We use interdisciplinary approaches to explain cultural diversity across time and space. We focus our efforts on both curating and enriching cross-cultural, global databases, and on using quantitative methods to explain broad scale cultural evolution.

Several of our projects have focused on testing big claims about our history. Chira et al. (2024) tested Jared Diamond's axis of orientation hypothesis. Using cultural, ecological, and linguistic data from over 1,000 mainland societies, we showed that ecological differences can hinder cultural diffusion. But contrary to Diamond's claims, our findings showed that Eurasia is no more ecologically homogeneous than other continental regions. Two studies tested the “drunk hypothesis”, which claims that the use of intoxicants has been essential for the rise and maintenance of large-scale, complex societies. Hrnčíř et al. (2025a) found a positive relationship between the presence of traditional alcoholic beverages and higher levels of political complexity in a global sample of 186 societies. However, the effect of alcohol was only modest after controlling for key confounders such as agriculture and environmental productivity. Hrnčíř et al. (2025b) examined the role of another intoxicant – kava made from the root of Piper methysticum – in 83 Oceanic-speaking societies. Although our analysis showed a positive relationship between traditional kava drinking and both political complexity and social stratification, the effect was not robust to control for spatial non-independence. Additionally, using a novel method of dynamic co-evolutionary models, we found no evidence for co-evolution between kava and sociopolitical traits. Chira et al. (2023) focused on our key relationship with domesticated dogs. We gathered data on the functions and treatment of dogs in 124 societies to show that closer dog-human relationships associate with dogs’ multifunctional use (hunting, guarding, herding etc.). We also show that that negative treatment and positive care are not mutually exclusive, indicating that the dog-human relationship involves a complex balance between offering care and minimizing costs.