Researchers at the Max Planck Institute for Evolutionary Anthropology have recently found that chimpanzees use a variety of stone tools, depending on what kind of nut they want to crack.
Image credit: William D. Snyder
Hominin (human ancestor) archaeological sites tend to preserve stone tools dating back to 3.3 million years ago. These tools were used for myriad of things, but most importantly cutting and preparing food. In time, the use of these tools influenced both the cultural and biological evolution of our human ancestors.
In the 1960s, Jane Goodall famously observed a chimpanzee--whom she named David Greybeard--use a stick to fish for termites, which turned out to be the first documented tool use in non-human primates. That observation, combined with the close phylogenetic relationship with humans, made chimpanzees a good comparative model for understanding how tools are made and used by hominins. With the 2007 discovery of the “Chimpanzee Stone Age,” researchers found that chimpanzees had been making stone tools for thousands of years.
However, specific questions about how stone tools were used remain, as this is something that can only be inferred from the fossil record. As such, the researchers from Max Planck specifically studied how raw materials are used to crack open nuts.
At the Djouroutou field site in the southwest Tai National Park in the Côte d’Ivoire, a group of about 60 wild chimpanzees were found to use stone and wooden tools to open nuts. Interestingly, through various analyses, researchers found that this specific group of chimpanzees use different stone tools—like hammers and anvils—to open five different nut species. These differences in tools used are likely due to varying hardness of nut shells. Additionally, chimpanzees from other forests tend to use different percussive patterns in their tool use, further supporting the idea that the range and type of raw materials influence tool use.
Stones tend to preserve well in the fossil record meaning they can indicate past behaviors. Thus, from an archaeological perspective, there are similarities between the Djouroutou chimpanzee and Plio-Pleistocene (around 5 million years to 11,000 years BCE) percussive tools, and as such chimpanzees continue to serve as a good comparative model for human cultural evolution.