In it, Boyer reviews some of the key cognitive biases that lead to religious beliefs. For example, our tendency to form 'social' bonds with inanimate or imaginary entities, the ritualization of cleanliness and, importantly, our 'coalitional' psychology:
This coalitional psychology is involved in the dynamics of public religious commitment. When people proclaim their adherence to a particular faith, they subscribe to claims for which there is no evidence, and that would be taken as obviously wrong or ridiculous in other religious groups. This signals a willingness to embrace the group’s particular norm for no other reason than that it is, precisely, the group’s norm.Boyer thinks that the 'byproduct' explanation of religion is the most probable, based on the current evidence:
So is religion an adaptation or a byproduct of our evolution? Perhaps one day we will find compelling evidence that a capacity for religious thoughts, rather than ‘religion’ in the modern form of socio-political institutions, contributed to fitness in ancestral times. For the time being, the data support a more modest conclusion: religious thoughts seem to be an emergent property of our standard cognitive capacities.He concludes:
The findings emerging from this cognitive evolutionary approach challenge two central tenets of most established religions. First, the notion that their particular creed differs from all other (supposedly misguided) faiths; second, that it is only because of extraordinary events or the actual presence of supernatural agents that religious ideas have taken shape. On the contrary, we now know that all versions of religion are based on very similar tacit assumptions, and that all it takes to imagine supernatural agents are normal human minds processing information in the most natural way. Knowing, even accepting these conclusions is unlikely to undermine religious commitment. Some form of religious thinking seems to be the path of least resistance for our cognitive systems. By contrast, disbelief is generally the result of deliberate, effortful work against our natural cognitive dispositions — hardly the easiest ideology to propagate.