Stone selection by wild chimpanzees shares patterns with Oldowan hominins

Area of Science:

• Primate behavior
• Archaeology
• Paleoanthropology

Background:

• Tool use for dietary flexibility is common in humans and chimpanzees (Pan troglodytes).
• Comparing ancient hominin and chimpanzee toolkits is challenging due to differing tool repertoires.
• Rock selection based on physical properties is a shared trait in primate and hominin tool use.

Purpose of the Study:

• To document stone tool selection patterns in wild chimpanzees cracking nuts.
• To investigate chimpanzee decision-making when selecting stones with varying, non-visible mechanical properties.
• To compare chimpanzee stone selection with documented hominin lithic selections.

Main Methods:

• Controlled experiments with wild chimpanzees at Bossou, Guinea, using novel rock types.
• Introducing rocks previously selected by hominins (e.g., at Kanjera South).
• Analyzing selection of anvils and hammers based on mechanical properties and task-specific functions.

Main Results:

• Chimpanzees select harder stones for hammers and softer stones for anvils.
• Selection is linked to task-specific mechanical properties, indicating discrimination of 'invisible' features.
• Adults learn through individual experience, while juveniles reuse tools; selection may be socially transmitted.

Conclusions:

• Chimpanzee stone selection demonstrates an understanding of material properties for specific functions.
• These patterns mirror Oldowan hominin rock selection behaviors.
• The study provides insights into the discrete nature of hominin stone selection in artifact production.