Main image: Chimpanzee next to a tree. Photo: Guerrero De la Luz Pexels
Deep in the forests of Guinea-Bissau on the African continent, researchers caught wild chimpanzees doing something unexpectedly familiar: they shared fruit. It was not just any fruit, but naturally fermented fruit containing alcohol.
In a new study published in Current Biology, scientists observed chimps in Cantanhez National Park munching on African breadfruit that had begun to ferment. What caught researchers’ attention was not just that the chimps ate the fruit but shared it, suggesting there is more going on than just snacking.
“Chimps don’t usually share food unless there’s a strong reason,” says Dr Kimberley Hockings, one of the study’s co-authors from the University of Exeter. That is what makes these findings so intriguing. It hints that the chimps may find some reward, not just from the taste of the fruit but from sharing it.
Using motion-triggered cameras, researchers recorded 10 occasions where chimpanzees consumed this fermented breadfruit. Lab tests confirmed that the fruit contained ethanol, with alcohol levels as high as 0.61% ABV (Alcohol By Volume – a measure used in alcoholic drinks). It may be low, but 60-85% of chimps’ diet is fruit, so low alcohol levels could add up to significant consumption. Researchers suggested chimps are unlikely to get “drunk”. It would not benefit their survival chances.
While the effects of alcohol on chimpanzee metabolism remain unclear, recent findings point to a molecular adaptation in the common ancestor of African apes that significantly boosted ethanol processing, hinting that the consumption of fermented fruit could have deep evolutionary roots shared by both humans and chimps.
It is not the first time researchers have captured chimps experimenting with alcohol. In a study published in 2017, chimpanzees showed interest in fermented nectar or even palm wine. What makes this latest discovery stand out is the social side of it.
If all of this is starting to sound a little human, you’re not alone. Alcohol plays a role in some social settings amongst humans, too, whether it is a celebration, a casual gathering, or even ancient rituals.
This behaviour lines up with something scientists call the “drunken monkey hypothesis.” The basic idea is that ripe, fermenting fruit drew our ancestors because it was richer in calories and easier to spot. Over time, this attraction might have laid the groundwork for modern human behaviours involving alcohol.
Interestingly, earlier genetic studies found that African great apes (chimps included) evolved a more efficient way to break down ethanol. So this fruit sharing might not just be an isolated curiosity; it could be a glimpse into something deeper, something that connects us.
Despite the alcohol content, researchers did not see obvious signs of intoxication. But that doesn’t mean the ethanol had no effect. In humans, even small amounts of alcohol can release feel-good chemicals like dopamine and endorphins, fostering feelings of closeness and relaxation. Chimps may experience something similar. Their fruit-sharing habit might serve a social purpose that’s surprisingly close to our own.
The study raises fascinating questions: Do chimps actively seek out fermented fruit? Do they prefer it to unfermented options? And what does this mean for how we think about our own relationship with alcohol? Further observations could help answer these questions and reveal just how deep the roots of our social drinking culture go.
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