P Turchin Seminars

SimulPast & CaSEs Seminars


Peter Turchin

Professor, Univesity of Connecticut

External Faculty, Complexity Science Hub Vienna


The Zigs and Zags of Inequality in Human Evolutionary History

Room 24.104. Building Mercè Rodoreda (Ciutadella Campus). Universitat Pompeu Fabra (UPF) Barcelona. Wednesday May 24th 2017 at 12.00.

Most historians have abandoned the search for general principles governing the evolution of human societies. A typical approach to studying why institutions (laws, rules, sanctions, customs, and norms) emerge, change, and disappear is to focus on explanations that are contingent on the specific historical circumstances in which such institutions evolve. However, although every society is unique in its own ways, this doesn’t preclude the possibility that common features are independently shared by multiple societies. In my presentation I will argue that it is possible to study both the diversity and commonalities in social arrangements found in the human past. To advance beyond purely theoretical debates and comparisons based on limited samples, my colleagues and I are building a massive repository of systematically collected, structured historical and archaeological data, Seshat: Global History Databank. Specifically, I will focus on the evolution of institutions that promote equality (or vice versa, inequality). Levels of inequality have changed dramatically during the past 10,000 years of human evolution: from egalitarian small-­‐scale societies of hunter-­‐gatherers to first hierarchical societies with great inequities in the distribution of power, status, and wealth. The Axial Age (c.800–200 BCE) introduced another notable transformation, starting a move towards greater egalitarianism that has been continuing to the present. I will describe how the Seshat project codes data on religion, norms and institutions, and other cultural characteristics of historical societies in a form that make them suitable for statistical analyses, and present preliminary results of testing different theories explaining the evolution of a particular equity institution with these data.


Explaining the Rise of Mega-Empires: A Model of Cultural Multilevel Selection

Residencia d'Investigadors, Hospital 64, CSIC Barcelona. Thursday May 25th 2017 at 16.00.

What are the social forces that hold together complex societies encompassing hundreds of millions of people? How did human ultrasociality – extensive cooperation among large numbers of unrelated individuals – evolve? The theory of cultural multilevel selection is a powerful theoretical framework for addressing these questions. I use this framework to investigate a major transition in human social evolution, from small-­‐scale egalitarian groups to large-­‐scale hierarchical societies such as states and empires. A key mathematical result in the theory is that large states should arise in regions where interpolity competition – warfare – is particularly intense, resulting in high probability of cultural trait extinction. To make these general ideas more concrete I describe a model for the evolution of large states during the Ancient and Medieval eras, motivated by the ideas of Ibn Khaldun. Ibn Khaldun primarily focused on the interaction between pastoralists and farmers in the Maghreb (Northern Africa), but I extend his theory to Afroeurasia as a whole. The 'mirror-empires' model proposes that antagonistic interactions between steppe pastoralists and settled agriculturalists result in an autocatalytic process, which pressures both pastoralist and farming polities to scale up in polity size and military power.