The “Drunken Monkey” Hypothesis Might Explain Why Humans Enjoy Alcohol
Alcohol production and consumption seem to be among the most universal of human behaviors. Its face value avails no apparent association between our ingestion of ale and the organic ecology of apes, monkeys and other primates living in tropical forests. This beckons the question of why humans have an inherent drive for the drink. Could a psychoactive, socially acceptable substance occur in natural environments, and could our ancestors really have been exposed to alcohol on a regular basis?
When delving into the “drunken monkey” hypothesis, the statements suggest alcohol (specifically the ethanol molecule) is regularly consumed by all animals that eat fruits and nectar. Originally inducted by Louis Pasteur in the 19th century, fermentation is the natural-process derivative of yeast’s metabolic action on sugar molecules. Said molecules produce alcohol to battle and ultimately eradicate their bacterial competitors. The intoxicant accumulates at low concentrations within fruits and nectar. Additionally, it aerates into the environment, producing a downwind vapor trail that strongly suggests the presence of fruits and sugars.
If an animal can sense and follow this odor upwind, it will center in on the ethanol source and naturally the sugars inside the fruit. In tropical forests, ripe fruit springs up in spots, so it’s beneficial to have an ability for finding it over lengthy landscapes.
In addition to alcohol availing a useful long-distance sensory cue, it can act as a sustenance stimulant via the strongly studied “apéritif effect.” Further, many often imbibe when eating, and as a result, food ingestion is elevated. The psychoactive and serene aspects of alcohol indeed avails a happier disposition—particularly in social constructs—but they also ignite a sense of energy gain. For animals looking to unearth sparse nutritional resources in a rainforest, it’s similarly a smart move to expediently eat ripe fruits before their foes arrive. But do they actually become intoxicated?
There are many amusing anecdotes about supposed sauced animals in nature—e.g., the Swedish moose feeding on fermented apple and the American Midwest cedar waxwings being too buzzed to fly. But only on rare occasion have these “alcoholic” animals been scientifically studied—the hard evidence of inebriation is rare.
There are many amusing anecdotes about supposed sauced animals in nature—e.g., the Swedish moose feeding on fermented apple and the American Midwest cedar waxwings being too buzzed to fly. But only on rare occasion have these “alcoholic” animals been scientifically studied—the hard evidence of inebriation is rare. Instead, the innards of frugivores typically reach satiation long before incapacitating blood-alcohol levels are attained. While some animals can eat up to 10 percent of their body weight a day in ripe fruit, the typical concentrations of alcohol in fruit pulp are only about 0.5-3 percent—i.e., they never get drunk. Given that flying fruit-eating animals prey on the weak and vulnerable, that’s a fortunate, physical foundation for them. The majority of wild animals are equipped with effective enzymes to degrade any ingested alcohol.
However, humans differ in this respect. About 10 million years ago, as their primate predecessors progressively ascended to an upright position and eventually walked about bipedally, they underwent a change in terms of their physiological ability to process alcohol. DNA-sequence data and modern-day reconstruction of ancestral enzymes availed about a 20-fold increase in early apes’ ability to metabolize alcohol due to a single-point mutation in their genes—consistent with greater, dietary exposure to this molecule.
These animals wandered the forest floor and toiled around tundra while possibly obtaining better access to fallen fruit that had been fermenting longer—i.e., it contained more alcohol. While the initial advantages of this mutation remain a mystery, we’ve retained and matriculated it into modern times.
Contemporary society has a conflicted co-existence with the alcohol molecule. However, there are health highs for many who dabble in low-level drinking, but it’s mostly just a minimizing of cardiovascular risk. But those who lavish in high-level liquor consumption, there are substantial dangers to themselves and others—especially when riding in a wheeled vehicle. Can an evolutionary perspective on the booze-human relationship help us learn the apparently insoluble problem of alcohol addiction? At the smallest solution, recognition of an ancient and persistent, dietary exposure to the molecule suggests that alcohol-related behavior is partially pushed by deeply rooted reward pathways in the brain. And these responses are shared among creatures such as fruit bats, flies and our nearest, living relatives—the chimpanzees.
On the next occasion you imbibe, take in the rich history entailing protohumans foraging through forests, looking for fermented fruit.