Wild Chimpanzees: A Surprising Taste for Alcohol
If we were to test wild chimpanzees for blood alcohol levels, many would likely yield positive results. This isn’t due to a hidden bottle of whiskey but rather the natural sugars present in the fruits they consume. The microbial fermentation of these fruits can produce alcohol, which has spurred scientific debate about whether our attraction to alcohol stems from an ‘evolutionary accident’ or a genetic legacy from our primate ancestors. Recent studies shed light on this fascinating connection.
A New Study on Chimpanzee Alcohol Consumption
Published by researchers at the University of California, a significant study indicates that wild chimpanzees consume substantial amounts of ethanol as part of their daily diet. The research team focused on chimpanzees in Kibale National Park, Uganda, opting for non-invasive methods by analyzing the urine of 19 wild chimpanzees instead of conducting blood tests. They sought not raw ethanol, but a specific biomarker known as ethylglucuronide, indicating that ethanol has been metabolized in the body.
The Chimpanzee Diet
The key to this discovery lies not in man-made alcohol but in the natural fruits consumed by the chimpanzees. The research revealed that during the study, the chimpanzees primarily fed on a canopy tree species known as the African star apple.
This fruit was found to contain alcohol at a concentration of about 0.09%, and in certain harvests, this figure could increase to 0.4%. Such natural fermentation results in a surprising intake of alcohol.
Research Findings
After conducting urine analyses on the chimpanzees, the results were telling. Out of the 20 individual samples collected, 17 tested positive for ethylglucuronide, with concentrations exceeding 300 ng per milliliter of urine. Furthermore, in a subset of 11 positive samples, 10 also surpassed a clinical threshold of 500 ng/ml.
The “Drunken Monkey” Hypothesis
The results suggest a daily intake of approximately 14 grams of ethanol for these chimpanzees, equivalent to about one and a half standard drinks per day in human terms. This evidence supports the well-known “drunken monkey” hypothesis. According to this hypothesis, human attraction to alcohol likely has evolutionary roots, originating from ancestral adaptations to locate ripe fruits, which could be detected by their ethanol scent.
Challenges of Modern Alcohol Consumption
However, this ancient inclination towards low-level ethanol consumption presents an evolutionary mismatch with today’s society. While our primate ancestors thrived on a fruit-rich diet providing moderate amounts of ethanol, contemporary humans are exposed to distilled alcohol in excessive quantities, far removed from the natural consumption patterns of their forebears.
Implications for Future Research
This groundbreaking discovery not only transforms our understanding of primate dietary habits but also paves the way for further research examining how this natural alcohol consumption might influence chimpanzee social behaviors, including aggression and mating patterns.
Images | David Trinks Brian Jones