Duration of agriculture and distance from the steppe predict the evolution of large-scale human societies in Afro-Eurasia

Why do the 99.9% of humanity live in large-scale societies organized as states? During the Holocene (the last 10,000 years), human societies have been transformed utterly: from small groups of nomadic foragers to our current interconnected world of large-scale societies organized as states. Population numbers, agricultural productivity, technological…

We organize ourselves into communities of hundreds of millions of individuals, inhabit every continent, and send people into space. Human beings are nature’s greatest team players. And the truly astounding thing is, we only started our steep climb to the top of the rankings—overtaking wasps, bees, termites and ants—in the last 10,000 years. Genetic…

What was history's biggest empire? Or the tallest building of the ancient world? What was the plumbing like in medieval Byzantium? The average wage in the Mughal Empire? Where did scientific writing first emerge? What was the bloodiest ever ritual human sacrifice? We are used to thinking about history in terms of stories. Yet we understand our own world…

In War and Peace and War, Peter Turchin uses his expertise in evolutionary biology to offer a bold new theory about the course of world history. Turchin argues that the key to the formation of an empire is a society’s capacity for collective action. He demonstrates that high levels of cooperation are found where people have to band together to fight off…

Multilevel selection is a powerful theoretical framework for understanding how complex hierarchical systems evolve by iteratively adding control levels. Here I apply this framework to a major transition in human social evolution, from small-scale egalitarian groups to large-scale hierarchical societies such as states and empires. A major mathematical result in multilevel selection, the Price equation, specifies the conditions concerning the structure of cultural variation and selective pressures that promote evolution of larger-scale societies. Specifically, large states should arise in regions where culturally very different people are in contact, and where interpolity competition – warfare – is particularly intense. For the period of human history from the Axial Age to the Age of Discovery (c.500 BCE–1500 CE), conditions particularly favorable for the rise of large empires obtained on steppe frontiers, contact regions between nomadic pastoralists and settled agriculturalists. An empirical investigation of warfare lethality, focusing on the fates of populations of conquered cities, indicates that genocide was an order of magnitude more frequent in steppe-frontier wars than in wars between culturally similar groups. An overall empirical test of the theory’s predictions shows that over ninety percent of largest historical empires arose in world regions classified as steppe frontiers.

One of the greatest puzzles of human evolutionary history concerns the how and why of the transition from small-scale, ‘simple’ societies to large-scale, hierarchically complex ones. This paper reviews theoretical approaches to resolving this puzzle. Our discussion integrates ideas and concepts from evolutionary biology, anthropology, and political science. The evolutionary framework of multilevel selection suggests that complex hierarchies can arise in response to selection imposed by intergroup conflict (warfare). The logical coherency of this theory has been investigated with mathematical models, and its predictions were tested empirically by constructing a database of the largest territorial states in the world (with the focus on the preindustrial era).