In the lush canopies of Guinea-Bissau’s Cantanhez National Park, a group of wild chimpanzees has been caught in a moment that’s oddly familiar: eating and sharing fruit laced with alcohol.

For the first time, researchers have filmed chimpanzees in the wild sharing fermented African breadfruit, which contains ethanol. The footage was gathered over months using motion-activated cameras and captures something quintessentially human: sharing a mild buzz with the boys.

A Primate’s Toast

The scientists from the University of Exeter in the UK documented ten separate instances of chimps consuming the naturally fermented fruit. Tests revealed the alcohol content reached as high as 0.61% ABV — less than a weak beer, but still enough to raise eyebrows.

Like humans, chimps have a taste for alcohol. In 2015, for instance, researchers spotted wild chimps guzzling wine not once, not twice, but 51 times over the course of a 17-year study in the village of Bossou in Guinea. The chimps seek out raffia palms, a plant that produces a tree sap that naturally ferments into wine. Villagers in Bossou traditionally leave containers out in the morning at the crown of the trees for the sap to drip into throughout the day.

However, what fascinates the researchers of the new study isn’t the consumption behavior itself. The chimpanzees didn’t just eat the intoxicating fruit. They shared it.

“Chimps don’t share food all the time, so this behaviour with fermented fruit might be important,” said Dr. Kimberley Hockings, a primatologist at the University of Exeter. “We need to find out more about whether they deliberately seek out ethanolic fruits and how they metabolise it, but this behaviour could be the early evolutionary stages of ‘feasting’.”

That’s an interesting thought that might be more consequential than it meets the eye. If these gatherings over mildly alcoholic fruit represent a kind of proto-feast, they may echo deep evolutionary roots. It could suggest that our own social rituals involving alcohol could trace back millions of years.

An Ancient Tradition?

The idea that early humans evolved alongside — and sometimes thanks to — the presence of ethanol in ripe and fermented fruits isn’t new. The “drunken monkey hypothesis,” proposed by biologist Robert Dudley, suggests that our primate ancestors may have developed a taste for ethanol-rich fruit, and with it, the ability to metabolize alcohol.

That adaptation may not be exclusive to us. “Recent discoveries of a molecular adaptation that greatly increased ethanol metabolism in the common ancestor of African apes suggests eating fermented fruits may have ancient origins in species including humans and chimps,” the researchers noted.

“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 of Exeter’s Centre for Ecology and Conservation. “We also know that sharing alcohol — including through traditions such as feasting — helps to form and strengthen social bonds.”

So, could chimpanzees be feeling something similar?

It’s a difficult question to answer definitively. The researchers stress that the alcohol levels found in the fruit are relatively low, and chimps aren’t likely to get drunk in the way humans do. Intoxication, after all, doesn’t lend itself well to survival in the wild.

Still, given that fruit makes up 60–85% of a chimpanzee’s diet, even small amounts of ethanol could accumulate. What’s more, if chimps are choosing fermented fruit over fresh alternatives — and sharing it — they may be doing more than just foraging. They may be bonding.

A Forest Cocktail Party

The discovery blurs yet another line between humans and our closest living relatives. It hints at the possibility that some of the social behaviors we think of as uniquely human — sharing drinks, holding feasts, forming rituals around food — are much more ancient than we thought. They might originate in the treetops of West Africa.

It also raises new questions. Do chimps actively seek out fermented fruit? Do they feel the effects? Could their brains, like ours, respond to ethanol with a dose of pleasure?

For now, these remain open mysteries. But one thing is clear: the seeds of our own evolutionary story are still bearing fruit — sometimes fermented, and sometimes shared — in the forests where our cousins live.

The findings appeared in the journal Current Biology.