Fermented fruits and nectars are nature's cocktails, and it turns out that many of our closest relatives like to indulge. Researchers have found that several primate species actually seek out nectars with higher concentrations of alcohol when given a choice, reports New Scientist.

The finding suggests that there might be an evolutionary advantage to imbibing, at least at low levels of consumption. It might also hint that alcoholism has its roots in evolution.

“This is the first study – albeit using captive primates – to show that there is a preference for higher levels of alcohol,” said Robert Dudley at the University of California in Berkeley, who wasn’t involved in the study.

For the study, researchers offered cups of sugary water, some of which were spiked with alcohol concentrations up to 5 percent, to two aye-ayes (a type of lemur) and one slow loris (a primate found in Southeast Asia). Sure enough, the boozier the liquid, the more the primates drank.

The amount of alcohol contained in the cups was not enough to get the primates drunk, but they still seemed to prefer the taste anyway. In fact, the aye-ayes were witnessed using their fingers to compulsively probe the cups long after the contents were consumed, suggesting they wanted to be certain to slurp up every last drop.

Though the primates' level of eagerness was unanticipated, the findings were not necessarily surprising. A primary source of food for many primates is fruit or nectar, and these sweet substances ferment fairly easily. Overly ripe fruits becomes alcoholic, and animals that eat them can occasionally get a little bit tipsy. For instance, the slow loris spends much of its time swigging bertam palm nectar, which has documented alcohol concentrations in the wild of up to 3.8 percent.

Another hint about our evolutionary inclination for alcohol comes from the presence of an enzyme called alcohol dehydrogenase in our systems. The enzyme helps us to detoxify alcohol, and it can also be found in chimpanzees and gorillas, as well as in aye-ayes.

So does that mean our primate relatives are lushes, or might there actually be an advantage to drinking alcohol? Well, as the study's researchers point out, alcohol forms vapors easily, and the smell of these vapors might help animals locate edible fruits and flowers. There may also be a dietary benefit to consuming alcohol in lower concentrations. Alcohol is known to slow down metabolism and promote fat storage.

That could be a good thing for hungry primates in the wild, but not such a good thing for humans with beer bellies. The invention of readily accessible hard liquor may have turned a healthy proclivity for alcohol into a very unhealthy habit. It might even help explain the abundance of alcoholism.

Boozy primates may hint at the roots of alcoholism
A proclivity for fruits and nectars with the highest alcohol content could offer some primates an evolutionary advantage.