Chimpanzees pass down what they’ve learned, much like humans

Human culture and society are based on the idea of learning new things and teaching new generations how to do those things. But this approach, called cumulative culture, may not be unique to humans. According to a new study, chimps do the same thing.

Chimps cracking nuts. Image credits: Koops et al (2022).

Chimps don’t automatically know what to do when they come across nuts and stones. That simple bit of information may not seem like much on its own, but it actually says a lot about how they develop and pass knowledge.

Some groups of chimpanzees in Guinea have figured out that they can use tools to crack nuts; others have not. Researchers wanted to see whether other chimps can individually figure out how nut-cracking works, or if this knowledge is passed on in the group that figured it out. If this were indeed the case, it would mean that passing information is embedded into chimpanzee culture, much like it is embedded in human culture.

To get to the bottom of this, a team led by primatologist Kathelijne Koops from Zurich University set up an experiment where they exposed another chimpanzee group just 6 km away from a tool-using group to everything it needed to crack open nuts — they even provided them with palm nuts.

Initially, the chimps were excited by the stone tools. But they didn’t figure out how to crack the nuts, and over a few months, they gradually lost interest. The researchers then added a palm fruit to the experimental setup, to familiarize the chimps with the food source. They even cracked open some nuts and placed them on top of the stone tools, to give them a hint, and offered some easier-to-crack types of nuts.

But regardless of what they did, they couldn’t get the chimps to crack open the nuts without being shown how to do it.

Image credits: Koops et al (2022).

“None of the Seringbara chimpanzees cracked nuts, nor attempted to do so. Hence, stimulus/local enhancement (nuts and stones) or end-state emulation (cracked-open nuts) did not elicit a nut-cracking (re-)innovation in these wild chimpanzees,” the researchers write in the study. “In sum, nut cracking was not independently (re-)innovated by wild Western chimpanzees in field experiments.”

This strongly suggests that cracking nuts is a behavior chimps teach among their group, much like humans do. It’s a form of social learning that allowed human culture to develop progressively more complex tools and technologies. This new finding would force us to re-think how unique human culture really is.

“Our findings suggest that chimpanzees acquire cultural behaviors more like humans and do not simply invent a complex tool use behavior like nut cracking on their own,” says Koops. “Our findings on wild chimpanzees, our closest living relatives, help to shed light on what it is (and isn’t!) that makes human culture unique. Specifically, they suggest greater continuity between chimpanzee and human cultural evolution than is normally assumed and that the human capacity for cumulative culture may have a shared evolutionary origin with chimpanzees.”

Previous experiments have suggested that captive primates can start using tools without being taught, but some researchers suspected that this may be because they observed humans using tools and learned this behavior from them. This new experiment seems to suggest this idea is true.

If humans and chimpanzees both exhibit cumulative culture, and since the two species are so closely related biologically, it’s plausible that cumulative culture was also a trait of our common ancestor with chimpanzees.

“Our findings suggest greater continuity between chimpanzee and human cultural evolution than is normally assumed,” the researchers conclude.

The study was published in Nature Human Behavior.

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