As it turns out, the phrase "drunker than a monkey's uncle" may have a little truth to it. The Atlantic reports on potential human alcohol consumption and the dietary habits of monkeys—all in an effort to find out why we love alcohol so much.
The “drunken monkey” hypothesis suggests that animals that regularly consume fruit and nectar develop a natural affinity to alcohol, since fermentation, which occurs naturally in fruits and other materials where yeasts and sugars can interact and metabolize, leads to the production of ethanol. The fermenting material creates alcohol as a way of fighting off bacteria; this alcohol wafts into the environment, which as a result, can be sensed and followed by animals with a nose for it.
Essentially, so the hypothesis goes, animals are drawn to the scent of alcohol because they know it will lead them to food. Much like the human practice of the afternoon aperitif, where alcohol is enjoyed as an appetite stimulant (but also because a drink in the afternoon is a damn pleasure), the natural alcohol that occurs in fruit acts as a "feeding stimulant," the article suggests. Enjoying food with alcohol is as much about the pleasurable experience as it is about increasing energy levels. While it may be easier for us to search out a good bar with snacks, for the monkey who resides in the tropical forest where ripe fruit is found between long distances, the scent of alcohol acts as a beacon, guiding them to the next patch of boozy fruits.
Does this mean that the monkey can get drunk on all this funky fruit? As the Atlantic points out, there's a recurring cultural caricature of animals getting drunk in the wild, like a moose eating fermented apples in Sweden and getting stuck in the tree. But this phenomenon has not been fully scientifically studied, and it's not clear whether or not they actually do get drunk. The animals' actions could possibly be explained by the fact that the concentration of alcohol in the pulp of the fruit only gets as high as 3 percent—so even if a monkey is gorging on fruit all day, their level of alcohol consumption would not reach a high enough level for it to have any intoxicating effect. Many species also have enzymes that would degrade any traces of alcohol anyways.
Humans are different though. As the theory goes, when our ancestors started to walk upright some 10 million years ago, a change in these physiological abilities might have lead to an increased ability to metabolize alcohol. Our ancestors could have traversed more terrain and have had greater access to fruit that had been fermented for a longer period of time—so, more boozy. Thus, our love of alcohol began.
So in likelihood, we are drunker than a monkey's uncle, since a monkey can't really get drunk. Perhaps this evolutionary perspective on how genetics contribute to our drinking behaviors can help us understand our complicated relationship with imbibing. For better or for worse, we have accepted alcohol as a part of our social experiences, enjoying it as we share food together, and using it as a way to connect to other bipedal primates.