Chimpanzees capture sharing fanatic fruit feast

In a remote corner of Cantanhez National Park in Guinea-Bissau, wild chimpanzees are engaged in behaviors that humans may feel strange: sharing an alcoholic diet with friends and family. For the first time, researchers documented wild chimpanzees, repeatedly eating and sharing naturally fermented African breadfruits containing measurable amounts of ethanol, commonly known as alcohol.

A groundbreaking footage captured by a motion-activated camera set up by University of Exeter researchers shows chimpanzees bypassing fermented fruits on ten different occasions, raising interesting questions about the evolutionary roots of human alcohol consumption and the grand traditions of society.

“For humans, we know that drinking alcohol causes the release of dopamine and endorphins and brings a sense of happiness and relaxation,” said Anna Bowland of the Ecology and Conservation Center on the Penryn campus in Exeter, Cornwall. “We also know that sharing alcohol (including feasts), including foam-flux, forms and strengthens social bonds.”

This unexpected discovery made the researchers wonder: “Can they get similar benefits?” Bao Lan asked.

The team measured the ethanol content of the fruit during the on-site study using a portable breath analyzer between April and July 2022. They found that 86% of the sampled fruits contained alcohol, with levels ranging from 0.01% to 0.61% (the amount of alcohol). Although these concentrations appear to be significant compared to human alcoholic beverages, the fruit accounts for 60-85% of the chimpanzee diet.

Interestingly, “late-ripe” fruits – those with softer exteriors, which change from dark green to yellow, spongy flesh texture changes with the highest average ethanol concentration of 0.26%. These more fermented fruits are shared in half of recorded sharing events.

Video shows that sharing usually does not conflict. In seven of the ten observed instances, chimpanzees shared fruits even if other non-selling fruits were nearby. In two recorded cases, chimpanzees bypassed less fermented fruits and instead shared more fermented fruits.

Another researcher at the University of Exeter, Dr. Kimberley Hockings, pointed out the significance of this selective sharing. “Chimps don’t always share food, so the behavior of this fermented fruit may be important,” she said. “We need to learn more about whether they deliberately look for ethanol fruits and how they metabolize, but this behavior may be an early evolutionary stage of “cooking.”

This study adds to growing evidence that human drinking may have deeper evolutionary roots than previously thought. A molecular adaptation was found in the common ancestor of African apes, significantly increasing ethanol metabolism, suggesting that incorporating fermented food into the diet may have ancient origins in humans and chimpanzees.

In addition to social aspects, chimpanzees prefer fermented fruits to be the actual reasons. As the fruits ferment, their chemical and mechanical defense capabilities break down, making them easier to acquire and reduce the energy they consume. The researchers observed that chimpanzees need considerable strength to obtain less fermented breadfruit, which is never necessary for mature, more fermented specimens.

Fermentation also increases the vitamin content of foods, which may still make these fruits nutritious, although or possibly due to their alcohol content. Combined with its relative rarity and large size, these benefits may make fermented breadfruit particularly worth sharing in the chimpanzee community.

The researchers stress that chimpanzees are unlikely to be intoxicated by eating these fruits, which is obviously not conducive to their survival in the wild. However, sharing the social context of these special foods may echo the human tradition of public feasts.

“If so, it shows that the human tradition of feasts may have originated in our evolutionary history,” Hawkins observed.

While the current data provide engaging initial insights, the researchers acknowledge that more research 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, as well as continuous measurement of ethanol in a variety of foods consumed by wild giant apes.

The study, recently published in the journal Current Biology, represents another remarkable example of how our closest evolutionary relatives continue to surprise us in unexpected ways in which we behave. From tools to political maneuvers, and perhaps even social drinking, chimpanzees provide us with a window into our shared evolutionary past, and perhaps even the origins of some obvious human cultural practices.

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