This month brought us the news that chimps might be religious.
This bizarre conclusion is hard to draw from the episode that provoked it; however, we can say, fairly confidently, that chimps sometimes display behaviours that have no clear purpose or function.
Scientists from the Humboldt University of Berlin set up camera traps in chimp territory in the Republic of Guinea, and found the the chimps placed rocks in the hollow of a tree, and bashed the tree with rocks.
It is not clear what the chimps are doing this for, but it’s possible that the footage demonstrates chimps engaging in ritual; this could be the evolutionary origin of religion.
This is by no means the first time we’ve seen chimps behave strangely, in ways that possibly demonstrate symbolic behaviours we did not expect them to be capable of. In 2010, the New Scientist reported that chimps in Uganda’s Kibale National Park had been spotted using sticks as toys. The behaviour was more common in females, and seemed to indicate that chimps selected doll-shaped sticks and treated them as dolls, playing with them and making nests for them to sleep in. Sonya Kahlenberg of Bate’s College, Maine, remarked that this could reasonably be assumed to be practise for motherhood.
So what purpose could placing stones in trees possibly serve the chimp family? How can we interpret this bizarre behaviour? Banging the rocks against the tree makes a loud noise, so could be a way of showing dominance or communicating to other chimps; but why store the rocks in the hollow – convenience, perhaps? Chimps are expert tool-makers and they are capable of using a variety of objects to accomplish some function to aid the survival of the group, but it is hard to see what functional purpose this apparently ritualistic behaviour could serve.
Although chimps have frequently been observed using stones to crack open nuts, or to display dominance and demonstrate their place within the group, this footage does not seem to fit within these establish behaviours; they are not doing this to gain food or status.
Laura Kehoe, who took part in the research, suggests the following theories:
The behaviour could be part of a male display, where the loud bang made when a rock hits a hollow tree adds to the impressive nature of a display. This could be especially likely in areas where there are not many trees with large roots that chimps would normally drum on with their powerful hands and feet. If some trees produce an impressive bang, this could accompany or replace feet drumming in a display and trees with particularly good acoustics could become popular spots for revisits.
On the other hand, it could be more symbolic than that – and more reminiscent of our own past. Marking pathways and territories with signposts such as piles of rocks is an important step in human history. Figuring out where chimps’ territories are in relation to rock throwing sites could give us insights into whether this is the case here.
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.