Do chimps have “sacred” rituals?

March 1, 2016 • 10:00 am

Reader Ant called my attention to a piece by Laura Kehoe in The Conversation, detailing “accumulative stone-throwing behavior” in chimpanzees living in the Republic of Guinea. Kehoe describes a behavior, caught on a camera trap, that she and others eventually wrote a paper about:

What we saw on this camera was exhilarating – a large male chimp approaches our mystery tree and pauses for a second. He then quickly glances around, grabs a huge rock and flings it full force at the tree trunk.

Nothing like this had been seen before and it gave me goose bumps. Jane Goodall first discovered wild chimps using tools in the 1960s. Chimps use twigs, leaves, sticks and some groups even use spears in order to get food. Stones have also been used by chimps to crack open nuts and cut open large fruit. Occasionally, chimps throw rocks in displays of strength to establish their position in a community.

But what we discovered during our now-published study wasn’t a random, one-off event, it was a repeated activity with no clear link to gaining food or status – it could be a ritual. We searched the area and found many more sites where trees had similar markings and in many places piles of rocks had accumulated inside hollow tree trunks – reminiscent of the piles of rocks archaeologists have uncovered in human history.

Videos poured in. Other groups working in our project began searching for trees with tell-tale markings. We found the same mysterious behaviour in small pockets of Guinea Bissau, Liberia and Côte d’Ivoire but nothing east of this, despite searching across the entire chimp range from the western coasts of Guinea all the way to Tanzania.

Here’s a video of the behavior:

NOTE: The video seems to have disappeared, but you can download several videos from the paper’s supplementary information at this site.

In the article, Kehoe suggests this could be a surrogate (and louder) form of chest-thumping, or serve to mark the territory of a chimp band. But she goes further, into the territory of the numious:

Even more intriguing than this, maybe we found the first evidence of chimpanzees creating a kind of shrine that could indicate sacred trees. Indigenous West African people have stone collections at “sacred” trees and such man-made stone collections are commonly observed across the world and look eerily similar to what we have discovered here.

That, of course, is going to garner all the press. Chimps show rudiments of religion! Well, I have to confess that I haven’t yet read the multi-authored paper in Nature (link and reference below), but here’s the abstract:

The study of the archaeological remains of fossil hominins must rely on reconstructions to elucidate the behaviour that may have resulted in particular stone tools and their accumulation. Comparatively, stone tool use among living primates has illuminated behaviours that are also amenable to archaeological examination, permitting direct observations of the behaviour leading to artefacts and their assemblages to be incorporated. Here, we describe newly discovered stone tool-use behaviour and stone accumulation sites in wild chimpanzees reminiscent of human cairns. In addition to data from 17 mid- to long-term chimpanzee research sites, we sampled a further 34 Pan troglodytes communities. We found four populations in West Africa where chimpanzees habitually bang and throw rocks against trees, or toss them into tree cavities, resulting in conspicuous stone accumulations at these sites. This represents the first record of repeated observations of individual chimpanzees exhibiting stone tool use for a purpose other than extractive foraging at what appear to be targeted trees. The ritualized behavioural display and collection of artefacts at particular locations observed in chimpanzee accumulative stone throwing may have implications for the inferences that can be drawn from archaeological stone assemblages and the origins of ritual sites.

Here’s a figure from the paper(click to enlarge):

Caption (from the paper): (a) Adult male chimpanzee tossing a stone; hurling a stone (Boé, Guinea-Bissau); and banging a stone (Comoé GEPRENAF, Côte d’Ivoire). (b) Boé, Guinea-Bissau landscape: stones accumulated in a hollow tree; a chimpanzee accumulative stone throwing site; and stones accumulated in-between buttress roots (see also Supplementary Movies 1–7).

The paper describes the behavior as performed predominantly by males, which suggests that it’s an extension of male “drumming” rather than a symbolic “shrine” at “sacred trees,” as the authors suggest in the discussion. (To be fair, they don’t seem to favor one hypothesis over another.) Have a look at the video, read the short paper, and weigh in below. Is this the rudiments of religion, or some kind of appreciation of the sacred?


H. S. Kühl et al. 2016. Chimpanzee accumulative stone-throwing. Nature Scientific Reports 6, Article number: 22219 (2016), doi:10.1038/srep22219

67 thoughts on “Do chimps have “sacred” rituals?

  1. The Stoning of the Devil (Arabic: رمي الجمرات‎ ramī al-jamarāt, lit. “stoning of the jamarāt [place of pebbles]”)[1][2][3] is part of the annual Islamic Hajj pilgrimage to the holy city of Mecca in Saudi Arabia. Muslim pilgrims throw pebbles at three walls (formerly pillars), called jamarāt, in the city of Mina just east of Mecca. It is one of a series of ritual acts that must be performed in the Hajj. It is a symbolic reenactment of Abraham’s hajj, where he stoned three pillars representing the temptation to disobey God and preserve Ishmael.

  2. Cannot resist a bit of sarcasm:

    Whether ‘religious behaviour’ or not, it does exhibit approximately the level of thoughtfulness shown by most humans, when practicing religion.

      1. “We’ll be saying a big hello to all intelligent lifeforms everywhere and to everyone else out there, the secret is to bang the rocks together, guys.”

  3. The more likely explanation is that all mammals have a Landscaping Instinct. Humans, for example, evolved hands to hold hedge clippers, etc.

  4. Are bower birds performing religious rituals with their bowers?

    Seems like a misfire of the agency detection feature (on the part of the researchers).

    1. At the very least, it’s certainly a mistake to interpret any ritualistic behavior as “sacred” or “religious”, although I can see how simple ritualistic behaviors in early humans could’ve contributed to the emergence of religion.

    2. But unlike the chimp behavior, which seems to have no relation to food gathering or mating per the article, the bower birds build their bowers to bedazzle and bewitch female bower birds.

    3. I agree. What test could one perform that would identify the varying hypotheses? As it stands now, I’m not inclined to think the religious ritual hypothesis has much validation.

  5. I watched and read this yesterday. This could be a form of ritual or even some kind of mating ritual, but I am skeptical that is has anything to do with religion or sacred behavior.

    I enjoy the sound of a wood bonging, so why wouldn’t they appreciate too. Maybe this is the start of Frederic Chopin Chimp.

    1. The sound was my first thought. The musicality of the particular trees chosen is obvious (and I wonder if that is a factor in the reported range of the behavior). The puzzling thing to me, though, is how they throw/drop/plant their rock and run. You’d think if they liked the sound, or if they were using the sound to mark territory, that they’d do it multiple times in a row.

      1. Maybe they’ve learned that the sound attracts rivals, or predators, or dinner. Maybe they make the sound to see what’s attracted to it…

  6. I think both hypotheses — drumming and sacred rituals — are lame. The chimps are practicing.

  7. I saw a posting about this as well. I agree that it is more likely connected with male testosterone-laced displays of aggression, plainly visible in the expression on their faces, vocalization, stance, etc. Those parts at least are classical elements in chimp aggression displays where they try to impress others with how tough they are. Other examples where they have the same behavioral elements are done while running around, thrashing a branch through the brush, or bashing a tree with their fists or with a stick. It is interesting that the rocks accumulate, but of course chimps will copy other chimps.
    So not religion, but I can accept parallels with human behavior. Frat boys come to mind.

    1. But maybe it really is a religion. Seems like a lot of what goes on in church is just a bunch or classical aggression displays. “Follow the God I represent or he will burn you in the afterlife” is pretty damn aggressive.

  8. looks to be about as religious as scotsmen tossing the caber. Do they drink fermented bananas afterward?

  9. I think its going to be hard to tease out any ritualistic content from more pragmatic conent. For example, because these accumulations are pretty easy (for other chimps) to see, it could simply be a way to mark territory or communicate presence.

    This is not my area but I thought drumming was a more individualistic action, intended to distinguish one male chimp from others? It is hard to see how this could be analogous to drumming if a bunch of different male chimps are all throwing rocks into the same hollow stump.

  10. I’m not remotely a biologist, so take this for what it is worth. From what I have read, chimp groups will display what could be called cultural differences between them (i.e. there are different learned behaviors that are passed down between different groups). As for why this group has a “throw stones at trees” thing, I couldn’t come to a conclusion. However, I did read an interesting article about monkeys ( that sort of led me to believe that we may never know the origin of the behavior.

    Taking the water hose experiment into account, the chimps’ rock throwing could help shine some insight into the human development of religion.

  11. If we accept Durkheim’s thesis (Les formes elementaires de la vie religieuse) that religion grew out of the security attained through communal living (a feeling which could be associated with others in the group and with specific objects within the group territory), then perhaps this is evidence that such characteristics predate human society.
    I am just throwing this out for discussion. I am not sure that I would buy this explanation but on the other hand, I doubt that this behaviour can be explained by territorial marking or simple aggression.
    (I have only viewed the short video so really ought not to generalise, but it was noticeable that the female did not get too close to the tree and did not throw any rocks.)

  12. It’s not clear that the monkeys believe there is any kind of spirit or unworldly power in the tree which would be the acid test, but I am not sure how one would test such a supposition.

    If the monkeys feel this gives them some sort of sense of a fuller more complete life, it does still have some rudiments of religion.

    1. Heh, maybe one of the “atheist churches” that are cropping up should just have members lob stones through a hole in a wall instead of singing songs.

        1. And they are usually referred to as apes, not monkeys.

          Atheist churches have a very flat hierarchy, made up entirely of primates.

  13. I remember in The God Delusion by Dawkins that he wrote about an experiment on ducks (or was it geese?) where they were given food at random intervals from a food dispenser. But what happened was that the birds developed various ritual behaviors before the dispenser ‘god’, like bobbing their head or turning in place. The speculation given was that they began to associate being given food upon doing a certain behavior, so they repeated the behavior. This was said (by Dawkins) to resemble a kind of religious practice.
    This is of course an aside from the present topic, but it may be that animals have the human-like capacity to be delusional.

    1. Probably the bird in question was the pigeon, as used by B. F. Skinner. He described the developed behavior as superstitions.

      1. Yep, it was pigeons and Skinner. But I don’t understand why turning its head should be seen as superstitious. Pecking at a certain button and getting food is just as arbitrary, mysterious to a pigeon, as turning its head. I don’t get it.

        1. The dance of the pigeon is superstitious because it is completely unnecessary to get the reward. Pecking the button is the non-superstitious behavior because it is required.

    2. Wasn’t there a film of Dawkins visiting some place where they demonstrated this? I know I’ve seen a modern film of this with some science popularizer… maybe it was Brian Cox? Now I’m going crazy because I know I’ve seen it in the last 12 months but can’t find it…

  14. Have a researcher cut one of the trees down. If he/she is stoned to death by a mob of angry chimps, then it was a sacred tree.

  15. Doesn’t the Hajj pilgrimage to Mecca include a “stoning-the-devil” ritual? Perhaps these chimps have converted to Islam?

    I think we need to be on our guard against Chimpanjihad.

    1. Notice that only males are engaged in the ritual, which makes your hypothesis even stronger.

      I will be extra cautious next time I board a plane with other chimps.

  16. I don’t see the rudiments of religion or the appreciation for anything sacred. I see the rudiments of sports. I think this is behavior is performed just for the satisfaction of exerting a personal physical impact on the environment. It is just fun to throw a rock at tree trunk.

  17. While I agree that the “numinous” aspect of the interpretation is likely to garner most, if not all, of the commentary, it’s hardly there in the paper. Unless I’ve missed something (and I admit to having skipped the Methods section), the only mention of the “sacred” is in human behaviour :

    For example, stone accumulation shrines at ‘sacred’ trees are well described for indigenous West African peoples.

    (Discussion, para 3, sentence 7.)
    But that is in the context of describing plausible functional effects of these accumulations, onto which functionality the humans (as I read it) have grafted the concept of “sacred-ness”.

    (Discussion, para 3, sentence 6.)
    In fact, marking territorial boundaries and pathways with cairns has been an important
    practice of many historical human societies.

    And still, they’re putting the “numinous” conceptions in a human context, not a chimpanzee context. Or, for that matter, in the context of the last common ancestor of humans and chimps.
    So, what is going on here? Well, the association of elements of this behaviour with elements of the “hand and feet drumming” and “pant hoot” behaviours is certainly suggestive of where the roots of this behaviour. Both the drumming and the pant hoot behaviours are more uniformly widespread in chimpanzee cultures.
    Archaeologically, there are records of the Oldowan-type tools, core-stones, and working sites being concentrated in particular working sites, where they are not associated with the detritus of carcass-processing. That could certainly be a descendent of this sort of behaviour.
    What about modern-human behaviours related to this? Well, I’ve personally (i) excavated quartz-pebble strewn surfaces around an underground “ritual” site on Skye ; (ii) walked up myriads of mountains bemoaning the habit of Homo sapiens var. montanensis sub-var. lost of making little piles of rockes to mis-lead other specimens into going down dead-end ridges and into “where’s my parachute?” drops ; Why oh why do people make these little piles when they don’t really know where they are? ; (iii) walking and cycling around in the Highlands I’ve visited many sites of stone circles where some or all of the interior of the circle is floored with quartz pebbling ; (iv) do I even need to mention the myriads of long barrows and round barrows and bell-shaped barrows and burial mounds and henges and Silbury Hill (is it true that that involved more material movement than the Great Pyramid of Giza? I’ll have to check that, but it is bloody big!). And for the trans-Pondians, there’s those mud piles at Cahokia, whose culture name escapes me at the moment. Then there are the geoglyphs from the Cerne Abbas Giant through to the Zyuratkul Elk (I am SO pissed that I didn’t see that from Zyuratkul Krivet! But I did find microliths on the shore of the lake.) Do I need to go on? humans have been piling stones one on another for a long, long time. A long, long, long time. A geologically noticeable amount of time.
    (I note a comment in the paper that : We expect that the concentrated accumulation of stone tools at specific tree locations will facilitate further study of this behaviour, for example through determining site fidelity using excavations and other archaeological methods. If sites are found to be long-lived, it would represent another type of stone tool-use behaviour in chimpanzees, in addition to nut-cracking, that leaves behind an archaeological record. however, such archaeological investigation will be highly intrusive, and not compatible with examining a site currently being used by chimpanzees. Sadly, it is a safe bet that some of these non-human sophonts will be exterminated on a time scale that will allow for investigation of this point.)

  18. In addition to the other skeptical remarks, I’d add also: religion is “functional” in more socially simpler human groups (i.e., they don’t distinguish between religion and other activities) so one might want to be on the look out for this in other animals, too.

  19. Some of these comments are hilarious…..

    Well, could it be like leaving a calling card, a “Kilroy was here” sort of thing, while showing off at the same time? The bigger males seem to throw bigger rocks Iand do a kinda slam-dunk move. I also noticed that the chimp carrying the baby on board didn’t throw a rock at or into the tree, but wiped or stamped her foot on the ledge of the opening (threshold), perhaps leaving her scent behind!

    Has anyone tested for chimp blood/remains at any of the sites? I was wondering if a gruesome death took place at any of these trees, such a predator snatching a chimp as it attempted to clamber up the tree.

    1. I like the death idea. Not because I expect it’s correct, but because it would be really interesting if true.

      1. Of course, I was just speculating, while at the same time remembering how elephants gather over the bones of dead herdmates and fondle the bones with their trunks. Just wondering what it all means.

    2. Your mention of “slam dunk move” brings to mind an analogy with sports. These chimps could just be having fun and showing off.

  20. There’s so much one can think of in regards to chimp behavior with stones that may be similar to what humans (and other animals) do with stones . Humans raise cairns at “special” sites (sometimes just to indicate that you’re on the right path). Humans place stones on caskets and on graves. Humans skip stones on water. Humans throw rocks for various reasons, not aggression only. Humans make art of stone and gravel gardens. Humans fill hollows in stones, earth and trees with graffiti, stones, plants, etc. I think it’s a rather large leap to ascribe any such activities to aggression only or religion.

  21. It’s certainly possible that the ritual behavior in chimps is merely pleasurable but otherwise meaningless. In that sense humans too might possess a tendency to such behavior. Only after the evolution of more complex symbolic thought did such behavior begin to acquire supernatural significance.

    I can imagine a young caveboy asking his caveman dad, “Why do we stack rocks like this?”

    “Um…er…well, son,” the cavedad says, “we do it for the gods. Yeah, that’s it. So the gods will show us good favor.” …and the next thing you know we have the Vatican and the Crystal Cathedral.

    1. I thought what Stephen referred to was more like the following “2001” reference in a Roger Waters lyric:

      “The monkey sat on a pile of stones
      And stared at the broken bone in his hand
      And the strains of a Viennese quartet
      Rang out across the land”

      So it was a monkey, a bone, and an upwards toss in which the bone transmogrified into a space station; as opposed to chimp, stone, etc.

      But maybe I misunderstand….

      In any case it was the shallower Strauss (Johann, not Richard); an orchestra, not a quartet; and probably actors mimicking primates, not monkeys. But Roger needs some space to make poetry.

      1. But you don’t hear Strauss until the space scenes. There’s no music accompanying the hominins in that scene.

        And Richard was from Munich, later in Berlin and Meiningen — not Viennese at all.

        The film was nominated for the Oscar for best make up, but that went to _Planet of the Apes_. Clarke wondered if the Oscar committee thought that Kubrick had used real apes.


  22. This suggestion is not new re primates. A similar suggestion has been made with respect to certain behaviors of Hamadryas baboons re that were perceived as ritualistic and ‘cult-like’. But it’s a big leap (too big) from observing ritualistic animal behavior to reading ‘cult-like’ behavior into it and inferring that it expresses something inherently religious. However, I can’t recall if this was posited by a primatologist or an over-eager cultural anthropologist. Hopefully not a primatologist.

  23. Maybe there needs to be research to prove that testosterone promotes the throwing of things. Nobody denies that men LOVE throwing things. So why not primates, too? Maybe without primates showing the way -( they just like to throw things,IMHO) – human males would not play baseball or basket ball or soccer or the toss the taber or…..

    OK OK, women just LOVE to throw things, too, in recent times. Do we know that female primates never throw things? It took the human species millennia to allow females to throw things – maybe primate females are not quite there yet.

    Anyway, seems like there are many reasons why primates and humans might like to throw rocks without bringing religion in to the picture!

  24. I think it’s a Demonstration of Strength, in a similar way that they drum on the Boles of trees with their Feet, I doubt there is any Ritual intended, but you never know.

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