Chimpanzee cultures are more complex than we realized

For decades, scientists have demonstrated that chimpanzees, like humans, pass complex cultural practices, such as tool use, from one generation to the next. 

However, while human culture has evolved dramatically – from the Stone Age to the Space Age – chimpanzee cultures appear relatively unchanged. 

This gap has long been attributed to humans’ unique ability to refine and build on cultural knowledge over time. Recent research suggests, however, that this distinction may not be as clear-cut as previously thought. 

A new interdisciplinary study led by the University of Zurich presents evidence that some of chimpanzees’ most complex behaviors may have been passed down and refined over generations, offering an early example of cumulative culture.

The history of chimpanzee culture

Chimpanzees often use tools made of perishable materials like sticks and stems, which leave little evidence for tracing their cultural evolution. 

“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,” explained lead author Cassandra Gunasekaram from the University of Zurich.

To overcome this limitation, the research team – comprising anthropologists, primatologists, physicists, and geneticists from universities in Zurich, St. Andrews, Barcelona, Cambridge, Konstanz, and Vienna – used genetic data to uncover historical links between chimpanzee populations. 

By combining genetic analysis with field data on foraging behaviors across 35 chimpanzee study sites in Africa, they unearthed clues about how cultural practices were transmitted and evolved over thousands of years.

Early stages of cumulative culture

The researchers classified chimpanzee foraging behaviors into three categories: those that required no tools, those using simple tools (e.g., leaf sponges to collect water), and the most complex practices that involved toolsets – a series of tools used sequentially to achieve a task.

One such toolset is employed by chimpanzees in the Congo region to extract termites. 

“Chimpanzees in the Congo region first use a strong stick to dig a deep tunnel through hard soil to reach an underground termite nest,” Gunasekaram explained. 

“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.”

Technologies transmitted across populations

A key finding of the study was that complex toolsets showed the strongest genetic links across distant populations. 

“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,” said corresponding author Andrea Migliano, a professor of evolutionary anthropology at the University of Zurich. 

“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.”

This finding supports the idea that complex behaviors were not independently developed in different regions but were instead passed down and spread through interconnected chimpanzee communities.

Female migrations and cultural transmission

In chimpanzee societies, females migrate to new communities upon reaching sexual maturity, helping to prevent inbreeding. 

According to the researchers, these migrations not only spread genetic diversity but may also have played a critical role in disseminating cultural innovations.

The study revealed that when both complex toolsets and their simpler components were found at different sites, genetic markers suggested that those sites were historically connected through female migrations. 

This pattern implies that more sophisticated toolsets were likely built incrementally by modifying simpler practices. 

“These groundbreaking discoveries provide a new way to demonstrate that chimpanzees have a cumulative culture, albeit at an early stage of development,” Migliano said.

A new perspective on chimpanzee culture

The study provides compelling evidence that chimpanzees possess a rudimentary form of cumulative culture. 

Although far less advanced than human cultural evolution, these findings challenge the assumption that cumulative culture is exclusive to humans. 

By tracing the genetic and cultural links between chimpanzee populations, the research highlights how generations of chimpanzees have passed down and refined behaviors, particularly their most complex tool-use practices.

This new understanding opens doors to further exploration of how cultural transmission occurs in other non-human species, potentially reshaping how we view the evolutionary origins of human culture.

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