The ecology of religious beliefs

Although ecological forces are known to shape the expression of sociality across a broad range of biological taxa, their role in shaping human behavior is currently disputed. Both comparative and experimental evidence indicate that beliefs in moralizing high gods promote cooperation among humans, a behavioral attribute known to correlate with environmental harshness in nonhuman animals. Here we combine fine-grained bioclimatic data with the latest statistical tools from ecology and the social sciences to evaluate the potential effects of environmental forces, language history, and culture on the global distribution of belief in moralizing high gods (n = 583 societies). After simultaneously accounting for potential nonindependence among societies because of shared ancestry and cultural diffusion, we find that these beliefs are more prevalent among societies that inhabit poorer environments and are more prone to ecological duress. In addition, we find that these beliefs are more likely in politically complex societies that recognize rights to movable property. Overall, our multimodel inference approach predicts the global distribution of beliefs in moralizing high gods with an accuracy of 91%, and estimates the relative importance of different potential mechanisms by which this spatial pattern may have arisen. The emerging picture is neither one of pure cultural transmission nor of simple ecological determinism, but rather a complex mixture of social, cultural, and environmental influences. Our methods and findings provide a blueprint for how the increasing wealth of ecological, linguistic, and historical data can be leveraged to understand the forces that have shaped the behavior of our own species.Ecological uncertainty has long been implicated in the expression of cooperation and conflict in animal societies (1). For example, climatic variation predicts the incidence and distribution of cooperative breeding in birds (2, 3), and ecological uncertainty is associated with group living in mammals (4). These findings suggest that ecological duress can promote sociality when the benefits of cooperating during difficult periods outweigh the potential costs during benign ones (3). Although similar ecological pressures are likely to act upon humans (5, 6), the extent to which they have shaped the development of our own sociality remains disputed and is currently unclear (7–9).Human behavior is often mediated by socially transmitted conventions—that is, cultural norms—that govern expectations and behaviors during social interactions (10, 11). In particular, religious beliefs are thought to be a powerful mechanism for the enforcement of social rules (12–15). In support of these ideas, comparative studies have shown that a belief in moralizing high gods—defined as supernatural beings believed to have created or govern all reality, intervene in human affairs, and enforce or support human morality (7)—tends to be more prevalent among societies that recognize rights to movable property (9, 16), as well as in those that exhibit higher levels of political complexity (17), subsistence productivity (17), and norm compliance (18). In addition, psychological experiments have found that moralizing high god concepts can reduce levels of cheating (14) and increase willingness to be fair (19) and to cooperate (13). Such findings have provoked speculation that the prominence of moralizing gods at the level of cultures is a better predictor of cooperation in humans than individual religious beliefs (20). However, debates persist because statistical models assessing historical and regional dependencies are rare (e.g., refs. 7 and 9), and those that exist are limited in scope (21).It has long been theorized that the global distribution of religious beliefs may be shaped by ecological factors (7–9). Recent empirical findings indicate that beliefs in moralizing high gods not only intensify (22–27), but also promote cooperation (28–33) in situations of increased environmental risk. In addition, these findings indicate that ecological threats can strengthen mechanisms of norm enforcement in human groups (34). Given the strong correlation between cooperation and ecological uncertainty in nonhuman animals (2, 3), these findings are especially suggestive of a link between ecology and religion. In particular, the similarity between the global distribution of belief in moralizing high gods (Fig. 1), and that of social cooperation in birds (see figure 1A in ref. 2), raises the possibility that the distribution of this type of religious belief might also be shaped by ecological factors. Nevertheless, the evidence for an association between religion and ecology is currently mixed. For example, prior studies have indicated that resource scarcity is both positively (8, 9) and negatively (7) associated with a belief in moralizing high gods. These apparently contradictory findings may be the product of methodological issues. Specifically, some of the studies involved (7, 8) failed to account for the nonindependence of societies as a result of spatial proximity and common ancestry Galton’s problem (35)], whereas others were based on a relatively small sample of cultures (9) that may have been unduly influenced by a few preclassical cultures (21). In addition, all of these studies used extremely coarse metrics of ecology e.g., subjective ratings of resource abundance in (7, 8), or indirect measures of agricultural potential in (9)] that could have led to a distorted view of the role of environmental factors in shaping the spatial variation of religious beliefs.Open in a separate windowFig. 1.Global distribution of societies that exhibit beliefs in moralizing high gods (blue) or not (i.e., atheism or beliefs in nonmoralizing deities or spirits in red). The underlying map depicts the mean values of net primary productivity (i.e., the net balance of monthly consumption relative to production of carbon dioxide by living plants) in gray scale. Darker localities reflect places with greater potential for overall plant growth.To rigorously test for an association between ecology and beliefs in moralizing high gods, we systematically modeled the effects of basic environmental variables while accounting for the effects of known covariates of religious beliefs and simultaneously adjusting for potential dependencies related to shared cultural ancestry—as measured by patterns of shared language origin (35)—and spatial diffusion—as measured by the effects of cultural traits in neighboring groups (Methods). We consider the following covariates in our models, all positively correlated with a belief in moralizing high gods: political complexity (17), practice of agriculture (17), and recognition of rights to movable property, as measured by the practice of animal husbandry (9, 16). Our analysis is based on a global cross-cultural sample of 583 human societies (36, 37) that occupy a range of different habitats and are exposed to a wide array of environmental conditions (Fig. 1). Through a comprehensive characterization of key political and cultural variables, together with a rigorous treatment of key environmental factors, we offer a systematic test for whether the global distribution of belief in moralizing high gods is associated with underlying variation in ecological parameters.