Violence is a pervasive theme in human society; it fills our news broadcasts, our movies, our novels, and, most especially, our histories. Why are people (mostly men) so prone to murder? Many anthropologists and even philosophers like Jean-Jacques Rousseau have chiefly blamed the corruptions of living in mass society. Not so, argues a new study, "The phylogenetic roots of human lethal violence," published in Nature by Spanish evolutionary biologists. They claim instead that natural selection has endowed us with our violent tendencies. The researchers' strategy is to survey intra-species violence in over 1,000 mammalian species in an effort to trace how violence arose. They also look at databases that compile rates of violence among human hunter-gatherer bands and ancient civilizations. While we are not the most violent species (meerkats are), we are pretty high up there on the list. From the study:
By compiling sources of mortality from a comprehensive sample of mammals, we assessed the percentage of deaths due to conspecifics and, using phylogenetic comparative tools, predicted this value for humans. The proportion of human deaths phylogenetically predicted to be caused by interpersonal violence stood at 2%. This value was similar to the one phylogenetically inferred for the evolutionary ancestor of primates and apes, indicating that a certain level of lethal violence arises owing to our position within the phylogeny of mammals. It was also similar to the percentage seen in prehistoric bands and tribes, indicating that we were as lethally violent then as common mammalian evolutionary history would predict.
ScienceAlert further reports…
…the team looked at our evolutionary history—usually, the closer two species are on the evolutionary tree, the more similar levels of inter-species murder they display. Based on that, Gómez predicted how violent humans should be, and then looked at causes of death in 600 humans population between 50,000 BC and today, to figure out how violent we actually are.
What they found was that, humans were around six times more murderous than the average mammal when we originated.
So, when our species first arose, around 2 percent of people (or one in 50) would have been murdered by other humans.
But that rate didn't stay the same—during Palaeolithic times, more than 10,000 years ago, the rate of lethal violence increased to around 3.9 percent.
Then, during the Medieval period, between 400 and 1400 AD, that rate rose to around 12 percent, before dropping over the last few centuries so that we're now far less violent than we were in our prehistoric past—most likely due to being more organised, and having stricter laws in place.
Not all mammals are violent, however. The study showed that around 40 percent of the 1,024 mammal species studied killed each other—and the primates were particularly bloodthirsty.
Interestingly, this study basically backs up the work reported by Harvard psychologist Steven Pinker in his insightful book, The Better Angels of Our Nature: Why Violence Has Declined. Pinker persuasively marshalls evidence showing that you are less likely to die a violent death today than at any other time in human history. When Pinker first proposed that violence has declined in modern times, he got a furious push-back from many intellectuals who are devoted to the idea that modern capitalism particularly incited people to murder. The authors of the new Nature study argue that the rise of modern social institutions have greatly reduced violence in contemporary societies. Their research basically vindicates Pinker's work.
Go here to read Reason's interview with Pinker and learn about the Capitalist Peace.