Costly Signaling as an Integral Part of the Systemic Approach to Religion

In this commentary on Purzycki and Sosis’ book Religion Evolving: Cultural, Cognitive, and Ecological Dynamics (2022), I subject their central assumption, namely that religious costs function as honest signals of commitment to systematic scrutiny. Many studies show that people who partake in (costlier) rituals cooperate (to a larger extent), but these studies are often non-experimental and say only a little about the causal relationship between signals and signaled quality, i.e., willingness to cooperate. Reviewing the existing literature on religious costly signaling, I argue that the core costly signaling model originally developed in evolutionary biology (and economics) is only partially supported when applied to religious signaling. At the same time, I show that little is known about the interactions between costly signals and supernatural beliefs. I discuss the results of the recent experimental work that tested basic assumptions of human costly signaling within the religious context.