New paper on chimpanzee culture is out now!
An adult male chimpanzee in Bossou (Guinea) cracking oil palm nuts using a stone hammer and anvil . Photo credit: Dr. Kathelijne Koops
We used field experiments to show that chimpanzees do not simply invent nut cracking with tools, but they learn such complex cultural behaviours from others. Their culture is thus more similar to human culture than often assumed.
Humans have a complex culture that enables them to copy behaviours from others. As such, human culture is cumulative, since skills and technologies accumulate over generations and become increasingly efficient or complex. According to the zone of latent solutions hypothesis in anthropology, chimpanzees do not learn in this way, but can reinvent cultural behaviours individually. The Ape Behaviour & Ecology Group carried out novel field experiments in the Nimba Mountains of Guinea to show that this may not be the case.
Four experiments with wild chimpanzees
We investigated whether wild chimpanzees can in fact invent a complex behaviour like nut cracking independently. The chimpanzees were presented with a series of four experiments. In the first, the chimps were presented with oil palm nuts and stones. In the second, we added a palm fruit to the experimental setup. In the third, the nuts were cracked open and placed on top of the stones. In the fourth, the chimps were presented with another, easier-to-crack species of nuts (Coula) together with stones.
The chimpanzees visited the nut cracking experiments and explored the nuts and stones, yet they did not crack any nuts, even after more than a year of exposure to the materials. A total of 35 chimpanzee parties (or sub-groups) visited the experiments, of which 11 parties closely investigated the experimental items. The chimpanzees were more likely to explore the experiments when visiting in bigger parties. Only one female chimpanzee was observed eating from the palm fruit, but on no occasion did the chimpanzees crack or eat either oil palm or Coula nuts.
“Our findings suggest that chimpanzees acquire cultural behaviours more like humans, and do not simply invent a complex tool use behaviour like nut cracking on their own”
Shared evolutionary origin of cumulative culture
The presence of a model from whom to learn appears to be the missing piece. “Our findings on wild chimpanzees, our closest living relatives, help to shed light on what it is (and isn’t!) that makes human culture unique. Specifically, they suggest greater continuity between chimpanzee and human cultural evolution than is normally assumed and that the human capacity for cumulative culture may have a shared evolutionary origin with chimpanzees.