ISSR is currently running a major research project on Religion and the Social Brain, directed by Michael J. Reiss and co-ordinated by myself, with a grant of £759,320 from the Templeton Religion Trust. The ‘social brain’ theory of human evolution has been developed by Robin Dunbar, a Fellow of ISSR, who is one of the key researchers on the project. Other ISSR Fellows working on it are Léon Turner and Miguel Farias. There are subgrants to the University of Oxford and to Coventry University.

‘Social Brain’ is a broad approach to human evolution, unlike the Cognitive Science of Religion which focuses specifically on religion. There is an outline of the Social Brain theory in Dunbar’s Pelican Introduction to Human Evolution. Though he takes a view of how and why religion evolved, he nests that in a broader view of human evolution. For Social Brain theory, religion is not an incidental feature of human evolution; it is crucial to the success of human evolution. It does not press the question of whether religion was a by-product or adaptation, and would be inclined to say that it was both.

One of the challenges facing emerging humanity was how to deliver social cohesiveness across much larger group sizes than were possible to maintain by mutual grooming, which was the main method used by our primate ancestors. Mutual grooming has its attractions, but it is hugely time consuming, and is only feasible in quite small grooming circles. Larger group sizes would have been much better for hunter-gatherer life, if they could be made sufficiently cohesive.

The solution was trance dancing, with synchronised rhythmic movements undertaken by a largish group of people. Such patterns of movements trigger massive endorphin release in the whole community; collective endorphin release in turn delivers very good social bonding. In that sense, trance dancing was crucial to the success of human evolution; it was of real benefit.

Endorphins seem to be the social neuropeptide, unlike oxytocin which is much more individualistic. Endorphins are social in two senses. The most powerful triggers of endorphin release often involve collective activities. The synchronous movements of eight rowers in a boat are a classic sporting example, and trance dancing also involves similar synchronisation. In addition, endorphins contribute to social bonding and cohesiveness. They build up the experience of being part of a tightly-knit group, with all the loyalties and mutual concern that go with that.

Different kinds of religion have gone about social regulation in different ways. There has been much interest in evolutionary theories of religion in fear of supernatural punishment. Social Brain theory sees that as a feature of later, more doctrinal forms of religion, associated with more frequent but less intense rituals. Trance dancing delivers social regulation in a more positive way, through facilitating social bonding.

The evolution of religion arises within some complex patterns of co-evolution. Having larger social groupings, with more complex structures, demanded enhanced cognitive capacities (including theory of mind), which in turn demanded expanded frontal lobes. On this view, brain size, cognitive capacities and social structures developed together. None of them represent the key change from which everything else flowed. They evolved together. Unlike the Cognitive Science of Religion, Social Brain theory includes cognition in these developments of emerging homo sapiens, but it does not give primacy to cognition. It has a more systemic, inter-related view of how religion evolved. The emergence of religion both depends on and facilitates other developments.

From a Social Brain perspective, religion evolved gradually and rather piecemeal, and it is debatable when it should properly be called ‘religion’. However, the Social Brain approach is clear that it started with embodied practices rather than with cognition; cognition seems to be one of the later aspects of religion to develop, and the cognitive aspects of religion start with narrative before they become doctrinal. Robert Bellah takes a similar view of how religion evolved. Trance dancing was the soil out of which religion emerged, as the endorphin release triggered by trance dancing also triggered various transcendent experiences. Reflection on those exceptional experiences led to a religious worldview.

In Social Brain theory, religion played a central role in human evolution. However, the Social Brain perspective on religion and evolution has not yet been fully developed. That is what we are attempting in our ISSR project. The project has multiple strands. It will culminate in an integrative book from Robin Dunbar on religion and evolution, but there are various strands of research that are feeding in to that.

One of these strands involves phylogenetic analyses of ethnographic databases such as the Puloto database and the Relations Area Files database. Joseph Watts is examining the possibility that changes in ritual and the complexity of religion across Austronesian societies correlate with changes in community and tribe (i.e. language community) size and/or social complexity. We are doing separate analyses of ethnographic databases to look at the role of song and dance rituals, Black Magic and religious professionals.

We are also doing research on contemporary religion. Some of this is naturalistic, looking at markers of endorphin release as a result of church services and how it correlates with increases in feelings of group bonding. We want to understand which kinds of services do that and which don’t, and what it is about church services that can transform people in these ways. Key questions are: (if) How is the endorphin system stimulated by religious rituals and to what extent does it facilitate the social bonding processes of religious groups? (ii) Why do religious rituals, which are rooted in a range of behaviours that facilitate social bonding, acquire specifically religious dimensions?

We are also undertaking some lab studies in which we can investigate this in more tightly controlled conditions. Our initial assumption is that to get the effects of religion in the lab we need an activity that is: (i) likely to trigger endorphin release; (ii) one which lends itself to being seen in religious terms; (iii) which is performed by religiously minded people; and (iv) that they are primed to see in religious terms.

One of the best known aspects of Social Brain theory is ‘Dunbar’s number’ (150), which seems to represent some kind of limit on the size of a viable social network. It is actually one of a series of numbers in Social Brain theory that represent transition points in social networks. 150 seems to be the largest number of people you can get to know, but it is sufficiently large number to deliver some of the excitement of mass activities. It is the point at which intimacy and a mass movement meet.

That is leading us to investigate the significance of Dunbar’s number for contemporary religious life, and to connect it with congregation size theory. Interestingly, congregation size theory also seems to have recognised that 150 is a crucial transition number, and the maximum size for a unified pastoral-type congregation. To go beyond that, some restructuring seems to be needed, with different congregations nested within a single church.

We are examining historical databases on congregation size and finding some support for this. We are also examining church planting from this point of view, looking at when new plants are launched, and how they grow in size. We have preliminary indications that they often stabilise at around Dunbar’s number. This line of research will give a much stronger theoretical basis to work on congregation size, which has so far been rather intuitive and a-theoretical.

We are also exploring the broader philosophical and theological implications of the Social Brain approach to religion. We hope that the Social Brain approach to religion will enrich our understanding of religion in significant ways and address criticisms that have often been levelled at the evolutionary study of religion from the other disciplines in the human sciences. One of the things that makes the Social Brain approach theologically congenial is that it is not committed to the radical individualism that is a feature of many other approaches. Its social approach sits well with the emphasis on relationality in much recent theological anthropology.

We hope that an evolutionary approach to religion, grounded in Social Brain theory will help to integrate theological and evolutionary perspectives on human nature and relationality. There seems to be real potential for Social Brain theory to inform theological discussions of contemporary human community, and the fragmentation of personal identity and society.

We will report further on the project as our research progresses, and will include reports in a conference that ISSR is planning for the summer of 2019.