A recent study performed in the tropical rain forests of Western Africa has generated a lot of interest and discussion into ancient chimpanzee cultures. The excavation of stone tools dating back 4,300 years has changed a lot of preconceived notions about how chimps acquired this food gathering technique. Modern chimps use large, heavy granite stones to pummel Panda nuts to extract the fruit within the hard exterior shell. The history of chimps performing this task previously dated back only to the 19th century, so many experts believed that this technique was developed from chimps imitating humans. The new stones, excavated by a team led by Julio Mercader of the University of Calgary, predate any known human inhabitants of Noulo at Cote d'Ivoire in the Ivory Coast's Tai National Park. Researchers had previously theorized that chimps learned this technique from ancient humans, and this imitation was passed down through generations. If chimps manufactured and used tools without the presence of humans, it can now be theorized that chimps either developed this idea independently as a result of independent technological convergence, or chimps may share a common ancestor with early humans that first learned this pummelling technique.
The dig was conducted in the only known ancient chimpanzee rain forest settlement. Researchers dug down several meters to find charcoal samples that indicated that sedimentary depositions from the area dated back 4,300 years. From the dig, researchers collected 206 stones that exhibited unnatural chipping characteristic of repetitive pummelling. These stones were mixed with other similar naturally broken stones and tested by three examiners. These specialists of ancient stones proved the collected stones were not geofacts and indeed broken by a physical force applied by an agent. The stones averaged 12.6 inches in length, 4.5 pounds in weight, and most of them were Granite. All three of these characteristics correlate to the average rock parameters preferred by modern local chimps when choosing a pummelling stone. The size of hands required to slam such a large stone and the starch residues found on the rocks indicate that the original agent was chimp rather than human. So if these stones were in fact used by ancient chimps in the late stone age, what light can be shed onto the development of their culture and intellect during this prehistoric time.
In order to smash a fruit with a stone, a certain extent of socialization and culture must be implied. Simple tasks such as selection of proper rocks and movement of the rock to where the fruit is located is somewhat simple. But the social network that is required for the passing down of this complicated action from one generation to the next should not be underestimated. Previous studies conducted by one of the scientists involved with the dig, Christoph Boesch, suggest that modern chimps undergo a seven year internship with elder members of the troop in order to successfully pummel their own fruit. There would need to be a significant accumulation of generations practicing this technique before it became established enough to generate 206 pummeling stones in the same area. If you consider the rocks dated back 4,300 years, they should indicate that the roots of primate intelligence run much deeper and older than previously estimated. It was found in the 1980's by Jane Goodall that chimps are capable of considerable understanding, but it is now apparent that they have been exhibiting characteristics of established culture for thousands of years.
Mercader, J., Barton, H., Gillespie, J., Harris, J., Kuhn, S., Tyler, R., Boesch, C. (2007). 4,300-Year-old chimpanzee sites and the origins of percussive stone technology. Proceedings of the National Academy of Sciences, 104(9), 3043-3048. DOI: 10.1073/pnas.0607909104