Work on Cooperation and Collective Action

Combining quantitative analysis with large historical datasets, Peter Turchin and collaborators study how complex societies evolve, why they periodically enter crisis, and why some recover while others undergo severe breakdown.

Eugénie Bastié revient sur Le Déclin des empires et les travaux de Peter Turchin sur la cohésion sociale, la concurrence entre élites et les cycles de désintégration, en les rapprochant de la situation française.

Éric-Michel Tosolini, libraire à Alès, présente Le Déclin des empires. Sa chronique revient sur la cohésion des groupes, l’asabiyya et le projet de Peter Turchin de soumettre les explications historiques à une démarche scientifique.

This article engages with Mark Moffett’s proposed definition of society, which emphasizes shared group identification over social interaction, and argues for a different, problem-driven approach to definition in evolutionary social science. Rather than treating definitions as primary, I situate them within the broader research agenda aimed at explaining the Great Holocene Transformation—the dramatic expansion of human societies in scale and complexity over the past 10,000 years. My central analytical focus is on cooperation: the capacity of individuals to coordinate actions toward collective goals despite incentives to free-ride. Accordingly, society is defined here as a collective of individuals engaged in sustained cooperation, with interest group proposed as a more flexible and analytically useful term. Within this framework, polities represent a key subtype of interest groups, characterized by their role as independent political units whose persistence depends on maintaining cooperative cohesion, particularly among elites. Other commonly cited features of societies—such as group identification, territoriality, and intergenerational continuity—are treated as secondary mechanisms that support cooperation rather than defining properties. Ultimately, I argue that flexible, operational definitions are most valuable at intermediate stages of scientific inquiry, where they facilitate the construction and empirical testing of theoretical models.

During the Holocene the scale and complexity of human societies increased dramatically. Generations of scholars have proposed different theories explaining this evolution, which range from functionalist explanations, focusing on the provision of public goods, to conflict theories, emphasizing the role of internal class struggle or external warfare.…

How do large-scale human societies maintain functional integration? Over the last 12,000 years, polities grew over six orders of magnitude in population, far exceeding the scale at which the interpersonal mechanisms that promote cooperation in small-scale societies can operate. Here we test the hypothesis that cooperation and functional integration in large-scale societies is promoted by social (and, specifically, institutional) complexity. We model large-scale societies as territorial social networks subject to energetic, cognitive, and competitive constraints. We demonstrate that agricultural intensification generates increasing population density, raising the per capita rate of social interaction beyond what small-scale mechanisms can sustain and requiring institutional rules to substitute for interpersonal knowledge. The model predicts that territory and social complexity scale with polity population with exponents of 5/6 and 1/6. Tests against data describing hundreds of polities spanning the Holocene support these predictions, providing quantitative evidence that social complexity is a central integrative mechanism enabling large-scale human cooperation.

MLS in Cultural Macroevolution

Science Proceeds by Paradigm Shifts

Cultural macroevolution (CME) is a subfield of cultural evolution that studies large-scale changes in the cultural traits of whole groups. A central question in CME is how and why characteristics of polities (such as chiefdoms, states, and empires) evolve over time. Multilevel selection, and especially its application to cultural evolution, provides a very useful theoretical framework for CME because many polity-level characteristics evolve under selection pressures that act in opposite directions at different levels of hierarchical organization. In this chapter I discuss the conceptual framework that multilevel selection provides for studying CME and summarize the main empirical results from my recent book (Turchin 2025). I conclude that major predictions of cultural multilevel selection theory enjoy substantial empirical support.

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…

Es ist umstritten, wie stark historische Ereignisse durch Klimaschwankungen mitbestimmt werden. Forschende sind einem Verständnis der Zusammenhänge nun näher gekommen. Forschende um Daniel Hoyer und Peter Turchin (Complexity Science Hub Vienna) sind der Entwirrung der komplexen Wechselbeziehungen nun einen Schritt näher gekommen: Sie haben alle…

The link between environmental disasters and societal collapse, explained. The Roman Empire fell more than 1,500 years ago, but its grip on the popular imagination is still strong, as evidenced by a recent trend on TikTok.…

An interplay of cultural, political, and economic factors decides the course and outcomes of a "changing climate" crisis, and not environmental forces alone, researchers say. Drawing lessons from history, "not every ecological shock or climatic anomaly leads to collapse" and "not every crisis involves a major environmental stressor", the researchers at…

Climate variability and natural hazards like floods and earthquakes can act as environmental shocks or socioecological stressors leading to instability and suffering throughout human history. Yet, societies experience a wide range of outcomes when facing such challenges: some suffer from social unrest, civil violence or complete collapse; others prove more resilient and maintain key social functions. We currently lack a clear, generally agreed-upon conceptual framework and evidentiary base to explore what causes these divergent outcomes. Here, we discuss efforts to develop such a framework through the Crisis Database (CrisisDB) programme. We illustrate that the impact of environmental stressors is mediated through extant cultural, political and economic structures that evolve over extended timescales (decades to centuries). These structures can generate high resilience to major shocks, facilitate positive adaptation, or, alternatively, undermine collective action and lead to unrest, violence and even societal collapse. By exposing the ways that different societies have reacted to crises over their lifetime, this framework can help identify the factors and complex social–ecological interactions that either bolster or undermine resilience to contemporary climate shocks.

Der Ansicht vieler Forscher oder politischer Analysten nach befinden wir uns in einer "Polykrise" aus Klimawandel, Naturkatastrophen, wirtschaftlicher Ungleichheit, politischer Lagerbildung, gewaltsamen Konflikten und mehr.…

Ob Klimawandel, wirtschaftliche Ungleichheit oder politische Lagerbildung - immer wieder ist zu hören, dass wir in Zeiten der Krisen leben. Forscherinnen und Forscher haben nun eine historische Datenbank ähnlicher Krisen aufgebaut, um nach Faktoren zu suchen, die beim Bewältigen der Situationen geholfen haben.…

It's no longer just about stopping, but how we can live with climate change. To figure this out, we must delve into our cultures, as highlighted in a special issue of The Royal Society. A study by the Complexity Science Hub points out how our history could help guide the way. Currently, we are grappling with a global crisis convergence.…

Kriege, Inflation, Klimaerwärmung etc.: Die Gegenwart ist geprägt von einer „Polykrise“. In der Geschichte hat es solche Mehrfachkrisen immer wieder gegeben. Eine neue Studie zeigt nun, welche Faktoren es einer Gesellschaft erlauben, solche Situationen zu meistern. Stabilität bringt demnach vor allem sozialer Zusammenhalt.