Chimps Caught Sharing Boozy Fruit Feasts

In a remote corner of Guinea-Bissau’s Cantanhez National Park, wild chimpanzees are engaging in behavior that might feel oddly familiar to humans: sharing alcoholic treats with friends and family. For the first time, researchers have documented wild chimpanzees repeatedly eating and sharing naturally fermented African breadfruit containing measurable amounts of ethanol—what we commonly call alcohol.

The groundbreaking footage, captured by motion-activated cameras set up by University of Exeter researchers, shows chimps passing around fermented fruits on ten separate occasions, raising intriguing questions about the evolutionary roots of human alcohol consumption and social feasting traditions.

“For humans, we know that drinking alcohol leads to a release of dopamine and endorphins, and resulting feelings of happiness and relaxation,” said Anna Bowland from the Centre for Ecology and Conservation at Exeter’s Penryn Campus in Cornwall. “We also know that sharing alcohol—including through traditions such as feasting—helps to form and strengthen social bonds.”

This unexpected discovery has researchers wondering: “Could they be getting similar benefits?” Bowland asks.

The research team measured the ethanol content of the fruits using a portable breathalyzer during their field study from April to July 2022. They found that 86% of sampled fruits contained alcohol, with levels ranging from 0.01% to 0.61% ABV (Alcohol By Volume). While these concentrations might seem modest compared to human alcoholic beverages, they could add up significantly considering that fruit comprises 60-85% of a chimpanzee’s diet.

Interestingly, the “late ripe” fruits—those with softer exteriors that had changed from deep green to yellow with a spongy pulp texture—contained the highest average ethanol concentration at 0.26%. These more fermented fruits were shared in half of the documented sharing events.

The footage reveals that sharing typically occurred without conflict. In seven of the ten observed instances, chimps shared fruits even when other non-monopolized fruits were available nearby. In two documented cases, the chimps bypassed less fermented fruits in favor of sharing the more fermented ones.

Dr. Kimberley Hockings, another researcher from the University of Exeter involved in the study, noted the significance of this selective sharing. “Chimps don’t share food all the time, so this behavior with fermented fruit might be important,” she said. “We need to find out more about whether they deliberately seek out ethanolic fruits and how they metabolise it, but this behavior could be the early evolutionary stages of ‘feasting’.”

The research adds to growing evidence that human alcohol consumption may have deeper evolutionary roots than previously thought. A molecular adaptation that significantly increased ethanol metabolism was discovered in the common ancestor of African apes, suggesting that incorporating fermented foods in diets may have ancient origins for both humans and chimpanzees.

Beyond the social aspects, there might be practical reasons why chimpanzees would favor fermented fruits. As fruits ferment, their chemical and mechanical defenses break down, making them easier to access and reducing the energy needed to consume them. The researchers observed that chimpanzees needed considerable force to access less fermented breadfruits, which was never necessary with the riper, more fermented specimens.

Fermentation also increases the vitamin content of foods, potentially making these fruits nutritionally valuable despite—or perhaps because of—their alcohol content. Combined with their relative rarity and large size, these benefits might make fermented breadfruits particularly worthy of sharing among chimpanzee communities.

The researchers stress that the chimpanzees are unlikely to become intoxicated from consuming these fruits—which would clearly be detrimental to their survival in the wild. However, the social context of sharing these special foods might echo the human tradition of communal feasting.

“If so, it suggests the human tradition of feasting may have its origins deep in our evolutionary history,” Hockings observed.

While the current data provides fascinating initial insights, the researchers acknowledge that more investigation is needed to fully understand the phenomenon. Future research will require long-term observations of individuals with established relationships to monitor changes in feeding and social behavior, alongside continued measurements of ethanol in various foods consumed by wild great apes.

The study, recently published in the journal Current Biology, represents another remarkable example of how our closest evolutionary relatives continue to surprise us with behaviors that mirror our own in unexpected ways. From tool use to political maneuvering, and now possibly social drinking, chimpanzees offer us a window into our shared evolutionary past—and perhaps even the origins of some distinctly human cultural practices.

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