Chimpanzee nut cracking leaves telltale marks on stones, providing clues to human evolution

[Judi Lynn]

by Kate Hull on 13 December 2022

The dents and dings on the surfaces of rocks used by chimpanzees to crack open nuts preserve a history of how the animals used the tools and how those patterns change from one troop to the next, researchers reported recently in Royal Society Open Science. This archaeological data can offer insights into the ways similar stone tool technology arose millions of years ago among hominins, the ancestors of humans.

Scientists examined nut-smashing rocks used by chimpanzees (Pan troglodytes verus) in Taï National Park, in southwestern Côte d’Ivoire in West Africa. Measurements and 3D scans of the tools revealed distinct patterns of damage related to how the animals wielded the rocks.

The team then compared these marks to those from prior study that described nut-cracking tools used by chimpanzees about 300 kilometers away in Bossou, Guinea — the only other study to examine tools in this way. Even though the Guinea chimps used their stone tools for the same purpose, differences in the damage patterns clearly showed which tools came from which troop.

The study focused on “percussive” tools used for hitting or pounding. Most archaeological research on tool use has focused on “flake” technology — tools used for cutting and slicing. However, percussive tools probably came first, researchers believe.

Studying the details of how chimpanzees use percussive tools today helps researchers better understand hominin behavior from over 2 million years ago, said lead author and archaeologist Tomos Proffitt of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. Hominins then were “running around and cutting things, but also, similarly to chimpanzees, probably cracking open nuts,” Proffitt said.

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A Djouroutou chimpanzee cracks open a panda nut on a wooden anvil. Photo credit: Liran Samuni, Taï Chimpanzee Project

More:
https://news.mongabay.com/2022/12/chimpanzee-nut-cracking-leaves-telltale-marks-on-stones-providing-clues-to-human-evolution/