Leo Sands
You don’t have to venture far to observe humans in the wild sharing a few drinks at mealtimes. But we’re not the only ones.
For the first time, wild chimps have been recorded indulging in alcohol together. (Just swap out the bottle of wine for a volleyball-size fermented breadfruit.)
According to the scientists who documented the scenes on video, the behaviour opens up the possibility that the primates – humans’ closest relatives in the animal kingdom – could also use booze as a social bonding tool.
The ecologists at England’s University of Exeter say they believe the sharing of boozy food is likely to be widespread among chimpanzees – and has probably been observed previously without researchers realizing what they were seeing. The exact reason chimps share the alcohol-laced breadfruit for consumption is not yet known.
Still, the peer-reviewed findings, published in the journal Current Biology on Monday, offer a clue to another mystery: the origins of alcohol-fueled feasting in humans, raising the idea that this trait is not a recent development but deeply rooted in our shared evolutionary history with other great apes. Researchers have long suspected that humans’ ability to metabolize alcohol could serve an evolutionary purpose – a theory known as the drunken monkey hypothesis.
Using hidden cameras planted in Guinea-Bissau’s Cantanhez Forests National Park, in western Africa, researchers recorded wild chimpanzees sharing breadfruits containing ethanol on 10 occasions – most of the time passively, by allowing another chimp to snatch a breadfruit in their possession, a form of sharing. In one instance caught on camera, a chimpanzee tolerated a fermented breadfruit being snatched directly from its mouth.
Both the sharing of food and consumption of alcohol by wild chimpanzees have been observed previously – but never at the same time.
“We suspect that this isn’t a rare occurrence and that actually the sharing of fruit that have a level of alcohol is probably relatively widespread,” Anna Bowland, the University of Exeter ecologist who led the study, said in a phone interview.
Bowland and her team measured the breadfruit’s alcohol-by-volume content, finding that it ranged from 0.01 to 0.61 percent. Although that might seem low (a typical beer has an ABV of about 5 percent), she said it could still add up when consumed in large quantities. “What you have to remember is that for chimpanzees, 60 to 85 percent of their diet is fruit. So if all the fruit contains even small amounts of alcohol, it might turn out to be significant,” Bowland said.
Chimpanzees have been documented to share a remarkable number of behaviors and characteristics with humans, including exhibiting unique conversational patterns, remembering old friends decades later, consoling victims of aggression and even going through menopause.
Like humans, chimpanzees have evolved to possess a pair of enzymes that allow them to convert ethanol into sugar, thereby giving them the ability to consume alcohol.
The reason for this trait remains unclear. According to researchers, there are several possible benefits for humans and apes to feast on alcohol collectively, including nutritional and social ones.
“Sharing is linked to social bonding, but also alcohol intake is linked to social bonding – at least in humans,” Bowland said. “So it would be interesting to know whether the natural levels that chimpanzees are feeding on are having a social impact.” The scientists did not track behavioral changes in the chimps, so they could not determine whether they seemed drunk, and more research needs to be done, she said.
According to Robin Dunbar, an evolutionary psychologist at the University of Oxford who was not involved in the study, the reason chimps might share alcohol is unknown – but there could be a social benefit.
In humans, he said in a phone interview, alcohol can activate the brain’s endorphin system, functioning as a kind of “social glue” that fosters a sense of belonging when consumed in a group setting.
It’s not entirely clear whether the chimpanzees were getting the same social benefit, he said: “They’re exchanging among themselves dollops of fermented mush. But it’s not clear what the psychobiological consequences of that would be. Are they getting the same feelings that we get from drinking out? And in particular, the kind of bonhomie sense you get when you’re out having a few beers with your buddies, as it were?”
Dunbar also noted that while the sharing of meat has been frequently observed among chimpanzees, it is rarer for vegetable matter – making the breadfruit feasts notable.
The observation of chimpanzees sharing alcohol could also shed light on another mystery: When did the social consumption of alcohol by humans originate? The archaeological record of human alcohol consumption stretches back only about 10,000 years, Dunbar said – and so may never provide a definitive answer.
The observation of alcohol consumption in chimps could be a rare indication that humans’ relationship with alcohol dates back to our predecessors millions of years ago – when we last shared a common ancestor with chimpanzees.
“If chimpanzees do it and humans do it – and they are our nearest relatives – then the likelihood is, everybody in between did it, too. It’s much less likely that two closely related genera have evolved a capacity – even if it’s only a behavioral thing – independently of each other,” Dunbar said. “It’s much more likely that it’s a common ancestral trait.”
