If the argument of this chapter is accepted, the factual premise of religion — the God Hypothesis — is untenable. God almost certainly does not exist. This is the main conclusion of the book so far. Various questions now follow. Even if we accept that God doesn't exist, doesn't religion still have a lot going for it? Isn't it consoling?

Doesn't it motivate people to do good? If it weren't for religion, how would we know what is good? Why, in any case, be so hostile? Why, if it is false, does every culture in the world have religion? True or false, religion is ubiquitous, so where does it come from? It is to this last question that we turn next.

Everybody has their own pet theory of where religion comes from and why all human cultures have it. It gives consolation and comfort. It fosters togetherness in groups. It satisfies our yearning to understand why we exist. I shall come to explanations of this kind in a moment, but I want to begin with a prior question, one that takes precedence for reasons we shall see: a Darwinian question about natural selection.

Knowing that we are products of Darwinian evolution, we should ask what pressure or pressures exerted by natural selection originally favoured the impulse to religion. The question gains urgency from standard Darwinian considerations of economy. Religion is so wasteful, so extravagant; and Darwinian selection habitually targets and eliminates waste. Nature is a miserly accountant, grudging the pennies, watching the clock, punishing the smallest extravagance. Unrelentingly and unceasingly, as Darwin explained, 'natural selection is daily and hourly scrutinising, throughout the world, every variation, even the slightest; rejecting that which is bad, preserving and adding up all that is good; silently and insensibly working, whenever and wherever opportunity offers, at the improvement of each organic being'. If a wild animal habitually performs some useless activity, natural selection will favour rival individuals who devote the time and energy, instead, to surviving and reproducing. Nature cannot afford frivolous jeux d'esprit. Ruthless utilitarianism trumps, even if it doesn't always seem that way.

On the face of it, the tail of a peacock is a jeu d'esprit par excellence. It surely does no favours to the survival of its possessor. But it does benefit the genes that distinguish him from his less spectacular rivals. The tail is an advertisement, which buys its place in the economy of nature by attracting females. The same is true of the labour and time that a male bower bird devotes to his bower: a sort of external tail built of grass, twigs, colourful berries, flowers and, when available, beads, baubles and bottle caps. Or, to choose an example that doesn't involve advertising, there is 'anting': the odd habit of birds, such as jays, of 'bathing' in an ants' nest or otherwise applying ants to the feathers. Nobody is sure what the benefit of anting is — perhaps some kind of hygiene, cleaning out parasites from the feathers; there are various other hypotheses, none of them strongly supported by evidence. But uncertainty as to details doesn't — nor should it — stop Darwinians from presuming, with great confidence, that anting must be 'for' something. In this case common sense might agree, but Darwinian logic has a particular reason for thinking that, if the birds didn't do it, their statistical prospects of genetic success would be damaged, even if we don't yet know the precise route of the damage. The conclusion follows from the twin premises that natural selection punishes wastage of time and energy, and that birds are consistently observed to devote time and energy to anting. If there is a one-sentence manifesto of this 'adaptationist' principle, it was expressed — admittedly in somewhat extreme and exaggerated terms — by the distinguished Harvard geneticist Richard Lewontin: 'That is the one point which I think all evolutionists are agreed upon, that it is virtually impossible to do a better job than an organism is doing in its own environment.'⁷⁵ If anting wasn't positively useful for survival and reproduction, natural selection would long ago have favoured individuals who refrained from it. A Darwinian might be tempted to say the same of religion; hence the need for this discussion.

To an evolutionist, religious rituals 'stand out like peacocks in a sunlit glade' (Dan Dennett's phrase). Religious behaviour is a writ- large human equivalent of anting or bower-building. It is time-consuming, energy-consuming, often as extravagantly ornate as the plumage of a bird of paradise. Religion can endanger the life of the pious individual, as well as the lives of others. Thousands of people have been tortured for their loyalty to a religion, persecuted by zealots for what is in many cases a scarcely distinguishable alternative faith. Religion devours resources, sometimes on a massive scale. A medieval cathedral could consume a hundred man- centuries in its construction, yet was never used as a dwelling, or for any recognizably useful purpose. Was it some kind of architectural peacock's tail? If so, at whom was the advertisement aimed? Sacred music and devotional paintings largely monopolized medieval and Renaissance talent. Devout people have died for their gods and killed for them; whipped blood from their backs, sworn themselves to a lifetime of celibacy or to lonely silence, all in the service of religion. What is it all for? What is the benefit of religion?

By 'benefit', the Darwinian normally means some enhancement to the survival of the individual's genes. What is missing from this is the important point that Darwinian benefit is not restricted to the genes of the individual organism. There are three possible alternative targets of benefit. One arises from the theory of group selection, and I'll come to that. The second follows from the theory that I advocated in The Extended Phenotype: the individual you are watching may be working under the manipulative influence of genes in another individual, perhaps a parasite. Dan Dennett reminds us that the common cold is universal to all human peoples in much the same way as religion is, yet we would not want to suggest that colds benefit us. Plenty of examples are known of animals manipulated into behaving in such a way as to benefit the transmission of a parasite to its next host. I encapsulated the point in my 'central theorem of the extended phenotype': 'An animal's behaviour tends to maximize the survival of the genes "for" that behaviour, whether or not those genes happen to be in the body of the particular animal performing it.'