Testing the effect of circumscription on the evolution of social complexity in the Valley of Oaxaca, Mexico, using agent-based models

The initial emergence of complex societies in the archaeological record has often been explained by cultural and environmental conditions. In this paper, we formally test whether the conditions of the highly circumscribed region of the Valley of Oaxaca in highland Mexico could have intensified the formation of social complexity. The Valley of Oaxaca shows some of the earliest evidence for territorial expansion and multiple levels of internal organisation, or social complexity, in Mesoamerica and is considered a classic example of the effects of environmental circumscription. We build on our previous abstract agent-based model (Williams and Mesoudi, 2024) by incorporating real-world archaeological and environmental data from the Valley of Oaxaca to explore social complexity formation and test the impact of factors for which there is little archaeological evidence. The model results suggest that the mountainous surroundings of the valley could have contributed to social complexity formation, if we assume warfare was present throughout the time periods. However, the model also suggests that observed differences in social complexity formation between the three subvalleys of the Valley of Oaxaca were unlikely to be due to differences in circumscribing conditions. The model highlights key forms of archaeological evidence that might confirm or reject the effect of geographical circumscription in the Valley of Oaxaca.