Complexity science can help archaeologists understand how the everyday actions of ancient people accumulated into the large-scale patterns we excavate today.
In her new book, Thinking Through Archaeological Complexity, Santa Fe Institute External Professor Stefani Crabtree (Utah State University) shows how methods drawn from complex systems, such as agent-based modeling and network analysis, can reveal hidden details of the very human stories that ultimately led to the artifacts, buildings, and food remains unearthed in the present day.
“What I mean by complexity is the science of complex adaptive systems, where you can understand how the actions and interactions of individuals lead to larger overarching structures,” Crabtree says. “Archaeology is well suited to these tools because we usually see the end point — a whole building or midden — and have to infer the interactions that built it.”
Crabtree wrote the book as a practical guide for students and researchers who often know what tools exist but struggle with when and why to use them. While earlier volumes by other experts have addressed topics like network science or computational modeling in archaeology, they have typically taken a narrow lens. Crabtree integrates these approaches within a broader framework, linking theory, method, and case study to advance archaeological problem-solving.
“Stefani Crabtree has brought the best of SFI to archaeology, focusing a complexity lens on the human–environment nexus by bringing in insights from ecology, network science, and geography,” says SFI Science Board Fellow Simon Levin (Princeton University).
One of her case studies looks at the Ancestral Pueblo people in the American Southwest. Some archaeologists believed these societies had powerful leaders because burials contained exotic goods such as chocolate imported from Central America. Others emphasized the egalitarian traditions maintained by Pueblo descendants today. To test these ideas, Crabtree built an agent-based model where digital “households” follow simple rules about farming, family ties, and conflict over land. The model showed that, during favorable climate years, hierarchies could emerge. But when conditions became less predictable, those hierarchies dissolved.
“These simulations give us a way to explore competing ideas,” Crabtree says. “They don’t tell us what must have happened, but they let us test what could have happened and compare that against the archaeological record.”
A second case study reconstructs ancient food webs in the Four Corners region, using data from centuries of middens — trash heaps filled with bones, seeds, and other remains. Crabtree and colleagues cataloged what people ate, from maize and wild plants to deer and turkeys. Their analysis showed how maize reshaped the ecosystem: while it became a staple food, it also attracted pests and animals that competed for the crop. The picture that emerges is one of societies constantly adjusting to ecological pressures, an echo of the trade-offs communities in the region still navigate under climate stress today.
Even the book’s cover art reflects this theme. Crabtree painted it herself, layering a watercolor of Pueblo Bonito, a massive site at Chaco Canyon in New Mexico that once contained hundreds of rooms, with binary code that translates the title, a nod to both the archeological and computational lenses she combines.
"The environment, culture, and human cognition — the subject matter of archaeology — are the three most complicated systems of which we have tangible knowledge," says SFI External Professor Steve Lansing. "Stefani Crabtree offers a wonderfully readable introduction to complexity science as a way to think about the emergence of order in the archaeological record."
Ultimately, Crabtree argues that archaeology, when paired with complexity science, offers more than a retrospective account of human history. It becomes a laboratory for understanding adaptation.
“I hope readers come away curious and see archaeology’s value for today,” she says. “By moving beyond artifacts to the relationships that made them, we can carry lessons from the past into more sustainable futures.”
Thinking Through Archaeological Complexity (Routledge) is available for pre-order beginning October 10 and will ship after October 31, 2025.