Are people in big, modern societies more or less violent than our forebears? The answer is neither, according to a controversial new study: People who lived in small bands in the past had no more proclivity toward violence than we do today. The finding—based on estimates of war casualties throughout history—undercuts the popular argument that humans have become a more peaceful species over time, thanks to advances in technology and governance. But some critics aren’t convinced.
That includes the man who most recently popularized the idea, psychologist Steven Pinker of Harvard University, who calls the new findings “a statistical gimmick.” He argues in his 2011 book The Better Angels of Our Nature: Why Violence Has Declined that the emergence of institutions like nation-states with strong central governments, trade networks,
and wide-ranging communication increased interdependence and reduced deaths due to violence. He cited data suggesting that fewer people die in wars today, relative to a society’s total population, than among small tribes of hunter-gatherers, pastoralists, and horticulturalists—how human society organized for most of its history.
But a team led by anthropologist Rahul Oka at the University of Notre Dame in Indiana wondered whether there was a mathematical explanation for why fewer people proportionally are lost to violence nowadays. They reasoned that as populations get bigger, their armies don’t necessarily grow at the same rate. In a small group of 100 adults, for example,
it would be perfectly reasonable to have 25 warriors, says anthropologist and study co-author Mark Golitko, also at Notre Dame. But in a population of 100 million, supporting and coordinating an army of 25 million soldiers is logistically impossible, to say nothing of such an army’s effectiveness. Researchers call that incongruity a scaling effect.
The scientists dug through dusty tomes and digital archives to put together a list of 295 societies and 430 battles, large and small, dating from 2500 B.C.E. to today. They plotted two data sets: one comparing overall population size and the size of that society’s fighting force, and another comparing army size and casualty rate.
