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Apes who drink: Study finds chimps use leaves to chug, chug, chug

Some West African chimps enjoy taking a sip of grandma's cough medicine by sucking alcoholic sap from leaves and even drinking enough to get visibly intoxicated.

Researchers observed a chimp in Guinea using a leaf to do a shot of raffia palm sap. Miho Nakamura/Kyoto University via Royal Society Open Science

Humans aren't the only ones on this planet who enjoy a drink or seven at the end of a hard day of work or picking mites out of a neighbor's back fur. It turns out we might have some drinking buddies on the evolutionary scale.

Scientists from several universities, including Kyoto University in Japan, Oxford Brookes University in England and George Washington University in Washington, DC, published on Tuesday the results of a study that explains how chimpanzees use leaves as sponges and cups to enjoy an alcoholic beverage, sometimes drinking enough to get drunk. (I didn't say "legally drunk" because I assume AND HOPE it's already illegal for chimpanzees to operate a vehicle whether hammered or not.)

The researchers studied chimps over a 17-year period in the West African jungles of Bossou, Guinea, where the local villagers use the raffia palm to make an alcoholic beverage by collecting the sap and letting it ferment. The scientists noticed that when the locals weren't around, the chimps would enjoy a drink of the fermented sap by using leaves to cup or sponge up the liquid and drink it, "often in large quantities," according to the abstract for the study, which appears in the Royal Society Open Science Journal.

One of the researchers even captured a video of a chimp using the leaf to do a shot:

"Chimpanzees always used a leaf tool to drink, making a crushed or folded leaf 'sponge' from the leaves placed as a protective covering by villagers or from plants growing nearby," the study says. "This absorbent extractive tool was dipped into the small opening of the fermented palm sap container, then retrieved and put into the mouth for drinking. Individuals either co-drank, with drinkers alternating dips of their leaf-sponges into the fermented palm sap, or one individual monopolized the container, while others waited their turn."

This behavior gives some extra weight to something called the "Drunken Monkey Hypothesis," which may be the most hilarious-sounding hypothesis in the history of science (unless there's a "Punk Duck Hypothesis" or a "Rude Goldfish Hypothesis" out there somewhere).

Robert Dudley, a professor of integrative biology at UC Berkeley, proposed with his "Drunken Monkey Hypothesis" that humans' innate dependence for alcohol came from our Homo sapien ancestors who enjoyed the numbing effects of fermented fruits. This dependency developed over time through evolution and could explain our genetic need to have a few cocktails or even develop alcoholic dependencies to dangerous extremes. Dudley explained his theories and research in the book "The Drunken Monkey: Why We Drink and Abuse Alcohol."

Think about it. That means our drinking was literally caused by a monkey on our backs (or on the backs of our evolutionary scale, if you want to get technical).

The latest study appears to be just another example of humans' evolutionary link to chimpanzees. Last week, we learned that chimps not only prefer cooked food but are also capable of cooking their own grub. Researchers from Harvard and Yale published a study in which they observed chimps from the Jane Goodall Institute's Tchimpounga Chimpanzee Rehabilitation Center in the Republic of Congo using elementary cooking tools to toast sweet potatoes. They also learned how to use the device and understood its purpose, and would even save and transport food just so they could heat it up later.

At this point, I wouldn't be surprised if chimps also knew what foods go well with a crisp pinot noir.