Sep 18, 2025 04:20 AM
In the wild, chimps likely ingest the equivalent of several alcoholic drinks every day
https://news.berkeley.edu/2025/09/17/in-...every-day/
EXCERPTS: The first-ever measurements of the ethanol content of fruits available to chimpanzees in their native African habitat show that the animals could easily consume the equivalent of more than two standard alcoholic drinks each day, according to researchers at the University of California, Berkeley.
It’s not clear whether they actively seek out fruit with high ethanol levels, which are typically riper fruit with more sugars to ferment. But the availability of ethanol in many species of fruit that they normally eat suggests that alcohol is a regular part of their diet and likely was a part of the diets of our human ancestors.
“Across all sites, male and female chimpanzees are consuming about 14 grams of pure ethanol per day in their diet, which is the equivalent to one standard American drink,” said UC Berkeley graduate student Aleksey Maro of the Department of Integrative Biology. “When you adjust for body mass, because chimps weigh about 40 kilos versus a typical human at 70 kilos, it goes up to nearly two drinks.”
A “standard drink” in the U.S. contains 14 grams of ethanol, irrespective of the consumer’s body size, although in much of Europe the standard is 10 grams.
[...] “The chimps are eating 5 to 10% of their body weight a day in ripe fruit, so even low concentrations yield a high daily total — a substantial dosage of alcohol,” said Robert Dudley, UC Berkeley professor of integrative biology. “If the chimps are randomly sampling ripe fruit as did Aleksey, then that’s going to be their average consumption rate, independent of any preference for ethanol. But if they are preferring riper and/or more sugar-rich fruits, then this is a conservative lower limit for the likely rate of ethanol ingestion.”
[...] Dudley first began to suspect more than 20 years ago that the human appetite for alcohol was inherited from our primate ancestors, and wrote a 2014 book about his theory: The Drunken Monkey: Why We Drink and Abuse Alcohol. This “drunken monkey” hypothesis drew skepticism from many scientists — particularly those who study primates — who told him that chimps and other primates don’t eat fermented fruit or nectar. These nutrients typically contain alcohol produced by yeast metabolizing sugar, just as yeast ferments sugary grape juice into wine.
But over the years, Dudley’s theory has gained an increasing number of adherents. More primatologists now report seeing monkeys and apes eating fermented fruit, a practice that was recorded earlier this year among chimps in Guinea-Bissau. Researchers also have published papers about captive primates’ preferences for alcohol. Dartmouth University researchers in 2016 reported that when captive aye-ayes and slow lorises were offered nectar with varying percentages of alcohol, they finished off nectar with the highest alcohol content first — and then repeatedly revisited the empty high-alcohol containers as if they wanted more. In 2022, Dudley collaborated with researchers in Panama to document that spider monkeys consume alcohol-laden fermented fruit in the wild and express alcohol metabolites in their urine... (MORE - missing details, no ads)
https://youtu.be/rRgrxku64H4
https://www.youtube-nocookie.com/embed/rRgrxku64H4
https://news.berkeley.edu/2025/09/17/in-...every-day/
EXCERPTS: The first-ever measurements of the ethanol content of fruits available to chimpanzees in their native African habitat show that the animals could easily consume the equivalent of more than two standard alcoholic drinks each day, according to researchers at the University of California, Berkeley.
It’s not clear whether they actively seek out fruit with high ethanol levels, which are typically riper fruit with more sugars to ferment. But the availability of ethanol in many species of fruit that they normally eat suggests that alcohol is a regular part of their diet and likely was a part of the diets of our human ancestors.
“Across all sites, male and female chimpanzees are consuming about 14 grams of pure ethanol per day in their diet, which is the equivalent to one standard American drink,” said UC Berkeley graduate student Aleksey Maro of the Department of Integrative Biology. “When you adjust for body mass, because chimps weigh about 40 kilos versus a typical human at 70 kilos, it goes up to nearly two drinks.”
A “standard drink” in the U.S. contains 14 grams of ethanol, irrespective of the consumer’s body size, although in much of Europe the standard is 10 grams.
[...] “The chimps are eating 5 to 10% of their body weight a day in ripe fruit, so even low concentrations yield a high daily total — a substantial dosage of alcohol,” said Robert Dudley, UC Berkeley professor of integrative biology. “If the chimps are randomly sampling ripe fruit as did Aleksey, then that’s going to be their average consumption rate, independent of any preference for ethanol. But if they are preferring riper and/or more sugar-rich fruits, then this is a conservative lower limit for the likely rate of ethanol ingestion.”
[...] Dudley first began to suspect more than 20 years ago that the human appetite for alcohol was inherited from our primate ancestors, and wrote a 2014 book about his theory: The Drunken Monkey: Why We Drink and Abuse Alcohol. This “drunken monkey” hypothesis drew skepticism from many scientists — particularly those who study primates — who told him that chimps and other primates don’t eat fermented fruit or nectar. These nutrients typically contain alcohol produced by yeast metabolizing sugar, just as yeast ferments sugary grape juice into wine.
But over the years, Dudley’s theory has gained an increasing number of adherents. More primatologists now report seeing monkeys and apes eating fermented fruit, a practice that was recorded earlier this year among chimps in Guinea-Bissau. Researchers also have published papers about captive primates’ preferences for alcohol. Dartmouth University researchers in 2016 reported that when captive aye-ayes and slow lorises were offered nectar with varying percentages of alcohol, they finished off nectar with the highest alcohol content first — and then repeatedly revisited the empty high-alcohol containers as if they wanted more. In 2022, Dudley collaborated with researchers in Panama to document that spider monkeys consume alcohol-laden fermented fruit in the wild and express alcohol metabolites in their urine... (MORE - missing details, no ads)
https://youtu.be/rRgrxku64H4