Shared Strategies: How Chimpanzees’ Stone Tool Choices Reflect Ancient Hominin Practices

Do Chimpanzees Echo the Tool-Selecting Skills of Early Humans?

Chimpanzees are well-known for their sophisticated tool use, but a new study published in the Journal of Human Evolution¹ sheds light on how their stone tool choices might mirror those of our ancient ancestors. By examining the decision-making processes behind chimpanzees’ selection of rocks for cracking nuts, researchers have uncovered striking parallels to the toolmaking behaviors of Oldowan hominins who lived over 2.5 million years ago.

The Foundations of Stone Tool Use

Oldowan hominins, who represent the earliest known stone tool users, employed rocks as choppers, scrapers, and basic cutting implements. These ancient humans didn’t grab stones at random; their choices reveal a calculated selection process likely informed by generations of shared knowledge.

Curious about whether this intentionality could also be observed in modern chimpanzees, an international team of paleobiologists, anthropologists, and behavioral scientists set out to study how these apes select and use stones for cracking nuts—a skill requiring both precision and foresight.

Cracking the Code: Hammer and Anvil

To crack open a nut, chimpanzees rely on a two-part tool system involving a hammerstone and an anvil. The hammerstone, gripped in hand, is used to strike nuts placed on the anvil, which must be stable and durable enough to withstand repeated impacts.

Plots of the average efficiency rank of rock combinations (hammer:anvil) through the course of the two portions of the experiment (Condition 1, Condition 2). The experiment is divided into a sequence of individual rock selections (defined as an instance where the hammer or anvil is changed) to investigate general patterns through the course of the experiment. Spearman's rank correlation is conducted on the efficiency rank value through the sequence of selections (see main text for Spearman's rank correlation values of rho). Credit: Journal of Human Evolution (2024). DOI: 10.1016/j.jhevol.2024.103625

For this study, researchers provided chimpanzees with premeasured rocks that varied in properties such as hardness, elasticity, weight, and size. They then observed how the apes selected and utilized these tools in their nut-cracking tasks.

Intentional Choices, Functional Results

The study revealed that chimpanzees prioritize functionality over appearance when selecting tools. They consistently chose harder stones for hammers, which are better suited to delivering forceful blows, and softer, more absorbent stones for anvils, which reduce the likelihood of the nut slipping off during the strike.

“Chimpanzees demonstrate an impressive understanding of material properties,” noted Dr. David Braun, one of the study’s authors. “Their choices are not arbitrary; they reflect a deep-seated practical intelligence that may parallel early hominin behaviors.”

What’s more, younger chimpanzees were observed using tools previously employed by older individuals in their groups. This behavior suggests that tool selection knowledge may be passed down socially, much like how early humans likely transmitted skills and techniques across generations.

Bridging Past and Present

The findings of this study underscore important similarities between the cognitive strategies of modern chimpanzees and ancient humans. Both groups seem to evaluate environmental materials with a focus on their functional potential.

“This research provides a fascinating window into the shared cognitive foundations of tool use,” said Dr. Susana Carvalho, a co-author of the paper. “It highlights how problem-solving and material selection have long been integral to survival for both apes and humans.”

These insights are particularly significant for understanding the evolution of toolmaking and the cognitive leaps that allowed early humans to refine their techniques. While humans have vastly advanced their technological capabilities, the shared behaviors between chimps and ancient hominins remind us of our common roots.

What’s Next?

This study opens the door to further investigations into the cognitive parallels between modern apes and early humans. Could similar learning processes and social dynamics underpin the evolution of tool use in other species? Researchers hope to expand this line of inquiry, examining tool selection in other highly intelligent animals and exploring how these behaviors evolved in response to environmental challenges.

Related Research

1. Toth, N., & Schick, K. (2009). "The Oldowan: The tool-making tradition of early hominins." Evolutionary Anthropology, 18(4), 159–171.
   DOI: 10.1002/evan.20235
   This study explores the significance of Oldowan tools in early human evolution and their role in shaping cognitive and social behaviors.

2. Boesch, C., & Tomasello, M. (1998). "Chimpanzee and human cultures." Current Anthropology, 39(5), 591–614.
   DOI: 10.1086/204785
   This paper examines cultural transmission in chimpanzees, offering insights into how knowledge of tool use might be passed down socially.

3. Panger, M. A., et al. (2002). "Tool use by wild capuchin monkeys." American Journal of Physical Anthropology, 119(1), 23–44.
   DOI: 10.1002/ajpa.10165
   Discusses parallels in tool use between primate species and what these behaviors reveal about the evolution of intelligence.

1. Braun, D. R., Carvalho, S., Kaplan, R. S., Beardmore-Herd, M., Plummer, T., Biro, D., & Matsuzawa, T. (2025). Stone selection by wild chimpanzees shares patterns with Oldowan hominins. Journal of Human Evolution, 199(103625), 103625. https://doi.org/10.1016/j.jhevol.2024.103625