of said groups: G. Simmel, Conflict: The Web of Group-Affiliations, (Free Press, Glencoe, 1955); L. A. Coser, The Functions of Social Conflict, (Free Press, Glencoe, 1956).
Proposition (2): The Choi/Bowles hypothesis: the evolutionary benefits of parochial altruism:
“Altruism—benefiting fellow group members at a cost to oneself—and parochialism—hostility toward individuals not of one’s own ethnic, racial, or other group—are common human behaviors. The intersection of the two—which we term “parochial altruism”—is puzzling from an evolutionary perspective because altruistic or parochial behavior reduces one’s payoffs by comparison to what one would gain by eschewing these behaviors. But parochial altruism could have evolved if parochialism promoted intergroup hostilities and the combination of altruism and parochialism contributed to success in these conflicts. Our game-theoretic analysis and agent-based simulations show that under conditions likely to have been experienced by late Pleistocene and early Holocene humans, neither parochialism nor altruism would have been viable singly, but by promoting group conflict, they could have evolved jointly.” See; J-K. Choi and S. Bowles, “The Coevolution of Parochial Altruism and War,” Science, vol. 318, 2007, pp. 636-640.
Proposition (3): Thesis of warfare intensity: ethno-racial and cultural distance affects warfare intensity, with the greater the ethno-racial and cultural distance, the more intense the conflict: J. Solometo, “The Dimensions of War,” in E. N. Arkush and M. W. Allen (eds), The Archaeology of Warfare: Prehistories of Raiding and Conquest, (university Press of Florida, Gainesville, 2006), pp. 24-65.
Proposition (4): Universal genocide thesis: genocide is more frequent between ethno-racially and culturally dissimilar groups and may take the form of a “war of extermination”: P. Turchin, “Warfare and the Evolution of Social Complexity: A Multilevel Selection Approach,” Structure and Dynamics, vol. 4, 2011, pp. 1-37.
Conclusion: From propositions (1)-(4) expect the future to be one where the River Tiber, flowing down every street, will “foam with much blood”:
“History is littered with wars which everybody knew would never happen.” Enoch Powell (1912-1998)