Chimpanzees share knowledge just like humans, spurring innovation

Chimpanzees share knowledge just like humans, spurring innovation

Rachel Nuwer

Chimpanzees live in rigidly hierarchical social communities in which male members remain within the same group over time. To prevent inbreeding, females migrate to new communities when they reach adulthood. They bring with them not only new genes, but also new knowledge.

As this process repeated itself over thousands of years, female chimpanzees played an important role in promoting cultural innovation, according to a new study. Women spread behaviors across communities, and these behaviors were recombined with existing traditions to create layers of innovation that resulted in increasingly complex and sophisticated toolkits.

The new study shows that humans are not the only species capable of innovating over time to make them more efficient, says Cassandra Gunasekaram, a doctoral student in evolutionary biology at the University of Zurich and lead author of the study published in the journal Science. In addition, she said, the study demonstrates “the importance of social connections between different chimpanzee populations in increasing cultural complexity.”

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Back in the 1990s, the idea that non-human animals could exhibit distinct, socially learned behaviors that constitute culture was controversial. Numerous examples of animal culture are now known, including various dialects of birdsong, whale vocalizations, and the “wag dance” of honey bees.

However, a new paper on chimpanzees shows an example of cumulative culture that is different from others. Cumulative culture refers to knowledge that is passed down from generation to generation, allowing the development of increasingly complex new technologies resulting from the gradual accumulation of new ideas and breakthroughs contributed by many minds. Cumulative culture products are usually so complex that it would be virtually impossible for one person to invent them. Computers are an example: they became more complex and efficient as researchers iterated and developed what came before, to the point that no one could build a computer to today’s standards entirely from scratch.

Cumulative culture is still primarily considered a feature of human society. However, some researchers have begun to question this assumption, and recent research confirms that cumulative culture can be found in some other species. Like humans, chimpanzees appear to have the ability to exchange and combine ideas, says study co-author Andrea Migliano, an evolutionary anthropologist at the University of Zurich. However, she adds that the amount of cultural knowledge animals can accumulate is limited by their hierarchical social structure, limited migration between groups, and lack of spoken language.

To conduct the new study, Migliano, Gunasekaram and their colleagues turned to an existing open dataset maintained by the Pan African Program, a chimpanzee research consortium. They used genetic data from 240 individual chimpanzees from 35 different communities, representing all four subspecies, to trace past encounters between the animals. First, the researchers reconstructed a 5,000-year family tree by analyzing segments of DNA that pointed to common relatives and were broken down into smaller pieces over different generations. They then traced the connections between populations over 15,000 years, tracking genetic variants that were common in some groups but rare in others.

In addition to the genetic analysis, they also mapped 15 feeding behaviors across chimpanzee populations. They divided the behavior into three categories: the simplest behavior does not require the use of tools; intermediate examples were based on one tool; and the most complex of them depended on a complex set of tools. An example of a complex tool kit involved a multi-step approach to accessing hives inside trees, using various tools to open the hive, enter the inner chamber, and collect honey for collection.

Finally, the researchers overlaid and compared these networks of findings—genetic relatedness and cultural similarity—to see whether one predicted the other, providing possible support for cumulative culture. When the simplest behaviors were included, they found no corresponding evidence of genetic exchange between groups. However, when only the most complex behaviors were analyzed, they found a clear correlation with female migration. This suggests that women moving into a new group play a role in driving innovation and is consistent with the hypothesis that social transmission between groups is necessary to develop only the most complex tools rather than simpler ones, Migliano says. “The main pattern we see is that if it is complex, then it really correlates with migration and is unlikely to be reinvented,” she adds.

“This project provides the best evidence yet that wild chimpanzee traditions are indeed cultural and that they can and have evolved cumulatively,” says Thomas Morgan, an evolutionary anthropologist at Arizona State University who was not involved in the work. “The idea that cumulative cultural change is the secret of our species has emerged over the last few decades, but recent work, including this project, is really changing that view.”