If you’re like more than 50 percent of the world population, you live in a city or an urban center. It’s a long road from the small tribal villages our ancestors first occupied. How did we get here? That’s a key question at the heart of anthropology. How could human groups have transitioned from small, initially nomadic tribes to agricultural settlements and eventually, to city-states and nations? In recent decades, social scientists have turned their attention to religion as a possible factor in the evolution of large-scale societies. They argue that religion provides certain ingredients to help create a stable society: group cohesion and large-scale cooperation. Indeed, research strongly suggests that a common belief in divine supervision and punishment by gods or other supernatural entities can strongly influence cooperation, even between distant strangers.Before the dawn of agriculture, humans lived in relatively small groups of extended families, constantly in pursuit of animal and material resources whose availability changed with the seasons. This caused intense, often violent competition for resources between unrelated tribes. Under these conditions, cooperation can be understood in terms of genetic relatedness, preference toward mates and reciprocity. Indeed, social scientists and evolutionary biologists have long noted that individuals instinctively behave in ways that improve the reproductive success of their relatives, mates and those with whom they frequently interact.The development of agriculture, however, resulted in a dramatic expansion of social complexity, leading to the emergence of large-scale societies. Consequently, social life was no longer based exclusively upon face-to-face interactions in small, egalitarian groups. The traditional models of cooperation break down at this scale, as individuals must frequently engage in one-off transactions with anonymous strangers. This ‘problem of cooperation’ concerns how human groups could have stably made the transition from small nomadic groups to large-scale societies.One increasingly popular hypothesis contends that commitment to the same morally concerned gods fosters cooperation between individuals of the same faith (referred to as co-religionists) where supervision may otherwise be absent. That is, people may be more likely to cooperate within large groups if they believe that omniscient gods monitor behavior and punish moral transgressors. Moralistic gods may act as societal glue, promoting impartiality between distant strangers who share a common conception of god. The competitive advantage depends upon the intuitive fact that groups composed of cooperative individuals outcompete groups composed of uncooperative individuals.Research by Azim F. Shariff and Ara Norenzayan suggests that social circles, and thus societies, expanded as the perceived ability of gods to monitor and punish behavior increased. Belief in supernatural moral arbiters produced the same kinds of concerns, though often amplified, that individuals might feel today when being monitored by members of their community. They fear punishment, condemnation and a damaged reputation. These ever-present punitive deities, therefore, allow for a larger number of stable interactions between people who may otherwise not be motivated to cooperate, thus pushing the outward the bounds of society. In this way, societies have grown complex under the watchful eyes of increasingly powerful deities. Owing in part to their ability to monitor and punish behavior, certain gods were culturally maintained and spread over large geographic areas. These gods conferred powerful group-level benefits during intergroup competition and eventually came to reign over the major world religions of today.To investigate these claims empirically, researchers typically (1) conduct cross-cultural studies on diverse groups of people and (2) determine individual ideas about god, such as what god cares about and what types of behaviors are punishable. The first consideration allows researchers to focus not just on large, often Western and Christian societies, but small societies as well, which are crucial for understanding the expansion of prosociality. The second consideration encourages precise measurements of individual conceptions of god, which are then tested in behavioral experiments. To better understand this process, consider the following experiment, an account of which was recently published in Nature by Benjamin Grant Purzycki at the University of British Columbia and a team of researchers from across the globe.Addressing the transition from small groups to large societies, Purzycki’s team asked whether individuals from diverse populations across the globe who adhere to moralistic gods are more likely to behave impartially toward anonymous co-religionists with respect to themselves and their neighbors than those who do not adhere to moralistic gods. In other words, how strong is the societal glue provided by big gods as it spreads across large societies? Is it strong enough to sustain cooperative behavior across great distances? Do geographically distant co-religionists behave toward one another as they would toward their neighbors? If yes, big gods may have played a significant role in the growth of modern societies.To measure prosociality toward anonymous co-religionists, participants were asked to play a game, ‘in private [involving] 30 coins, two cups and a fair die with three sides of one colour and three sides of another colour.’ Each participant was tasked with allocating the coins, one at a time, into one cup or the other. Allocation was determined by the participant first mentally choosing a cup, and then rolling the die. If one color came up, the player was instructed to allocate the coin to the cup she chose; if the other color came up, the player was instructed to allocate the coin to the opposite cup. Since cup selection occurs mentally, participants could cheat by overriding the random outcome of the die in favor of the cup they chose. In a fair game, one would expect the coin allocation to finish at around 15 coins per cup. Each participant played this game twice. In the first game, there was a cup for a local co-religionist and a cup for a geographically distant co-religionist; in the second, the cup for the local co-religionist was replaced with a cup for oneself.In preliminary interviews, the researchers assessed the participants’ views on their personal god’s involvement in moral issues. The cross-cultural sample included many different local gods and big gods with varying degrees of knowledge and powers to punish unfairness. The researchers found that participants who were unsure about whether or not god punishes people put significantly fewer coins in the cup for the distant co-religionist than participants who were sure that god punishes. That is, individuals who believe in morally concerned gods are more likely to behave impartially toward distant co-religionists relative to both their local community and themselves than those who do not. These findings support the hypothesis that moralistic gods foster cooperation between anonymous co-religionists in the absence of other incentives for fair behavior (e.g. genetic relatedness or reciprocity). Consequently, punitive gods may have contributed to the expansion of prosociality and thus the development of large-scale societies.But what, precisely, do we mean by ‘large-scale’ societies? Large-scale societies are societies which have complex economies and some form of industry and intensive agriculture. These societies are organized hierarchically, both in government and industry. They have a division of labor where separate regulatory organizations deal with agriculture, bureaucracy or defense. Moreover, each division is in some way concerned with the acquisition, management or protection of resources. Competition for resources and the drive for regional dominance often led to warfare in early societies, and warfare would in turn demand technological innovation and an expanded labor force. Effectively dividing labor would have given certain groups a competitive advantage over others. For example, if a tribe settled down to protect certain resources, or indeed to manipulate production by saving seeds and domesticating animals, that tribe would have a steadier supply of food. Consequently, its population would expand, labor divisions would become more specialized and cooperation between strangers would become essential. Widespread belief in moralistic gods would then confer a significant advantage to groups as a means for solving new and urgent social problems. The successful settlements eventually gave rise to modern city-states and nations; the beliefs in deities that conferred the greatest cultural advantages were maintained and gave rise to modern religions.As for Purzycki’s findings, they build upon previous work and offer interesting insight into the evolution of wide-ranging prosocial behavior between strangers. It is fair to warn however, that the results merely establish a correlation, albeit a strong and telling one, between belief in a certain kind of god and impartial behavior. Thus, such findings are best taken in support of further empirical evidence. Indeed, the factors which led to the development of large-scale societies were manifold, but belief in gods may have played a key role.But, is this the whole story? What about your city? What about today? Interestingly, research by Carlos A. Botero of Washington University in St. Louis suggests that contemporary societies become less religious the better off they are, economically, politically, and environmentally. The more volatile the political climate and the more dangerous the environment – ultimately, the greater duress a population is under – the more likely that a population is to believe in moralizing gods. Why would gods play a more central role in both early societies and volatile contemporary societies? It could be that many early societies were quite volatile. Once a population becomes stable, with plentiful resources and strong defense, there is less need for constant supervision and the looming threat of divine punishment. Indeed, people may be less likely to cheat a system if they are benefitting from it.As Purzycki and his team conclude, ‘when people are more inclined to behave impartially towards others, they are more likely to share beliefs and behaviours that foster the development of large-scale cooperative institutions, trade, markets and alliances with strangers.’ Perhaps this is the essential wisdom of the study. Then, we must ask, how else can we promote impartiality?References Shariff, A.F., Norenzayan, A. 2007. God is watching you: Priming god concepts increases prosocial behavior in an anonymous economic game. Psychological Science, 18(9), 803-809. Purzycki, B.G., et al. 2016. Moralistic gods, supernatural punishment and the expansion of human sociality. Nature, 530, 327-330. Turchin, P., Gavrilets, S. 2009. Evolution of complex hierarchical societies. Social Evolution & History, 8(2). Botero, C.A., et al. 2014. The ecology of religious beliefs. PNAS, 111(47), pp. 16784-16789.