Written by Robin Dunbar


Review by Steve Minett

This is a book about religion through the lens of evolutionary psychology. The author, Robin Dunbar, gives two definitions of religion; firstly, Durkheim’s, that religion is a “unified system of practices accepted by a moral community – a group of people who share s set of beliefs about the world.” In other words, “religion is something that people do” The second is more philosophical or psychological, “religion is a comprehensive worldview, a set of beliefs, that is accepted by a community as being true without need of evidence – religion as something that a group of people believe.” (p.xvi) Also in the introduction, Dunbar identifies two fundamental characteristics of religion: it is a universal feature of all human cultures. Second, all religions are subject to fragmentation: over time (often very short periods) any religion is likely to split into many sub-variants. (p.xvii) Dunbar links the origin of religion to ‘mystical trance’, which has three distinct features; “a susceptibility to enter trance-like states, a belief in the existence of a transcendental (or spirit) world, and a belief that we can call on hidden power(s) to help us.” He suggests that trance-like states may be, “a by-product of the way the human mind is designed.” (p.26) He also suggests that trance arises from the fear of death and from, “accidents of experience (such as epileptic fits) or the use of mind-altering drugs.” (p.32) Trance underlies the original, ‘animist’ form of religion, which later developed into more sophisticated ‘doctrinal’ forms.

As to the evolutionary function of religion, Dunbar identifies this as the promotion of sociality and community solidarity, i.e. altruism and a general willingness to help others and share with them. Dunbar believes that this doesn’t come naturally to us, especially in the case of non-kin others. So, as human groups grew in size, doctrinal religions were required to admonish us to such pro-social behaviour. In other words, human groups need bonding and the bigger the group the better the bonding has to be. On the other hand, bigger groups were beneficial for humans in order to counter external threats, such as predation and raiding by other human groups. To regulate the inevitable frustrations and conflicts of big group life, religion came up with a ‘Moralising High God’, “who acts as an all-seeing policeman in the sky.” (p.58) God was particularly effective in this role, since he is omniscient and omnipotent, took an interest in human affairs and punishes rule-breakers. The emergence of a ‘Moralising High God’ enabled larger communities to exist by keeping the lid on fractiousness. (p.93)

Another way of expressing this explanation for the existence of religion is what Dunbar calls the ‘social brain hypothesis’: primates have significantly larger brains for their body size than any other group of species. This, “additional computing power is needed to mange the dynamic complexity of their bonded social groups.” (p.80) For example, primate interactions are not simple ‘dyadic relationships’ as they are in anonymous herds: if you consider threatening another group member, you have to be aware as to how their family and friends in the group may react. This complexity increases exponentially with the size of the group, and, among primates, human groups have the biggest groups, at around 150 individuals. According to Dunbar, in groups of this size, the evidence suggests that, “a religious ethos somehow enables the members to keep a lid on the fractiousness and squabbles that inevitably arise in small communities, thereby preventing the community from tearing itself apart.” (p.92)

Dunbar takes another approach to this explanation of religion as a method of group bonding by looking at primate grooming. Monkeys and apes use social grooming to generate group bonding, but as Dunbar points out, there’s a physical limit to the number of individuals a group member can regularly groom, which he sets at around fifty. Human hunter-gather groups were (and are) fewer than fifty individuals. However, unlike most primate groups, they are, “… embedded in higher-level groupings  – several camp groups make up a community, several communities a mega-band, several mega-bands a tribe.” (p.99) In order to bond at this scale, which requires a series of behaviours which trigger the collective activation of the endorphin system, humans evolved the following group activities; “laughter, singing, dancing emotional storytelling, feasting (communal eating and the social drinking of alcohol) and last but not least, the rituals of religion.” (p.102)

Part of the function of a ‘Moralising High God’ was also to allow elites to maintain control over the product of others’ labour. (p.193) This raises the question as to whether the appearance of such a ‘God’ required a certain level of political complexity. The implication is that such forms of doctrinal religion were only possible after the agricultural revolution. Even then, Dunbar notes that many recent analyses distinguish between two forms of post-agricultural religion: in the first form, rituals were necessary to appease capricious deities, who weren’t really interested in the moral behaviour of individuals. (The Aztecs provide an example of this form.) The Abrahamic religions characterise the alternative form, where the Moralising High God takes an active interest in the, “… wellbeing and behaviour of their human worshippers, rewarding those that adhere to the rules … and punishing (now or in the world after death) those who don’t.” (p.194/195) 

Dunbar even provides a quantifiable threshold, a population of around one million, at which High Gods appear, “… indicating that they are associated with empires rather than city states and so … [managed] … very large sociopolitical stresses.” (p.197) Reaching this level of population density is associated with what has become know as the ‘Axial Age’, which is associated with the foundation of the great world religions of today. In a similar spirit of quantifiability, Dunbar quotes a study suggesting that this period of religious innovation was triggered when annual per capita energy production reached around 20,000 kcal. The large-scale doctrinal religions of the Axial Age, with their emphasis on good behaviour and individual responsibility, precipitated, “… a switch from a largely lawless society to one in which the rule of law applies and ideologies develop that encourage citizens to behave prosocially.” (p.198) For example, to prohibit stealing from others. 

The last two chapters of the book deal with cults, charismatic leaders and schisms, in great historical details, right up to contemporary events. (There are detailed accounts, for example, of the cult leaders, Jim Jones and David Koresh.) Having followed Dunbar’s cogent and coherent account of the evolutionary function of religion, these detailed, historical accounts appear rather out of place in this book. I can conclude by suggesting that any reader like me (a humanist with an interest in evolutionary psychology) would do well to skip these final chapters, while benefitting greatly from the rest of the book.

Published by Penguin Random House, 2022, 329PP, ISBN 978-0241431795