If I have done my softening-up work well, you will already have completed my argument about child brains and religion. Natural selection builds child brains with a tendency to believe whatever their parents and tribal elders tell them. Such trusting obedience is valuable for survival: the analogue of steering by the moon for a moth. But the flip side of trusting obedience is slavish gullibility. The inevitable by-product is vulnerability to infection by mind viruses. For excellent reasons related to Darwinian survival, child brains need to trust parents, and elders whom parents tell them to trust. An automatic consequence is that the truster has no way of distinguishing good advice from bad. The child cannot know that 'Don't paddle in the crocodile-infested Limpopo' is good advice but 'You must sacrifice a goat at the time of the full moon, otherwise the rains will fail' is at best a waste of time and goats. Both admonitions sound equally trustworthy. Both come from a respected source and are delivered with a solemn earnestness that commands respect and demands obedience. The same goes for propositions about the world, about the cosmos, about morality and about human nature. And, very likely, when the child grows up and has children of her own, she will naturally pass the whole lot on to her own children — nonsense as well as sense — using the same infectious gravitas of manner.

On this model we should expect that, in different geographical regions, different arbitrary beliefs, none of which have any factual basis, will be handed down, to be believed with the same conviction as useful pieces of traditional wisdom such as the belief that manure is good for the crops. We should also expect that superstitions and other non-factual beliefs will locally evolve — change over generations — either by random drift or by some sort of analogue of Darwinian selection, eventually showing a pattern of significant divergence from common ancestry. Languages drift apart from a common progenitor given sufficient time in geographical separation (I shall return to this point in a moment). The same seems to be true of baseless and arbitrary beliefs and injunctions, handed down the generations — beliefs that were perhaps given a fair wind by the useful programmability of the child brain.

Religious leaders are well aware of the vulnerability of the child brain, and the importance of getting the indoctrination in early. The Jesuit boast, 'Give me the child for his first seven years, and I'll give you the man,' is no less accurate (or sinister) for being hackneyed. In more recent times, James Dobson, founder of today's infamous 'Focus on the Family' movement,*) is equally acquainted with the principle: 'Those who control what young people are taught, and what they experience — what they see, hear, think, and believe — will determine the future course for the nation.'⁷⁹

But remember, my specific suggestion about the useful gullibility of the child mind is only an example of the kind of thing that might be the analogue of moths navigating by the moon or the stars. The ethologist Robert Hinde, in Why Gods Persist, and the anthropologists Pascal Boyer, in Religion Explained, and Scott Atran, in In Gods We Trust, have independently promoted the general idea of religion as a by-product of normal psychological dispositions — many by-products, I should say, for the anthropologists especially are concerned to emphasize the diversity of the world's religions as well as what they have in common. The findings of anthropologists seem weird to us only because they are unfamiliar. All religious beliefs seem weird to those not brought up in them. Boyer did research on the Fang people of Cameroon, who believe…

Boyer continues with a personal anecdote:

Assuming that the Cambridge theologian was a mainstream Christian, he probably believed some combination of the following:

What would an objective anthropologist, coming fresh to this set of beliefs while on fieldwork in Cambridge, make of them?

The idea of psychological by-products grows naturally out of the important and developing field of evolutionary psychology.⁸⁰ Evolutionary psychologists suggest that, just as the eye is an evolved organ for seeing, and the wing an evolved organ for flying, so the brain is a collection of organs (or 'modules') for dealing with a set of specialist data-processing needs. There is a module for dealing with kinship, a module for dealing with reciprocal exchanges, a module for dealing with empathy, and so on. Religion can be seen as a by-product of the misfiring of several of these modules, for example the modules for forming theories of other minds, for forming coalitions, and for discriminating in favour of in-group members and against strangers. Any of these could serve as the human equivalent of the moths' celestial navigation, vulnerable to misfiring in the same kind of way as I suggested for childhood gullibility. The psychologist Paul Bloom, another advocate of the 'religion is a by-product' view, points out that children have a natural tendency towards a dualistic theory of mind. Religion, for him, is a by-product of such instinctive dualism. We humans, he suggests, and especially children, are natural born dualists.