This would have been a major issue in prehistory. As hunter-gatherer groups grow, they need to be able enforce a punishment mechanism – but the greater the size of the group, the less chance there is of being found out.

Enter full-access agents: “We don’t see what you do on Saturday night, but there is somebody who does, so beware,” as Dunbar puts it.

This idea was consonant with the intuitive mental tools such as HADD and intuitive morality, so it was well-received by our ancestors’ evolved brains. Plus it had the added bonus of regulating behaviour from the bottom up.

“You always get better behaviour from individual commitment,” says Dunbar, “not coercion.”

As I argued in the first part of this series, morality predates religion, which certainly makes sense given what we know about the very old origins of empathy and play. But the question remains as to why morality came to be explicitly connected with religion. Boyer grounds this connection in our intuitive morality and our belief that gods and our departed ancestors are interested parties in our moral choices.

“Moral intuitions suggest that if you could see the whole of a situation without any distortion you would immediately grasp whether it was right or wrong. Religious concepts are just concepts of persons with an immediate perspective on the whole of a situation.”

Say I do something that makes me feel guilty. That’s another way of saying that someone with strategic information about my act would consider it wrong. Religion tells me these Someones exist, and that goes a long way to explaining why I felt guilty in the first place. Boyer sums it up in this way: “Most of our moral intuitions are clear but their origin escapes us… Seeing these intuitions as someone’s viewpoint is a simpler way of understanding why we have these intuitions.” Thus, Boyer concludes, religious concepts are in some way “parasitic upon moral intuitions”.

***

We tend to think of religious beliefs as the result of individual minds, but they’re actually quite social. This isn’t surprising since, as I’ve been arguing in both parts of this essay, religion emerges from an evolutionary process that pressured apes to become more social.

But the problem created by increased sociality is its maintenance, as Dunbar explains. Before our ancestors settled into villages, they could simply “move from the Joneses to the Smiths’ group when tensions arise”. After settlement, however, they faced a very serious problem: “how to prevent everybody from killing each other”. Enter grooming.

The bonding process is built around endorphin systems in the brain, which are normally triggered by the social grooming mechanism of touch, or grooming. When it comes to large groups, says Dunbar, touch has two disadvantages: you can only groom one person at a time; and the level of intimacy touch requires restricts it to close relationships.

Recent data caps wild primates’ daily maximum grooming time to about 20 percent of their activity. Dunbar calculates that this cap limits group size to fewer than 70 members, which is significantly less than the group capacities of modern humans, at about 150. The problem, then, was to find a way to trigger social bonding without touching. Laughter and music were good solutions, which Dunbar says create the same endorphin-producing effects as grooming by imposing stress on muscles. Language works, too, a theory Dunbar has explored at length in his book Grooming, Gossip, and the Evolution of Language. Because these effects can be achieved sans touch, social bonding can happen on a much larger scale.

Dunbar’s argument is that religion evolved as a way of allowing many people at once to take part in endorphin-triggering activation. Many of the rituals associated with religion, like song, dance, and assuming various postures for prayer, “are extremely good activators of the endorphin system precisely because they impose stress or pain on the body”.