Group Level Selection? The Non-Evolution of Religion

There are a number of scholars who claim that “religion” evolved as an adaptation.  What kind of adaptation? A group level adaptation. The story usually goes like this: at some unknown time during the middle or upper Paleolithic, certain groups of hominins developed proto-religious beliefs. These beliefs, which are rarely if ever specified, somehow gave rise to more cooperative and prosocial behaviors that made the group more cohesive. More cohesive groups, in turn, makes the group more competitive vis-à-vis other groups. There might be more altruism and sharing (i.e., “moral” or “ethical” behavior), or individuals might be more committed and selfess, presumably making the group more efficient at foraging or warfare.

While this makes for a plausible story, there are a number of problems. The first is that we have little archaeological evidence of ritual behaviors, especially those that would have been group oriented. While some have argued that evidence of symbolic thinking – in the form of decoration-adornment and markings on material objects – indicates ritual behavior, this linkage is attenuated at best and imaginary at worst. While wearing perforated shell or decorating material objects is suggestive, such displays neither entail nor require ritual-religious behavior.

A simpler explanation is that people were using such items as social markers, to individuate themselves and perhaps signal to others identity or status. There remains a large gap between these artifacts and the kinds of group ritual activities, such as singing and dancing, that some have imagined. While such data do not rule out ritual or proto-religious behaviors, they constitute sparse evidence for ruling them in.

Bigger Groups Win

The second major problem – the one I wish to focus on here, concerns competition between groups. What makes one group more successful than another?  In nearly all cases involving competing groups of social mammals, larger groups out-compete smaller ones.  The reasons are fairly obvious and supported by the evidence: larger groups have lower predation risk and have greater success in agonistic encounters between groups. They have larger ranges or territories, and when resources are depleted or disappear, migration – usually a hazardous undertaking, is more feasible. When a larger group of social mammals encounters a smaller one, the larger nearly always prevails. Larger groups also have a greater store of collective knowledge with respect to nearly everything that matters – water, food, shelter, and predators.

While there are several factors that impact group size, ecological ones being foremost, it is safe to say that ritualistic or proto-religious behaviors are not among them.  Highly social mammals are for the most part bound together by that most powerful of evolutionary bonds: genetic kinship.  Extraneous factors need not be invoked to explain cooperative or even altruistic behavior.  Inclusive fitness is sufficient.

Talking about Tools

Focusing specifically on hominins, there are two factors that would have decisively impacted the size and ultimate success of Paleolithic groups: language and technology. One need not accept the “social grooming” hypothesis to realize that language (or advanced forms of proto-language) is a game changer when it comes to cooperation and cohesion.  In addition to the planning and coordination it would have enabled, language at some point made possible notions of extended and fictive kinship, further strengthening this most powerful form of social glue.

For at least 2.5 million years and probably longer, technology has been a defining characteristic of hominins. Although there are broad progressive technological trends in the lithic record, it is also clear there were long periods of stasis and even reversion. Few things would have had a greater impact on any given group’s odds of success than its technologies. Although apparently slight advances (such as material choice and flaking methods) were undoubtedly advantageous, other technologies were – like language – game changers. The control of fire is obviously one of these. The first groups to develop composite weapons, spear throwers, and bows-arrows would have had immense advantages over other groups, not only in hunting but also in warfare. For groups radiating toward northern latitudes, clothing would have provided similar benefits.

In sum and in rough order of importance to the success of any given hominin group, the factors that would have had the greatest impact intergroup competition are: (1) group size; (2) proto-language or language; and (3) technology. Any group having advantages in one or more of these areas would have been better able to compete against groups deficient in them, but which might have had the kind proto-religion or ritual that enhances group solidarity and commitment.  Such solidarity and commitment is, of course, determined in the first instance by kinship, which is not dependent on proto-religion or ritual for its efficacy.

It seems unlikely that proto-religion or ritual provided any groups with advantages with respect to language or technology. No one has ever suggested that language evolved or technology progressed because either was linked to the supernatural. Given this fact, and the paramount importance of group size to group success in ancestral environments, the critical question facing advocates of group level selection as the functional impetus for the evolution of religion is: Did proto-religion enable Paleolithic hominins to form larger groups? If group ritual oriented around supernatural beliefs somehow resulted in larger groups, then the “religion evolved as a group level adaptation” story may have legs.

Paleolithic Group Size – No Religion Necessary

Let us assume, for the sake of argument, that at some point during the middle or upper Paleolithic, certain groups developed proto-religious ideas that promoted ritual activities and resulted in increased cooperation or cohesion. Do we have any reason to think that such ideas or activities also resulted in larger groups, which the single best predictor of success when it comes to group competition? While we can speculate on the ways in which proto-religion might have affected group size, a better method is to look for evidence that hominin group sizes increased during the Paleolithic. If we can identify increases in group size among Paleolithic hunter-gatherers, we can then ask whether the larger groups were enabled or caused by proto-religion.

Because we do not have direct evidence of Paleolithic group size, we have to rely on proxies and analogies, however imperfect. As a proxy, we can examine primate group size. For an analogy, we can examine known hunter-gatherer groups. Although primates obviously do not have anything like proto-religion, it is reasonably safe to assume that the factors affecting primate group size are similar to those that would have affected hominin group size. As for known hunter-gatherers, they do have something akin to “religion,” although their loosely organized, non-systematic, and individualized shamanic practices bear few resemblances to the kinds of religions that humans systematically developed in conjunction with agriculture. If we can identify groups that grew over time or were larger than others, we can ask whether the observed size increase was connected to supernatural-religious beliefs, or whether other factors better explain the larger groups.

Because there are over 300 species of extant primates, it should come as no surprise that group size (and composition) varies considerably; the range is from a few family members to a few hundred. While several variables affect group size, the most important are predation risk, resource density, and neocortex size. The latter speaks to the tremendous load that intense sociality places on cognition and memory.

Chimpanzees and baboons are perhaps the most relevant models; the former because they are the most closely related to hominins and the latter because they are largely terrestrial and live in relatively stable multi-male and multi-female groups. Many researchers are of the opinion that this mode and composition most closely resembles the ancestral hominin condition. Chimp group size varies from 15 to 65 and the mean, other factors being equal, is approximately 30. Baboon group size varies from 25 to 250, with a mean near 100.

Remarkably, these numbers are quite similar to those of known hunter-gatherers. The basic foraging unit – which usually includes a few related families – consistently clusters around 30 people. This group typically maintains close ties to neighboring groups that are similarly sized and genetically related. The units occasionally aggregate into a group that averages 150 members, most of whom are related. This fairly tight knit group is primary, and is the one that can be counted immediately counted on in times of need. In most cases, these primary groups of 150 maintain kinship ties with surrounding groups of similar size, with the result being that a kinship group of approximately 500 constitutes the larger regional network that may come together only infrequently. This secondary group is typically the largest and hunter-gatherer groups rarely exceed this number. Beyond the regional network group of 500, relations are attenuated and conflict more likely. This pattern (basic = 30, primary = 150, secondary = 500) is fairly consistent across time and space.

This consistency in forager group size, when coupled with similar group sizes for chimps and baboons, leads to the conclusion that the upper limits of hominin group size remained relatively stable for much of human evolution. These limits and groupings were, of course, substantially altered by the dynamics of domestication; with agriculture and sedentism, human group size increased substantially. It is at this time, when groups become larger than 30-150-500, that kinship glue is no longer able to hold people together, and collective abstractions – such as polity or religion – are required to maintain larger groups. For most humans in the world, this fundamental transition (from foraging to agriculture) occurred no more than 7,500 years ago.

No Group Evolution of “Religion”

Where does this leave us? It means there is no need to invoke religion or ritual to explain group level success. Given the limited group sizes we are talking about for most of human evolution, other factors – such as language and technology – would have had far more profound effects on the success of one group versus another. Kinship, both real and fictive, is more than sufficient to bind such limited-size groups together and make them cohesive, cooperative, and altruistic. This is not to say that proto-religion and ritual would not have had an impact, but it is difficult to imagine the circumstances under which a “religious” 30 member group would prevail over a “non-religious” 150 member group. If group sizes were equal, and one group was proto-religious but the other was not, other factors would have been more decisive in determining the outcome of any conflict between them.

It is only when all primary variables are equal – group size, linguistic ability, and technological prowess – that a proto-religious group may have had some kind of advantage due to increased cohesion or cooperation. This places religion far down on the list of factors that explain group success during the Paleolithic. It also means that “religion” did not evolve because it made some groups more competitive than others.


Aiello, Leslie and Dunbar, Robin. 1993. “Neocortex Size, Group Size, and the Evolution of Language.” Current Anthropology, 34(2):184-193.

Baer, Darius and McEachron, Donald. 1982. “A Review of Selected Sociobiological Principles: Application to Hominid Evolution — The Development of Group Social Structure.” J. Social Bio. Struct., 5:69-90.

Isbell, Lynne and Young, Truman. 1996. “The evolution of bipedalism in hominids and reduced group size in chimpanzees: alternative responses to decreasing resource availability.” Journal of Human Evolution, 30:389–397

Janson, Charles and Goldsmith, Michele. 1995. “Predicting Group Size in Primates: Foraging Costs and Predation Risks.” Behavioral Ecology, 6(3):: 326-336.

Kosse, Kristinza. 1989. “Group Size and Societal Complexity: Thresholds in Long Term Memory.” J. Anth. Arch., 9:275-303.

Marlowe, Frank. 2005. “Hunter Gatherers and Human Evolution.” Evolutionary Anthropology, 14:54 –67.

Wrangham, Richard, et al. 1993. “Constraints on Group Size in Primates and Carnivores: Population Density and Day-Range as Assays of Exploitation Competition.” Behavioral Ecology and Sociobiology, 32(3)199-209.

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16 thoughts on “Group Level Selection? The Non-Evolution of Religion

  1. Pingback: Group Level Selection? The Non-Evolution of Religion « Geoff's Blog

  2. Pingback: Proto-Religious Foragers v. Non-Religious Foragers

  3. Pingback: Sizing Up Kinship: Larger Groups Win

  4. admin Post author

    Are you saying that nation-states are religious groups? Or that exceptionally large hunter-gatherer groups — such as many Plains Indians tribes — are held together by “religion”? If it was “religion” that bound individual members of a tribe together, then why did opposing tribes essentially share the same “religion” (i.e., the guardian spirit complex coupled with the Sun Dance ceremonial)?

  5. Pingback: The Sins of an Evolutionary Psychologist

  6. J. A. LeFevre

    (Chris: I wrote this on seeing the title to this post, before reading. It addresses the title only. My many arguments for ‘adaptation’ will strike randomly, with your leave – as the stars direct me)
    D. S. Wilson has a blog on ‘’ where he posts regular (very defensive) arguments for ‘group selection’ (a bit touchy on that topic is he). The challenge, it seems, is to define the problem properly, then arguments fall into or out of place. The first evidence of (aboriginal) religion, as presented by National Geographic (‘oldest ritual?’) – is pegged at about 70,000 years back. The present day locals appear to be honoring the same ritual patterns – not much evolution here. I don’t see much development in society or religion until we get to the Neolithic and the development of organized religion.

    Now organized religion has priests and no individual can support a staff of priests – it takes a group. In the beginning, all villages and all city-states held a single religion, and the benefit of that first religion is that it allowed that city to form. Also, in the beginning, each emerging civilization invented their own religion (so we now have variation which evolution requires), and soon, as the cities and their influence expand, we have competition – the second ingredient of natural selection. The religion, then, which motivates its believers most effectively will see its community (group) prevail and its religion spread. Over time, this group level characteristic evolves, trying new forms (sects if you will and periodic conversions to something new) and competing with rivals.

    Sounds to me like group level selection – at the cognitive/cultural level – not at the gene level as the people (and genes) migrate between groups constantly.

  7. admin Post author

    National Geographic is not exactly a “source.” As an initial matter, you need to define “religion” before talking about it in the context of the Paleolithic. We can’t look at modern (post-Neolithic) “religions” and just project them backwards in time. This is an invalid procedure.

    What we today call “religion” has a deep history, and earliest evidence for which might be deliberate burials, with grave goods. See my posts on burials and let’s talk.

  8. J. A. LeFevre

    National geographic was not the source, but a host. I have not found the original for a time. I thought I made it clear that I was only looking from the Neolithic forward (on this post).
    I do not (at this point) equate burials with religion – burials can serve hygienic and safety (to not attract predators) motives as well as simple affection/respect.

  9. admin Post author

    Then what is the NatGeo reference to “religion” at 70,000 years ago? Is it the single piece of incised ochre found in South Africa? This, along with the other Howieson’s Poort materials, don’t really constitute evidence of religion.

  10. J. A. LeFevre

    Take a look. It is a cave with a carved stone python (and other less impressive art), a hidden chamber and still used by the San in their rituals. I recall an ‘interview’ with one of their shaman where he described some of the significance of the various symbols found in the cave, but I do not see that in this Nat-Geo summary.

  11. admin Post author

    I will take a look. The dating appears to be a problem. There are no carvings, cave paintings, or art known from 70,000 years ago. The first evidence of these types of things, at least solid evidence indicative of regular activity, is about 45,000 years old. This is a reasonably good starting point for the development of the earliest shamanic practices.

  12. J. A. LeFevre

    ‘Earliest’ is always going to be a moving target and dating is never exact. Once we believed ‘modern’ first appeared in Europe, but more recent findings show and earlier appearance in Africa.

  13. admin Post author

    We have some fairly tight dates for the appearance of items associated with shamanism — about 45,000 years ago.

  14. Anonymous

    Religion is too abstract. You’d do better to use the term “a punitive god” or “a moralizing god (or gods)”

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