Chimpanzees from different regions constantly show new types of behavior. Credit: Mark Linfield/Walt Disney Pictures, CC BY

Scientists Spot Chimps Doing Mystery Ritual: Have They Entered Their Own Stone Age?

Are chimpanzees evolving?


Scientists are well aware that chimpanzees are masters in the use of “auxiliary tools.” They use branches and sticks to reach ants and termites, digging their nests. They also use stones to break walnuts and other nuts, and so on. This behavior has been observed in monkeys living in their natural habitat, as well as among those in zoos. It has long been believed that chimpanzees do all this simply because they want to get food.

More to be learned

The variety of manipulations that monkeys use has led scientists to believe that there is much more to be learned about the social culture of chimpanzees if the observations involve a larger number of families from different regions and communities. This is how the Pan African Programme (PanAf) was born, thanks to which scientists have discovered something amazing and interesting: chimpanzees in certain regions have shown a rare behavior that includes piling up stones in various locations. Such behavior has led scientists to believe that chimpanzees have rudimentary cultural rituals.

Real footage taken during the observations shows a male chimpanzee throwing a large rock at a tree. Scientists suggest that this could be some sort of a new ritual. Credit: MPI-EVA PanAf/Chimbo Foundation
Real footage taken during the observations shows a male chimpanzee throwing a large rock at a tree. Scientists suggest that this could be some sort of a new ritual. Credit: MPI-EVA PanAf/Chimbo Foundation

A strange behavior akin to a ritual

Primatologists from the Max Planck Institute for Evolutionary Anthropology and colleagues from other research centers have been observing the behavior of monkeys from several dozen locations across Africa for several years. To avoid disturbing the animals with their presence, the scientists used several different surveillance options – masked surveillance cameras and similar technologies. Experts describe stone piles gathered near tree trunks or in hollows at the base of trees.

A pile of stones

Moreover, it seems like the stones are purposefully piled in chambers. There is footage that shows a chimpanzee coming from somewhere, taking a stone – either from the pile itself or lying nearby – and throwing it at a tree while also making a distinctive sound. The “ritual” is performed mainly by older males, but younger males and females have also been spotted. Scientists believe this is exactly how the piles of stones were formed in such places. Before they gather enough in the tree’s hollow or the pile becomes large enough, the chimpanzees carry the stones from another place and begin using the accumulated “stock.”

Ritualistic behavior?

Another behavior is possible – first, collect enough stones for a prolonged period, then periodically come to the place and throw the stones on the marked tree. Two clarifications need to be made. First, such behavior is not ubiquitous: stone piles have been found in only four of the thirty-nine sites observed. In other words, in some populations, chimpanzees perform this “ritual,” while in others, it is not practiced.

A compilation of images from the observations showing how the monkey throws stones and then the pile of rocks within the tree. Credit: Kühl et al [2016]
A compilation of images from the observations showing how the monkey throws stones and then the pile of rocks within the tree. Credit: Kühl et al [2016]

Actions that scientists still can’t understand

Secondly, and more importantly, is that the meaning of this action remains incomprehensible to scientists. Through this manipulation, chimpanzees do not acquire food; they have no spectators to impress, meaning that it has nothing to do with their rituals of attracting a sexual partner. The absence of anyone to see what is happening precludes the option that they seek approval (although the issued roar accompanying the throwing of the stones is heard far enough away).


Evolving monkeys?

The presence or absence of stone piles does not depend on whether there are “stocks” of such in the area or the availability of “suitable” trees. Before the launch of the large-scale PanAf project, such behavior was not observed, which does not mean that chimpanzees recently invented it. Of course, many would say that the chimps are just doing nonsense. However, science does not accept such explanations, especially since we have a clear example of the opposite – humans.

Similarity to human-made cairns?

Homo sapiens do things daily that can easily be described as “doing nonsense,” but if someone calls the things you do “Wasting time,” you would disagree with him. The study’s authors suggest that the stone piles created by chimpanzees may be similar to the human-made cairns. This is a term that archaeologists use to call the artificial structures in the form of a chamber of stones – often conical – known since prehistoric times of humankind.

Various purposes

People erected cairns for various purposes – they used them as landmarks or to mark where someone’s remains were buried. In 2017, scientists reported something unique for the first time – they observed chimpanzees perform funerary rights. A pair of chimps were caught attending to a dead relative with “tools” to clean their body. One of the elder chimps was cleaning the teeth of her “adopted son” after he passed away. Such behavior has been observed in the past but never in the case of a dead chimp.

Learning more about these “rituals”

By all means, there is much more to learn about chimpanzees than we currently know. These “rituals” and behavior may sound like something normal that we may haven’t noticed in the past, but it is highly unlikely. To me, it seems certain groups are evolving or changing their behavior to something that resembles what we do as humans. Could certain individuals have entered their Stone Age?

Differences in similarities

Of course, the abovementioned behavior does not refer to all chimpanzees worldwide. After all, humans also did not evolve with the snap of a finger. Certain groups evolved and led the rest. If we believe that we originated from certain primates, why exclude the possibility that monkeys may be evolving too? This reminds me of several studies and experiments from a few years ago.

Playing God

Although I consider them rather inhumane, scientists inserted human brain genes in monkeys’ brains, and the results proved that their brains had shown signs of human-like development in time. Scientists then compared normal monkeys with genetically modified specimens in a series of memory tests. As you can guess, the monkeys with human genes showed much better results. Perhaps, in the end, humans and monkeys may be even more closely related than science understands, or the latter may be catching up with their development. Only time and long-term observations can give us the answers we seek.


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Daley, J. (2016, March 07). Chimps May Be Performing Rituals at “Shrine Trees”.
Gannon, M. (2017, March 21). Cleaning Corpses: Chimpanzee Funerary Rites Seen for 1st Time.
Hooper, R. (2016, March 04). What do chimp ‘temples’ tell us about the evolution of religion?
Kühl, H., Kalan, A., Arandjelovic, M., Aubert, F., D’Auvergne, L., Goedmakers, A., . . . Boesch, C. (2016, February 29). Chimpanzee accumulative stone throwing.
Perry, P. (2019, January 30). Scientists have captured chimpanzees performing a bizarre ritual.
Shi, L., Luo, X., Jiang, J., Chen, Y., Liu, C., Hu, T., . . . Su, B. (2019, March 27). Transgenic rhesus monkeys carrying the human MCPH1 gene copies show human-like neoteny of brain development.

Written by Vladislav Tchakarov

Hello, my name is Vladislav and I am glad to have you here on Curiosmos. As a history student, I have a strong passion for history and science, and the opportunity to research and write in this field on a daily basis is a dream come true.

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