Chimpanzees consume the equivalent of at least one alcoholic drink per day as they eat ripe, fermenting fruit, a study published on Wednesday said.
The study was carried out in the wilds of Africa, where the animals live.
The researchers collected fruits that chimps eat and measured their ethanol content, which is produced as sugar ferments.
Photo: AFP
They concluded that the animals consume alcohol on a daily basis — and not just a little.
Through the large amount of fruit that chimps eat, the researchers said that they take in about 14g of alcohol per day.
Correcting for body size, it is like the chimps are drinking a pint of beer per day, said Aleksey Maro, lead author of the study published in the journal Science Advances.
“It’s not an insubstantial amount of alcohol, but very diluted and more associated with food,” said Maro, who is a doctoral candidate at the University of California, Berkeley.
“We’ve seen for the first time that, indeed, our closest living relatives are consuming physiologically relevant doses of alcohol routinely daily,” Maro said.
This is in line with the “drunken monkey theory” espoused more than a decade ago by US biologist Robert Dudley, who coauthored the new study.
The theory is that humans liking alcohol and being able to metabolize it stems from primate ancestors ingesting it daily through the fruit they eat.
“The drunken monkey hypothesis is becoming more and more a reality,” Maro said. “Its name is unfortunate. A better name would be the evolutionary hangover.”
Nathaniel Dominy, a professor of anthropology and evolutionary biology at Dartmouth College who did not take part in this study, welcomed it.
“The paper is a tour de force,” Dominy told reporters.
He said it “puts to rest the debate over the prevalence of ethanol in tropical fruits.”
However, the study raises new questions on the biological and behavioral consequences of chronic low-level ethanol exposure for primates, he said.
Another unanswered question is whether chimps search out boozy fruit or just eat it when they find it.
The researchers in this study said they did not know.
The issue of chimps ingesting alcohol will remain under study to learn more about the origins of human alcohol consumption, and assess its risks and possible benefits, Maro said.
“We can learn about ourselves through the chimpanzees,” he said.
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