(Roughly) Daily

It turns out, Andrew Coletti reports, that alcohol is consumed widely in nature– and may have played a role in human evolution…

… There’s something charmingly funny about the image of an animal drinking alcohol; it seems so incongruously humanlike. Some documentaries that show wild animals getting drunk off boozy rotten fruit, like this one from Botswana, use music and narration to emphasize the unexpected comedy of the scene. Scientists once believed that such behavior was random and accidental, especially in species not closely related to humans and other great apes. But more recent studies paint a very different picture. A research review published in October 2024 in Trends in Ecology & Evolution found that wherever ethanol—the active ingredient in alcoholic beverages—occurs in nature, it is routinely consumed by a variety of species, from insects and birds to rodents and monkeys.

In nature, “ethanol ingestion is far more common than was previously thought,” says Anna Bowland, a Ph.D. student in bioscience at the University of Exeter, England, who worked on the review. The paper cites research mainly from tropical regions like Central America and Southeast Asia, where yeast and bacteria ferment the natural sugars in fruit and nectar into ethanol in the hot sun. But a similar effect has also been observed in completely different environments. In Finland, when wild berries thaw in the warm sun after being bruised by frost, “they ferment quite quickly,” says Bowland. “And then as the birds come and feed on them, they’re ingesting alcohol.”

Because animals that feed on fruit and nectar ingest more ethanol on average, many of them show evolutionary adaptations to tolerate it. The review cites a study from the rainforests of Malaysia, which found that arboreal mammals like treeshrews, lorises, and squirrels regularly feed on fermented palm nectar with an alcohol concentration as high as 3.8 percent, comparable to a light beer. But intriguingly, says Bowland, “they don’t—in our anthropogenic sense—seem to get drunk,” meaning that they don’t display behaviors associated with inebriation in humans, like drowsiness or reduced motor skills. This suggests that treeshrews are particularly good at metabolizing ethanol.

Bowland explains that from an evolutionary standpoint, “it’s not beneficial for [animals] to get drunk, because that can lead to predation and injury and reduce survival, so they might not pass on their genes.” Animals that feed on a boozy food source have a better chance of survival if they can hold their liquor, so the presence of ethanol creates evolutionary pressure for tolerance….

… Another prominent example is the great apes. “Humans, chimpanzees, and gorillas—we all possess a mutation in one of our genes that greatly increases the rate at which we can metabolize and break down ethanol,” says Bowland, thanks to a digestive enzyme called ADH4. While other primates like Central American spider monkeys consume ethanol in fruit, and may, like fruit flies, be drawn to the smell, apes are particularly efficient at processing it. This has led some researchers to propose that the human fondness for ethanol goes back long before deliberate brewing and fermenting, to a dietary shift in our common ancestor with other apes.

Robert Dudley, a professor of Integrative Biology at the University of California, Berkeley, explored the evolutionary origins of human alcohol consumption in his book The Drunken Monkey Hypothesis. “Primates are ancestrally fruit-eaters, going back 45 million years,” says Dudley, based on evidence like the shape of their teeth. In modern apes, fruit still makes up 60 to 80 percent of the diet for chimpanzees and 90 percent for gibbons. According to Dudley, who was not affiliated with the 2024 study, genetic analysis of ADH4 in early apes shows that the enzyme became 20 times better at degrading ethanol about 12 million years ago. “This is right when the great apes are coming out of the trees and going bipedal, walking around, and, we think, now going after more ripe fruit crops that have already fallen down,” he says. Other foods becoming scarce, as well as the increased availability of fermenting fruit on the ground, may have increased pressure for prehistoric primates to adapt to an ethanol-rich source of nutrients.

“We’ve evolved with this molecule,” Dudley says of ethanol. His research suggests that the scent of ethanol “acts as a long-distance sensory cue” for primates, alerting them to the presence of edible fruit hidden among dense foliage. “Where there’s ethanol, there has to be sugar,” Dudley explains, and the scent of ethanol might even allow monkeys and apes to “assess individual fruits without wasting time biting into them.” Dudley also suggests that ethanol-rich fruit may stimulate the appetite of wild primates, encouraging them to take as much advantage of the available nutrition as possible. He compares this with the “aperitif effect” observed in humans, where consuming alcohol before a meal leads to increased food consumption, perhaps due to the stimulation of brain areas that regulate feeding behavior…

… Bowland is hopeful that her review will encourage further research into the interactions between animals and ethanol. Dudley agrees. “I think that the nice thing about that paper [is it] just points out the ubiquity of ethanol,” he says of the 2024 review. Ethanol is just a part of nature, found wherever there is sugar and microbes to ferment it. And while there’s still much to be explored, one thing is clear: If there’s anything that truly separates human beings from animals, it’s not alcohol…

No “dry January” in much of the animal kindom: “The Booze-Soaked Lives of Wild Animals,” from @aoofficial.bsky.social.

Apposite (or many better said, subsequent): “Peeing is contagious in chimpanzees, study suggests.”

* Frank Sinatra

###

As we investigate intoxicants, we might recall that it was on this date in 1935 that the beer can (created by the American Can Co.) was introduced by the Gottfried Krueger Brewing Company of Newark, New Jersey. Made of tin, it weighed 4 ounces– still lighter than glass bottles– and required a “churchkey” opener. Pabst, based in Milwaukee, followed quickly, introducing their own (“Blue Ribbon”) line of canned beer later in the year.

source