Social bonding is important, of course, to many species. But there’s an aspect of religion that seems to be peculiarly human. Being able to engage in religious discussion – and hence explain the significance of the rituals and why you should take part – depends on the kinds of mind-reading, or “mentalising”, skills that play a crucial role in managing our everyday relationships. These are the skills that allow us to understand what someone else is thinking, to grasp their intentions. They allow us to utter sentences such as, “I know that you realise that Freddie believes that …”

Mind Reading and Mentalizing

Our natural community size – the size of our personal social network, the number of friends we have on Facebook – is part of a relationship between group size and brain size in primates. Each species has a characteristic group size determined by the size of its brain. Ours is about 150. Not only is this the average size of personal social networks (the number of extended family and friends with whom you have meaningful relationships), but it also turns out to be the optimal size for religious congregations.

The Size of the Brain

A plate of bread and salt would be placed on the deceased’s lap while they were lying in repose. Just before the coffin was closed and the funeral cortege set off for the church, the village sin-eater arrived, ate the bread and was given some coins and a glass of ale for their trouble. The belief was that the deceased’s sins were absorbed by the salt and transferred into the bread, and then into the sin-eater.

Sin-Eater

In a survey I ran, those who reported attending religious services were depressed less frequently, felt their lives were more worthwhile, were more engaged with their local community, and felt greater trust towards others. These enormous benefits mean not only that religion has enduring appeal, but that religious practices make you “fit” in the evolutionary sense – and thus they tend to stick around.

Religious Services

To be able to do this, I have to be able to step back from the immediacy of the physical world so as to imagine the possibility that you might or might not think this, that Freddie might or might not intend whatever you thought he did, and even whether the person Freddie had in mind did or did not think what Freddie thought they did. Apes can do the first two steps in this chain, but that’s the limit. For humans, it comes easily, bringing with it an ability to imagine parallel worlds inhabited by invisible beings.

It’s a short step from there to religious ideas, which in turn lead to better bonding, which makes you more likely to survive. Survival means your superior mentalising skills will be passed on to a new generation, equally adept at religious thinking; a penchant for religion is therefore part of our genetic inheritance.

The Genetic Inheritance

But that’s not all. The same cognitive abilities that give us religion also allow us to ask why the world has to be the way it is (giving us science) and to imagine entirely fictional worlds (giving us literature). Thus, you could no more have a world where religion was cast aside as superstition than you could have one without science or stories. And that would be a very different world indeed.A History of God by Karen Armstrong (Vintage, £11.99)Religion Explained by Pascal Boyer (Basic Books, £14.35)World Religions – The Great Faiths Explored and Explained by John Bowker (DK, £19.99)

Fictional Worlds

Endorphins also underpin the bonding of friendships and, through that, allow us to create supportive groups of like-minded individuals. This effect seems to be especially strong in the context of rituals, as has been shown experimentally in religious services in the UK and Brazil. It seems, therefore, that religions evolved to reinforce a sense of community cohesion, something that’s extremely important to our wellbeing and survival.

Context of Rituals

Sin-eaters were usually elderly and destitute, and glad to have the money – not to mention the free food and drink. The price they paid was to be shunned by their community because of their macabre associations. The last known sin-eater was Richard Munslow, who died aged 73 in 1906. Sin-eating reminds us that, more than anything else, even the most staid of religions – in this case, Anglicanism – can be associated with surprisingly curious beliefs and rituals.

Sin-eating

Perhaps because of this, it has often been claimed that religious belief arises from ignorance and superstition. If that were the case, you might expect religion to gradually fade away as societies became better educated and more scientifically oriented.There are at least two reasons, however, why religions persist. One is the fact that, on average, religious people are generally happier, healthier and live longer. For better or for worse, they also have easier deaths when the time comes. The other is that religious people are more likely to feel that they belong to a community.

Ignorance & Superstition

Part of the reason people are attracted to religion is that its rituals – the standing, sitting and kneeling in unison, the singing, the listening to emotionally rousing sermons – trigger the brain’s endorphin system. This is the mechanism that underpins social bonding in all primates, including humans. Like opiates, endorphins produce a sense of bliss bordering on ecstasy, calmness and warmth, relaxation and trust, while elevating pain thresholds. In addition to these hedonic benefits, endorphins trigger the release of natural killer cells (part of the body’s immune system).

Religion Rituals

In 2018, archaeologists moving bodies for reburial from a 19th-century cemetery in Birmingham to make way for the new HS2 station were puzzled to find several that had plates on their laps. Then someone remembered a curious custom from the nearby Welsh Marches – that of the village “sin-eater”.

What Does Faith Have to Offer Us?

If a congregation is smaller than about 100, it puts a heavy burden on the membership; if it is above about 200, it becomes increasingly prone to divisiveness. This seems to explain why big religions are so susceptible to fragmentation – constantly throwing up small sects (typically of a few hundred people at most) built round a charismatic leader whose wayward beliefs the hierarchy desperately tries to contain.