New research lends support to the idea that humans’ weakness for alcohol stems from our ancestors’ taste for naturally fermented food.
“Our predilection for psychoactive substances is difficult to explain,” said Samuel Gochman of Dartmouth College. “At best it carries opportunity costs – coming at the expense of foraging, mate acquisition and retention or childcare – and at worst it could make one more vulnerable to predation. So, on first principles, evolutionary theory predicts that we should avoid psychoactive substances.”
Yet many primates, including ourselves, produce an alcohol-digesting enzyme, which would not be necessary were alcohol not a component of the diet.
One possible reason why is that ingesting alcohol is unavoidable in diets rich in fruit, which is liable to ferment through the action of wild yeasts. Other primate species rely heavily on supping nectar, which is similarly prone to fermentation. But it could be that imbibing alcohol has direct benefits.
“Alcohol has a high calorie content, and access to this exclusive resource would create an evolutionary advantage over organisms that cannot utilise this food,” said Gochman.
To investigate, the ecologist and his colleagues tested the alcoholic inclinations of two species of primate, the aye-aye and the slow loris, both of which possess the alcohol-digesting enzyme and are partial to nectar.
In both cases, the animals preferred higher-proof versions of their favourite tipple.
Aye-ayes and slow lorises split from monkeys and apes early in primate evolution, suggesting that our own penchant for the hard stuff has ancient roots that led ultimately to our creation of alcoholic beverages.
Indeed, Gochman argues that domesticating wild alcohol-producing yeasts was a significant historical development: “The rise of complex societies revolves around species domestication, but few people would elevate yeast to the level of cereals or dairy-producing animals. We think that is a mistake — yeast was far more important.”