Nature, as we know, regards ultimately only fitness and not our happiness, and does not scruple to use hate, fear, punishment and even war alongside affection in ordering social groups and selecting among them, just as she uses pain as well as pleasure to get us to feed, water and protect our bodies and also in forging our social bonds.

Leonard Katz, ‘Toward Good and Evil’, in Evolutionary Origins of Morality: Cross-Disciplinary Perspectives, Thorverton, 2000, p. xv