Your review of Steven Pinker’s The Better Angels of Our Nature: Why Violence Has Declined (New York: Viking, 2011) and Robert Muchembled’s A History of Violence: From the End of the Middle Ages to the Present (Cambridge: Polity, 2011) points out that people have become less violent than ever, but that the authors cannot agree as to why this is so (“Punchline,” October 8, 2011). I am afraid neither of them has a plausible position regarding the reasons for the decline of violence, either. Of course, the data would be hard to gather for the claim that sounds most plausible, which is that humans have gotten domesticated over the last five-thousand years or so. Civilization is about domestication of the many by a few. Kings needed manageable subjects, but they also needed capable defenders of their kingdoms. Paradoxically, it was their armies that channeled violence outwards while blunting it inwards. As an added benefit, domesticated humans could be persuaded to collaborate on many other things, such as agriculture and religion. But domestication goes only so far. Humans can go feral in a very short time, as witnessed by the colonization of America and Australia, for instance. At forty generations per thousand years, five-thousand years is not much to boast about.