By David P. Barash

from GeneWatch 26-4
Aug-Oct 2013

No biologist - indeed, no well-educated and thoughtful person - can be in any doubt that human beings are the product of evolution by natural selection. Nonetheless, close attention to Homo sapiens reveals a number of evolutionary mysteries, aspects of our shared humanity that are almost certainly a result of "nature" (i.e., evolution by natural selection), but whose precise evolutionary causation is currently obscure. Among these mysteries of "human nature," one of the more perplexing - and fraught - is the question of religion.

Of course, it is not guaranteed that human religiosity has evolved at all, in the biological sense. There is considerable variability in religious practices worldwide, which at least opens the possibility that the underlying causation is simply cultural tradition and social learning, which vary from place to place - as does, for example, human language. But even as culture and social learning obviously determine the detail of what particular language is spoken by what particular people, it is also true that all 'normal' human beings end up speaking some sort of language; moreover, these languages typically share what linguists designate a "deep structure." This basic pattern seems likely to apply to religion, too. Thus, the simple fact that religion is what anthropologists call a "cross-cultural universal" could suggest that it derives from another, underlying cross-cultural universal: shared aspects of the human genome.

But what?

The most obvious possibility is a "God gene." Although such a gene was purportedly discovered more than a decade ago, subsequent research has been unable to confirm this claim. Far more likely is a general, genetically influenced tendency to accept authority, to venerate designated leaders, to be positively influenced by ritual (especially when socially shared), and so forth. Nonetheless, the evolutionary mystery in this case goes beyond the need to locate one or more presumed religion-promoting alleles. Even in the unlikely eventuality that one or more such genes could be identified, a deeper and more interesting mystery remains: why would any religion-promoting genetic system have been evolved?

As philosopher Daniel Dennett has pointed out, if we see a large mammal rooting around in the mud, it is reasonable to conclude that it is seeking food; i.e., the adaptive significance of such behavior is easy to imagine. But if the animal regularly interrupts such a clearly adaptive activity to do somersaults, we are legitimately inclined to ask why. Looking, for example, at Muslims interrupting their lives to pray five times each day, at Jews refusing to use electricity or even ride in a car on their Sabbath, at Hindus circumnavigating the 52 km route around holy Mt. Kailash making full-body prostrations on their knees the entire way, or Christians donating 10% of more of their income to their churches, evolutionists cannot help seeing the biological equivalent of truffle-pigs doing cartwheels. In short, it is not biologically satisfying to conclude that religion exists because of a "religion gene" - even in the unlikely event that such a gene or gene complex exists - because this begs the question of why evolution has favored it.

Many different hypotheses can be suggested to explain the evolutionary mystery of religion. Following is an abbreviated list of some of the more intriguing possibilities. These are examined at greater length, along with other, similar mysteries such as the existence of art, consciousness, our large brains, along with a panoply of sexual puzzles, in my book Homo Mysterious: Evolutionary Puzzles of Human Nature (2012, Oxford University Press).

A Viral Meme

One possibility is that religion exists and has been promoted despite being maladaptive, or at least because its biological payoff is enjoyed not by those people who participate in various religions, but instead by the unit(s) that are the cultural equivalent of genes; namely, memes. Whereas genes are entities of nucleic acid that reside in living bodies, memes are entities of memory and information that reside in society. Genes are inherited biologically, via reproduction; memes are acquired culturally, via teaching and imitation. Genes are Darwinian, projected across generations via reproduction and spreading by the process of organic evolution; memes are Lamarckian, acquired characteristics that are "inherited" culturally, passed along from ancestors to descendants, from parent to child as well as from adult to adult, rapidly and nongenetically via conversation, imitation, songs, schooling, books, radio, television, YouTube, email, Twitter, Facebook and, yes, religious indoctrination.


Another possibility is that religion has evolved because natural selection has favored the ability on the part of our ancestors to interpret causation in the world around us. It is clearly adaptive for a creature, if sufficiently intelligent, to know the causes of things, especially when these things have important consequences for the creature in question: a gazelle likely to run away and/or to be found in particular habitats, a sabre-tooth liable to pounce, another hominin inclined to compete or to mate, and so forth. The next step, then, could well be a tendency to carry such interpretations farther than any actual situation would necessitate, and therefore seeing "agency" in the world, not only when it is really there but even when it isn't, especially when potentially directed at ourselves and thus important to us. "We find human faces in the moon, armies in the clouds," wrote David Hume in The Natural History of Religion, "and by a natural propensity, if not corrected by experience and reflection, ascribe malice and good will to every thing that hurts or pleases us." And sometimes, not just to those things that hurt or please us, but to every thing, period.

The idea, in brief, is that human beings are especially prone to detect or imagine that these worldly agents are directed toward us. Sometimes they are, after all, and when this is the case, better safe than sorry. A rustling in the grass could be a field mouse or a poisonous snake. In such cases, better to assume that such stimuli are in fact aimed at us, since the consequence of being wrong could be serious. The result would then be a human penchant for wielding an array of Hyperactive Agent Detection Devices (HADD), which aren't devices for the detection of hyperactive agents but rather detection devices that are themselves hyperactive, readily perceiving "agency" in the universe. This hypothesis, like that of viral memes, is uncongenial to believers since it suggests that although Agency Detection Devices were adaptive (and probably still are), when it comes to religion, they overshoot and as a result, we've been HADD.

Theory of Mind

Related to the Overshoot Hypothesis, but more specific, is one based on what psychologists call Theory of Mind (ToM). Basically, this is a comparatively advanced mental capacity and one that has almost certainly been adaptive: the ability to "mind read," to create a mental map of what someone else is thinking, and therefore what they are likely to do. The next step - and one that perhaps is necessarily connected to ToM - could well be a tendency to attribute mind and intentionality to various other phenomena such as volcanoes, hurricanes, tornadoes, thunder and lightning, droughts, floods, and so forth, which, unlike another person or an animal, lack intentionality but lend themselves to efforts by observant human beings to modify or propitiate them.

The Big Brain Effect

Another consequence of having a big brain (which itself presumably evolved for a variety of possible reasons, including efficient communication, planning, tool use, sophisticated mate selection, elaborate child care, etc.) could well have been a felt need to explain things, including some - such as death, questions of "meaning" in life, perplexing weather events, and so forth - that don't readily lend themselves to scientific answers. As anthropologist Clifford Geertz pointed out, people simply cannot look at the world "in dumb astonishment or blind apathy," so they struggle for explanations - objectively valid or not - resulting inevitably in religious beliefs.

Closely connected to the Big Brain Effect is the widespread and highly adaptive propensity of people, especially when young, to learn from adults and others in authority. After all, a species with a lot to learn must be predisposed to accept instruction. Thus, regardless of what actually generates religiosity among adults, once present it is likely to be avidly taken up by subsequent generations. After all, adults have much of value to transmit to their offspring: what foods to eat and what to avoid, who is a friend and who an enemy, rules of social interaction as well as language itself. It is therefore no coincidence that children are overwhelmingly prone to adopting other traditions from their parents, including the latter's religious persuasion, even though in some cases, such learning might not be biologically adaptive. Related to this, and not entirely independent from it, would be Freud's suggestion in The Future of an Illusion that religious belief is an "infantile neurosis" in which the young search for substitutes to their developmentally more primitive (but nonetheless biologically appropriate) perception that their parents are all-wise and all-powerful.

Group Coordination

Religiosity is not simply a matter of individual persuasion; a crucial aspect of nearly all religions is their social dimension. In short, religious belief might serve an adaptive role by coordinating individual actions and even inducing some individuals to engage in certain behavior (such as self-sacrifice during war) that convey a benefit to the group. This hypothesis is especially controversial among evolutionary biologists, since it is widely accepted that natural selection is only effective at the level of individual organisms and their genes, rather than between groups. This is because "altruistic" behavior directed at other group members - unless the recipients are genetic relatives - would be strongly selected against within such groups. Nonetheless, it is at least possible that "group selection" might have been uniquely effective among Homo sapiens, especially when it comes to religion, since human beings are unusual among animals in being able to enforce group norms, something that is especially characteristic of many religions, among which apostasy tends to be severely punished.

Other group-level social benefits of religion are also imaginable: reducing the proportion of freeloaders, enhancing communication among believers, raising confidence in each other's behavior, and so forth.

God as Alpha Male

It is also possible that religious belief - and particularly faith in one or a small number of very powerful deities - derives from a this-worldly primate tendency to worshipfully obey a dominant leader, who normally provides defense, facilitates access to certain necessities of life, and is dangerous to disobey. Just as many non-human primates maximize their fitness by almost literally bowing to one or a small coalition of dominant individuals, similar obeisance to one or more imagined (or real) dominant deities might be similarly favored. There seems little doubt that numerous payoffs can be derived by those followers (of religion no less than a dominant and successful secular leader) who participate in a group whose shared followership results in greater coherence and thus, enhanced biological and social success.

A Role for Consciousness?

Another group-related payoff to religiosity might be connected to what appears to be the uniquely human level of individual consciousness. As individuals evolved greater self-awareness (the adaptive value of which constitutes yet another evolutionary mystery, but one for which there are numerous hypotheses), they might well have become increasingly aware of the extent to which their personal, self-oriented inclinations differ from what is optimal for the larger social group. As a result, insofar as natural selection was somewhat driven by group selection, it is possible that religion, with its supra-individual norms, could have effectively imposed restraints and models that conscious individuals - however reluctantly - might have followed, in the interest of serving the "greater good." And of course, we cannot rule out the possibility that what many religions represent as the greater good is often a benefit accruing to a small number of individuals - not uncommonly, religious leaders themselves. Similar, therefore, to the "viral meme" hypothesis, it could be that certain especially powerful and charismatic religious leaders simply succeed in manipulating their less powerful and more compliant followers.


There is a common denominator uniting the last few hypotheses we have just considered: namely, that religious commitment involves forswearing certain personal gains while benefitting other individuals. Insofar as this basic pattern has contributed to the evolution of religious belief and practice, the puzzle of religion's origin corresponds with another puzzle: the evolution of altruism. This, in turn, opens up a whole series of theoretical and empirical questions, beyond the scope of the present article, but suggesting how what appears to be a single evolutionary mystery rapidly ramifies into numerous others.

According to historian Edward Gibbon, writing roughly a century after Locke, "The various modes of worship which prevailed in the Roman world were all considered by the people as equally true; by the philosopher, as equally false; and by the magistrate, as equally useful." Most observers of religion agree that when it comes to morality and ethical behavior, the balance sheet of most religions is difficult to interpret, although it is plausible that the "usefulness" of religion extends to natural selection (operating possibly on groups), no less than to Roman magistrates (presumably operating via its effect on rendering social relations more predictable and citizens more law-abiding). Religions certainly claim to be a source of positive moral values, and they are typically perceived as such by their proponents. On the other hand, religious persuasion can be a source of intolerance and violence, and no small amount of hypocrisy. However, it is one thing to ask whether, on balance, religions are morally beneficial, and something different to inquire whether they are biologically beneficial by virtue of their ethical teachings and the social confidence and coherence - whether objectively justified or not - that they generate.

In summary, the jury is still out on whether religion evolved at all (i.e., whether religiosity is in any direct way underpinned by genotype), and if it is, whether its evolution proceeded via group selection, which, in turn, might have favored those groups that were more violently cohesive during war and morally cohesive during peace. In my opinion, however, it is highly likely that natural selection, whether acting at the level of individuals or of groups, has been responsible for the existence as well as the perseverance of religion.

Religion poses other genetic puzzles. For example, religious fundamentalists - from a variety of different faiths - consistently oppose birth control, which raises the question of whether there exists a gene-connected susceptibility to fundamentalist beliefs, with natural selection favoring such a propensity. There is no question, in any event, that Homo sapiens presents many as-yet-unsolved evolutionary mysteries, of which religiosity itself - fascinating as it is - represents only one.

David P. Barash, PhD, is a Professor of Psychology at the University of Washington. He has written numerous books on animal behavior, evolutionary psychology, and Peace Studies.

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