A new study suggests that wild chimpanzees consume the equivalent of several daily drinks, supporting the idea that our appetite for booze is an ancient evolutionary trait.
The sun is dipping low over the canopy of Ngogo in Uganda’s Kibale National Park. For Porthos, a high-ranking male chimpanzee, the day ends as it often begins: with a feast. He is perched in a giant fig tree, plucking the sticky, overripe fruit. It’s sweet and soft, and, thanks to the yeast breaking down the sugars inside, it’s slightly boozy.
It’s not just dinner; it’s a daily ritual for Porthos and his entire community, one that researchers now believe provides a missing link in the story of human alcohol consumption.
For decades, the idea that our primate ancestors frequently consumed alcohol was met with skepticism. Primatologists argued that apes wouldn’t eat fruit fermented enough to contain ethanol. But a new study, published in Science Advances, has overturned that assumption. The study systematically measured the alcohol content of fruit in the wild.
The findings, led by researchers at the University of California, Berkeley, suggest that far from being a rare treat, low-level alcohol consumption is a chronic part of the wild ape diet.
The Equivalent of 2.5 Daily Drinks
To understand the chimp’s “daily buzz,” researchers first had to sample their menu. By collecting undamaged, freshly fallen fruit from the ground—the fruit the chimps were eating—they could measure the ethanol content in over 21 species at sites in Uganda and the Ivory Coast.
The results were striking:
- Daily Dose: On average, male and female chimpanzees consume about 14 grams of pure ethanol daily.
- Human Equivalent: When adjusted for body mass, a chimpanzee weighs around 40 kg compared to a typical 70 kg human. This intake is the equivalent of consuming roughly 2.5 standard human alcoholic drinks daily.
While the fruits contained a low alcohol percentage (around 0.26% by weight), the sheer volume consumed daily—chimps eat 5 to 10 percent of their body weight in fruit—adds up to a substantial daily dosage. Critically, because this consumption is spread throughout the day, the chimps do not appear to get intoxicated.
The Drunken Monkey Hypothesis
The research provides the strongest evidence yet for biologist Robert Dudley’s original two-decade-old proposal of the “drunken monkey” hypothesis.
The hypothesis argues that the human appetite for alcohol is not a modern vice but a survival trait inherited from our primate ancestors. Due to its advanced ripeness, fermented fruit is easier to digest and offers higher caloric rewards. Primates with a genetic disposition to seek out and tolerate low levels of ethanol would have been more successful at finding energy-rich food sources.
Our evolutionary path suggests that the ability to metabolize alcohol and the attraction to its sweet, fermenting odor were deeply rooted adaptations shared by the last common ancestor of humans and apes, potentially 13 million years ago.
From Fruit Find to Social Lubricant
The study’s implications extend beyond simple biology and into social behavior. The researchers noted that the most popular fruits—like the fig Ficus musuco—had the highest alcohol content. At the Ngogo site, male chimpanzees often gather in these fig trees to consume the fruit before embarking on risky activities like boundary patrols.
While speculative, the findings open a tantalizing question: Could the low-level, chronic exposure to alcohol from these fruits be a social lubricant, reducing tension, or perhaps even giving the chimps a small measure of “courage” before a dangerous encounter?
Regardless of the social function, the research confirms that our attraction to alcohol has a deep evolutionary background. Therefore, when we reach for that beer or glass of wine, we echo the dietary preferences of Porthos and our primate ancestors.
