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  • Writer's pictureCarl Hodgetts

Newly discovered stone tool-use in chimpanzees may throw light on ancient human rituals

It was over 50 years ago when Jane Goodall first discovered wild chimpanzees using tools. This moment redefined the connection between humans and animals; tool use was supposedly a uniquely human ability. Since this discovery, researchers have also observed chimpanzees using stone tools to crack shells and chop large fruit into more manageable chunks. The benefit of such behaviours is pretty clear: they provide tangible and tasty snacks. Scientists, however, may have stumbled across a new form of tool wielding behaviour that may have something in common with more symbolic, ritualised behaviours in humans.

A new study, published in Scientific Reports, focused on a behaviour known as stone throwing. Stone throwing has only been seen anecdotally in nonhuman primates, and seemed to be limited to displays of male dominance. They approached their study more systematically: not unlike ourselves, chimpanzees appear to have cultural traditions, where certain types of tool use are limited to specific groups. Because of this, it is important to sample beyond a limited number of observation sites. In this case, researchers were able to monitor a large number of chimpanzee groups as a part of the revolutionary PanAf Programme –the first great-ape census to be carried out across sub-Saharan Africa.

By using camera traps across many chimpanzee communities, they saw something quite remarkable. Chimpanzees were seen to approach specific hollow trees, grab a rock, and hurl it at the tree. These were not isolated displays of dominance; chimpanzees were seen to repeat the behaviour — a behaviour with no clear or tangible benefits.

There seems to be two possible explanations. First, this could be a version of the typical male display. It is easy to see why hurling stones could make an impact on male rivals, particularly in open woodlands where sound travels easily. Interestingly, however, this behaviour was also seen in a juvenile and a female.

The second explanation is more symbolic. This stone-flinging behaviour led to distinctive stone piles, reminiscent of the cairns built by our ancient ancestors to mark boundaries and pathways. An intriguing, and yet unanswered, question is how these stone piles relate to both the geography of the environment and the chimpanzees' territories.

More interestingly, could this be a ritual of some kind? The repetitive behaviour — combined with a strong association with a particular place — bears striking similarity to human ritual practices. Before we get too carried away in thinking that chimps believe in God, there is much more work to be done. For instance, it is unclear how exactly these findings relate to man-made stone piles found in human rituals, including indigenous west African people who are known to create similar stone collections at “sacred” trees.

While major questions remain about the spiritual world of our fellow primates, it is undeniable that these pioneering studies across many great-ape communities is certain to throw light on ourselves, our history, and our link with animals.


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Original piece written Mar 10, 2016

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