To summarize the debate, there are effectively two sides. One side is convinced that human violence has decreased relative to population size throughout our existence. The supposed downward trend began in the days when we were all hunter-gatherers and continues into the present, when almost no one is a hunter-gatherer. In other words, this side thinks Hobbes was right about the nastiness, brutality, and brevity of human life before our self-domestication. Another side believes one of two things. Either we don't know how much violence there was among ancient hunter-gatherers, or there was less violence before we domesticated plants and animals, and became what a 19th century gentleman scholar might have called "civilized". Here's what I hope to convince you: Both sides are too confident in their ability to discern warfare from other causes of homicide in the archaeological record. That's very important because the debate about the nature of human violence often digresses into a debate about warfare, which is only one manifestation of violence. What about homicide? Suicide? Assault and battery?
Back to my conversation with Anstrosio and Badenoch. Anstrosio recently reviewed a new book called War, Peace, & Human Nature. It's not about war, peace, and human nature so much as it is about how much war and peace factor into human nature, and if indeed there even is a singular "human nature". Unfortunately, the book costs a ludicrous $85. Also unfortunate is that it's checked out of my university library until the 7th of July. Thankfully, Anstrosio put up PDFs of two the book's chapters, both written by Brian Ferguson, a critic of the Hobbesian point of view. I'll focus on one of these articles, called "Pinker's list: exaggerating prehistoric war mortality," the title of which is pretty self explanatory. Okay, maybe not.
So what is Pinker's list? In Better Angels, Steven Pinker put together two of the largest archaeological datasets on prehistoric homicide. The data spans multiple temporal, geographic, and cultural settings. One of the two datasets comes from Lawrence Keeley's War Before Civilization. Sam Bowles assembled the other for an article in Science magazine. From this data, Pinker calculated that the average death-from-war rate is 15%. (Ferguson didn't report the confidence intervals and I don't know if Pinker did, either, because all three copies of Better Angels are checked out of my university's library). Ferguson's goal in this chapter is show that, of the 21 cases in Pinker's list, six can be thrown out, and the rest are biased samples.
The strength of the book chapter is Ferguson's summary of the data sources for each of the 21 cases. He also makes a good verbal case that the data might be biased. But the chapter offers neither graph, table, nor parameter estimate to show how biased it might be, nor how certain we are in that bias. Ferguson also uses some weird logic to argue that some of the 21 cases should be thrown out. For example:
So let us look over Pinker's list. Of the original 21, Gobero, Nigher is out because it has no war deaths.
Three cases...are all eliminated because they only have one instance of violent death.