New discovery strengthens 'drunk monkey' hypothesis

US scientists have discovered for the first time a primate that consumes and metabolizes ethanol without human intervention.

Over the past 25 years, biologist Robert Dudley from the University of California–Berkeley (UC Berkeley) has devoted much attention to the human behavior of alcoholism. In 2014, he wrote a book suggesting that our love of alcohol dates back millions of years, when primate ancestors were attracted to the scent of ethanol, also known as alcohol or alcohol. ethylic, from ripe and nutritious fruit. Dudley calls this idea the "drunk monkey" hypothesis.

In a new study published in the journal Royal Society Open Science last month, primatologist Christina Campbell and graduate student Victoria Weaver at California State University, Northridge (CSUN) say they have found for the first time. evidence supporting Dudley's hypothesis.

Black-armed spider monkey resting on a tree.

Campbell and Weaver took a field trip to Barro Colorado Island in Panama, where Dudley often visited, and began thinking about the role ethanol plays in animal diets. They collected portions of fruit that had been discarded by black-handed spider monkeys (Ateles geoffroyi) after eating and found that it contained alcohol levels - a byproduct of natural fermentation in ripe fruit - ranging from 1% to 1%. 2%, which is about half that of low strength beers.

Not stopping there, the team continued to collect urine from these wild monkeys and found that it contained a secondary metabolite of alcohol. This suggests that the black-armed spider monkey is indeed using ethanol for energy.

"For the first time, we can demonstrate that primates consume ethanol without human intervention," notes Campbell. "Black-handed spider monkeys are likely to eat fruit containing ethanol for calories, because fermented fruit provides more calories than unfermented fruit. Higher calories mean more energy."

Black-handed spider monkeys choose ripe fruit containing ethanol to absorb more calories.

Despite naming his theory "drunk monkeys", Dudley suspects that monkeys do not fall into a drunken state like humans, because their intestines will be filled with food before reaching the point of intoxication. However, ethanol may provide primates with physiological benefits, such as some anti-microbial benefit in the food they consume.

Campbell further notes that monkeys' high calorie needs may have influenced the decisions of human ancestors when choosing fruit to consume. Our ancestors may also have preferred fruit that contains more ethanol because it has more calories. However, this is just one study and more evidence is needed to confirm.