Alcohol consumption is injurious to health; however, chimpanzees get a daily dose of alcohol from fermented fruits that they consume. Estimates suggest that they ingest the equivalent of one alcoholic drink. A deep dive into this behavior can be pivotal in explaining human alcohol intake.
The scientific community has long been aware that chimpanzees consume alcohol. However, this study, published in the journal Science Advances, is the first to provide an approximation of the amount of alcohol they consume per day.
The scientists observed two groups of chimpanzees, one in Uganda and the other in Côte d’Ivoire (Ivory Coast). The team collected samples of the fruits they consumed and then estimated the amount of ethanol they ingested. Reports declare that these primates consume 14 grams of alcohol every day, equivalent to 1.4 alcoholic drinks.
“The chimps are eating 5 to 10% of their body weight a day in ripe fruit, so even low concentrations yield … a substantial dosage of alcohol,” said senior study author Robert Dudley, a professor of integrative biology at the University of California, Berkeley.
Dudley is renowned for bringing forward the “drunken monkey” hypothesis, which states that our preference for alcohol is reminiscent of the ancient tendency as primates sought out and ate ripe fruits that had alcohol in them, and were rich in sugar.
The researchers used three different methods on sampled ripe fruit pulp from 20 species in both Uganda and Côte d’Ivoire (Ivory Coast), to estimate the alcohol content.
Estimates indicate that the ripe fruits that entice chimpanzees contain an average of 0.31% to 0.32% ethanol, and chimpanzees consume around 4.5 kilograms (10 lbs) of fruit per day. This indicates that they ingest 14 grams (0.5 ounces) of alcohol daily.
The chimps ate a type of fig in Uganda and a fruit resembling plums in Côte d’Ivoire (Ivory Coast), which had the highest alcohol concentration. Scientists infer that these fruits have more sugar to ferment because they are riper.
According to conservation scientist Kimberley Hockings, an associate professor at the UK’s University of Exeter, chimpanzees don’t get drunk by ingesting alcohol in this manner, as they do so throughout the day. It remains to be studied whether chimpanzees are deterred or attracted to alcohol in general.
As for Dudley’s “drunken monkey” hypothesis, it was met with skepticism. However, newer evidence suggests that they eat fermented fruits, supporting Dudley’s claims. He also says that the consumption of alcohol isn’t unique to primates, as the smell of ethanol helps animals find food with greater sugar content. This is particularly notable in all fruit-eating animals and in a few nectar-feeding animals. Dudley also talks of alcohol abuse and attraction of modern humans, and suggests that federal funding for research into this matter can address the problem. According to him, modern humans, easily lured by alcohol, might have an evolutionary connection.
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