What if the fondness of some humans for alcohol came from the taste of their distant ancestors for fermented fruits?
- Central American monkeys eat fermented fruit that contains ethanol
- Research has just shown that they consume this alcohol to store energy
- The question of whether human alcoholism finds its source in this eating habit of primates remains open…
If we sometimes appreciate alcohol consumed without any moderation, it may be because our very distant ancestors were looking for the ripest fruits to meet their caloric needs! For several years, a biologist from the University of Berkeley, Robert Dudley, had a hunch: in a book published in 2014, he suggested that our fondness for alcohol came directly from the attraction of monkeys for the smell. ethanol diffused by the ripe and fermented fruits they coveted. And a new study conducted by a primatologist from the University of California, Christina Campbell, lends credence to this thesis. She was published in the Royal Society Open Science journal.
The “drunk monkey” hypothesis
Interested in this so-called “drunken monkey” hypothesis, Christina Campbell and her team collected fruits eaten in the island of Barro Colorado in Panama by spider monkeys. They discovered two things: on the one hand that the concentration of alcohol in these remains of fruit was between 1% and 2% in volume under the effect of natural fermentation and that the urine collected from the monkeys living in freedom contained secondary alcohol metabolites. This means that the primates do not just eat these fruits for their taste but that they use the alcohol they contain to store energy.
“For the first time, we were able to show beyond a shadow of a doubt that wild primates, without human interference, consume ethanol contained in fruits!“, exclaims Victoria Campbell, admitting in fact that there is a grain of truth in the hypothesis of the “drunken monkey” and that “the propensity of humans to consume alcohol stems from a deep affinity of fruit-eating primates for the ethanol present in this food“.
Do monkeys feel the intoxicating effects of alcohol?
This is what Robert Dudley’s book already suggested, which showed that primates could eat fruits with an alcohol content of up to 7%. But in 2014, nothing made it possible to say, as is possible today, if the monkeys consumed these fruits only for their taste or if they digested the alcohol for their energy needs.
A crucial question remains: do the spider monkeys of Barro Colorado Island also seek the behavioral effects of this alcohol consumption, do they feel its intoxicating effects? Robert Dudley said he doubted it. And according to research conducted by Christina Campbell, monkeys ingest concentrations of alcohol that are only half those of “human” so-called “low-alcohol” drinks… So the “drunken sign” would remain of first a picture!
And yet, the same fruits that they consume today were also used for millennia by the human populations of the region to make “chicha”, an alcoholic drink! So, alcoholism, a “Darwinian” phenomenon? The Californian primatologist settles this debate with a “Norman answer”: “Our human ancestors may have preferred fruits loaded with ethanol because they contain more calories… but the psychoactive and hedonic effects of this alcohol may also have led to an increase in their consumption…“
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