Like humans, chimpanzees pass on complex cultures, such as tool use, from generation to generation. Human culture has evolved significantly from the Stone Age to the Space Age, driven by continuous advancements.
In contrast, chimpanzee cultures have not undergone similar changes, indicating that only humans possess the unique ability to develop increasingly complex cultures over time.
Scientists studying wild chimpanzees have challenged the idea that their culture remains static, suggesting that some of their complex behaviors, like using multiple tools in sequence to extract food, may have developed over time. A new study by the University of Zurich proposes that these advanced behaviors could be passed down and refined across generations.
Lead author Cassandra Gunasekaram from the Department of Evolutionary Anthropology at the University of Zurich said, “As most chimpanzee tools, such as sticks and stems, are perishable, there are few records of their history to confirm this hypothesis—unlike human cases such as the evolution of the wheel or computer technology.”
The new study involved anthropologists, primatologists, physicists, and geneticists from institutions in Zurich, St. Andrews, Barcelona, Cambridge, Konstanz, and Vienna. They collaborated to trace genetic links between chimpanzee populations over thousands of years, using groundbreaking genetic discoveries to uncover aspects of chimpanzee cultural history in previously unimaginable ways.
The authors gathered genetic data from 35 chimpanzee study sites across Africa to identify genetic similarities between groups. They also compiled information on foraging behaviors, categorizing them into three types: behaviors requiring no tools, simple tools (like using a leaf sponge to collect water), and the most complex behaviors involving a toolset.
Gunasekaram said, “As an example of such a toolset, chimpanzees in the Congo region first use a strong stick to dig a deep tunnel through hard soil to reach an underground termite nest. Next, they make a ‘fishing’ probe by pulling a long plant stem through their teeth to form a brush-like tip, pressing it into a point, and deftly threading it down the tunnel they’ve made. They then pull it out and nibble off any defending termites that have bitten into it.”
Corresponding author Andrea Migliano, professor of evolutionary anthropology at UZH, said, “We made the surprising discovery that it is the most complex chimpanzee technologies—the use of entire ‘toolsets’—that are most strongly linked across now distant populations.”
“This is exactly what would be predicted if these more advanced technologies were rarely invented and even less likely to be reinvented, and therefore more likely to have been transmitted between groups.”
The study found that sexually maturing female chimpanzees, who migrate to new communities to prevent inbreeding, play a key role in spreading genes and potentially cultural advances between neighboring groups over time.
The research revealed that genetic markers showed a historical connection between these sites via female migrations when both complex and simpler toolsets were present at different sites. This suggests that the more complex tool behaviors developed gradually by building upon or modifying simpler ones.
Migliano said, “These groundbreaking discoveries provide a new way to demonstrate that chimpanzees have a cumulative culture, albeit at an early stage of development.”
Journal Reference:
- Cassandra Gunasekaram et al., Population connectivity shapes the distribution and complexity of chimpanzee cumulative culture, Science (2024). DOI: 10.1126/science.adk3381