When you picture chimpanzees in the wild, chances are you imagine them swinging through trees or munching on figs – not sipping on a “beer.” Yet new research suggests that chimps in Uganda and Ivory Coast (Africa) are naturally consuming the alcoholic equivalent of half a pint of lager every day. Their diet, rich in ripe and fermented fruit, inadvertently delivers enough ethanol to match the intake of a standard U.S. drink. This surprising discovery not only sheds light on primate feeding habits but also supports the intriguing “drunken monkey” hypothesis, which links human attraction to alcohol to our evolutionary past.
The study, conducted in Kibale National Park in Uganda and Taï National Park in Ivory Coast, measured ethanol levels in fallen fruit commonly consumed by wild chimpanzees. While the alcohol content of individual fruits was relatively low – less than 0.5% – the sheer volume of ripe fruit consumed by the apes translated into a significant daily intake.
On average, chimps eat 5–10% of their body weight in fruit daily, working through around 4.5 kilograms. That means even low ethanol concentrations add up to about 14 grams of pure alcohol per day. For comparison, that’s equivalent to one standard U.S. drink or half a pint of 5% ABV beer.
The research highlighted that chimpanzees are particularly fond of figs, a fruit that tends to have higher natural alcohol levels once fermented. By feasting on ripe fruit pulp, they end up unintentionally “drinking” while feeding. Importantly, despite their alcohol intake, the chimps do not appear visibly intoxicated. Researchers noted that the amount of fruit required to actually cause drunkenness would likely leave the apes too bloated to keep eating.
The findings lend strong support to the “drunken monkey” hypothesis proposed by Professor Robert Dudley of UC Berkeley. According to this theory, the human tendency to consume alcohol may be rooted in evolutionary history, where primates – including our ancestors – were naturally drawn to energy-rich, fermented fruit. This dietary heritage could explain why humans developed both a taste for and a tolerance of alcohol.
Graduate student Aleksey Maro, part of the study team, suggests that this evolutionary link means our attraction to alcohol is not purely cultural but biologically inherited.
Chimpanzees are far from the only animals with a taste for booze. In 2015, researchers observed a troop of chimps in Guinea (Africa) engaging in habitual drinking sessions, sometimes starting as early as dawn. Footage has even shown chimps bonding over fermented breadfruit.
Beyond primates, other species have also been caught indulging. A review published last year found that alcohol consumption is surprisingly widespread in the animal kingdom. The slow loris, for example, is known to guzzle potent alcoholic nectar. What might seem like “drunken” behavior in animals often has deep evolutionary roots.
For humans, the NHS recommends consuming no more than 14 units of alcohol a week - equivalent to around 112 grams of pure alcohol. Chimps, meanwhile, are ingesting about 98 grams per week, putting them surprisingly close to human health guidelines. However, unlike humans, chimps show little evidence of intoxication, suggesting their bodies may process ethanol differently.
Still, it’s worth noting that recent studies emphasize there is no safe level of alcohol consumption for humans, linking even small amounts to long-term health risks.
The discovery that wild chimpanzees consume the equivalent of a beer a day without showing signs of drunkenness offers fascinating insights into both animal behavior and human evolution. By gorging on ripe, fermented fruits, chimps inadvertently take in alcohol – an ancient dietary trait that may explain why humans have an enduring relationship with alcohol today. The research not only reinforces the “drunken monkey” hypothesis but also highlights how our shared evolutionary past continues to shape modern habits.
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