Cities are “social reactors,” concentrating people and accelerating interaction and social outputs – in essence, burning hotter and brighter as they get denser.

A recent working group at SFI, “Human Settlements and Networks in History,” furthered a long-term exploration of urban scaling theory as it applies to human settlements through history and across cultures.

The team – including SFI External Professor Scott Ortman, now at the University of Colorado Boulder, and SFI Professor Luís Bettencourt – recently published an article in the Journal of Archaeological Science that involves a case study of the Inka expansion in Peru, which occurred around 1450. They found that changes in settlement size distribution seem to predict the level of economic growth that occurred in the subsequent century, suggesting it might be possible to learn more about the factors that encourage economic development by paying attention to the distribution of population in settlements across a society.

A more recent paper in PLOS One showed than medieval and modern European cities share remarkably similar population density characteristics.

What is emerging, says Ortman, is an aware- ness that the framework initially developed to make sense of contemporary urban data may be very broadly generalizable to societies of the past. “If it’s true,” he says, “the archaeological record then provides a rich data source for elaborating and testing the theory, and the things we learn about scaling phenomena by studying the archaeological record should be directly relevant to the way contemporary societies work.”

Beyond this possible connection, Ortman thinks there is potential for archaeological research to contribute to a general theory of human societies as complex systems.

The SFI-inspired Social Reactors Project, now centered at Boulder, seeks the common properties of human settlements through time and space. More at