The Secret Drivers Behind Europe’s Ancient Population Swings

A recent study by the Complexity Science Hub (CSH) suggests that the fear of conflict may have been as influential in shaping prehistoric European societies as the conflicts themselves.

Since the end of the last Ice Age, human population growth has been anything but steady, characterized by periods of rapid expansion interspersed with sharp declines. The reasons behind these fluctuations are still not fully understood. Previous research by CSH scientists Peter Turchin, Daniel Kondor, and an international team of collaborators suggested that social conflicts, rather than—or in addition to—environmental factors, may have played a significant role in these patterns. Now, they offer a new insight into this complex puzzle.

Wars and conflicts not only cause direct casualties but also create an atmosphere of distress and fear. This fear, by affecting where and how people settle, could have influenced substantially how the population in Europe developed, as shown in a study published in the Journal of the Royal Society Interface.

Flight And Overpopulation

“Globally, scientists have extensively studied and debated the presence and role of conflicts in prehistory. However, estimating their effects, such as those on population numbers is still difficult,” explains Daniel Kondor from CSH. “This is even more complicated by potential indirect effects, like people who, out of fear, leave their homes or avoid certain areas.”

These indirect impacts of conflict could have caused significant, long-term population fluctuations in non-state societies, such as in Neolithic Europe (circa 7,000 BC to 3,000 BC), according to the study’s findings. “Our model shows that fear of conflict led to population declines in potentially dangerous areas. As a result, people concentrated in safer locations, such as hilltops, where overpopulation could lead to higher mortality and lower fertility,” Kondor explains.

Match Archaeological Evidence

The ongoing threat would prevent the settlement of much of the remaining land. Co-author Detlef Gronenborn from the Leibniz Centre for Archaeology (LEIZA) in Mainz, Germany, adds: “The results from the simulation studies nicely match empirical evidence from archaeological fieldwork, like for instance the Late Neolithic site of Kapellenberg near Frankfurt, dating to around 3700 BCE. Like there, we have many instances of a temporal abandonment of open agricultural land, associated with a retreat of groups to well-defendable locations and considerable investments in large-scale defense systems like ramparts, palisades, and ditches.”

“This concentration of people in specific, often well-defended locations could have led to increasing wealth disparities and political structures that justified these differences,” adds Peter Turchin from CSH. “In that way, indirect effects of conflict might have also played a crucial role in the emergence of larger political units and the rise of early states.”

Complexity Science Meets Archaeology

To simulate population dynamics in Neolithic Europe, the researchers developed a computational model. To test the model, they utilized a database of archaeological sites, analyzing the number of radiocarbon age measurements from various locations and time periods, under the assumption that this reflects the scale of human activities, and thus, ultimately, population numbers. “This allows us to examine the typical amplitudes and timescales of population growth and decline across Europe,” Kondor explains. “Our goal was for our simulation to reflect these patterns.”

In the future, the model could help interpret archaeological evidence, such as signs of overpopulation or land use patterns, which in turn can provide necessary context and data for further refinements to modeling. This is a typical example of interdisciplinary collaboration that CSH aims to foster. “Using complexity science methods, we develop mathematical models to analyze the rise and fall of complex societies and identify common factors,” Turchin explains.

This involves collecting vast amounts of historical data, managed in specialized databases like the Seshat Global History Databank. “For the most complete picture possible, direct collaboration with archaeologists is immensely important. This study is a great example of the potential that such interdisciplinary collaboration can have,” Kondor emphasizes.

Reference: “Landscape of fear: indirect effects of conflict can account for large-scale population declines in non-state societies” by Dániel Kondor, James S. Bennett, Detlef Gronenborn and Peter Turchin, 1 August 2024, Journal of the Royal Society Interface.
DOI: 10.1098/rsif.2024.0210

The study was funded by the Austrian Research Promotion Agency.

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