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Wild Chimps May be Alcoholics

Jun 10, 2015 10:24 AM EDT

Wild chimpanzees may be alcoholics, according to new research, which found the animals going out of their way to get drunk on palm wine in West Africa. This, scientists say, can help to shed light on the evolution of humans' closest relatives.

Of course, it is known that nearly all modern human cultures partake in drunken booze sessions every once in a while (or more) given that we have access to fermentable materials. Now, new findings are serving up the best evidence yet that chimps also have a taste for alcohol - and will even go out of their way to drink it.

This idea led scientists to propose what is known as the "Drunken Monkey Hypothesis" - that the common ancestor of modern apes and humans adapted a genetic mutation to help break down alcohol, and thus made it easier to digest overripe and fermenting fruit. Believers in the hypothesis suggest that the benefits of this liquid diet may explain why humans today enjoy drinking alcohol.

While the new study, published in the journal Royal Society Open Science, doesn't prove the Drunken Monkey Hypothesis, it does show that chimpanzees are not deterred by alcohol.

In fact, researchers say they have confirmed, for the first time, that wild apes habitually drink alcohol.

"The consumption of ethanol by modern-day humans is nearly universal, being found in every society with fermentable raw materials," lead author Kimberley Hockings, an anthropologist at Oxford Brookes University, told NBC News. "However, aside from enforced ingestion in captive experiments or anecdotal observations in wild apes, the habitual and voluntary consumption of ethanol has been documented until now only in humans."

For 20 years, Hockings and her colleagues have been watching wild chimpanzees living near the village of Bossou in the West African country of Guinea. There, local villagers tap into Raffia palm trees and hook up plastic containers to collect the flowing sap, which quickly ferments into tasty palm wine.

It turns out the chimps like this sweet wine as well. The researchers documented 51 instances between 1995 and 2012 in which chimps crumpled up palm leaves to use as a sort of sponge to soak up the wine.

"I was fascinated by this behavior," Hockings told Live Science. "To harvest the palm wine, chimpanzees at Bossou use a leafy tool as a spongy drinking vessel."

"This new use of elementary technology shows once again how clever and enterprising humankind's nearest living relations are," she added.

The research team also calculated the palm wine's alcohol content, finding it averaged about 3.1 to 6.9 percent. For comparison, beer averages between 3 and 6 percent alcohol, whereas wine can contain 7 to 14 percent alcohol.

And these booze-loving apes sure liked to drink. On average, they drank about a liter of fermented sap. During one of the drinking sessions, one alcoholic chimp even guzzled down three liters of wine.

"Some of the chimpanzees at Bossou consumed significant quantities of ethanol and displayed behavioral signs of inebriation," the researchers wrote.

A number of chimps would rest immediately after drinking the palm wine, for instance, and one male in particular seemed restless and agitated afterward.

Do these findings all add up to chimps being alcoholics?

Scientists can't say for sure, "However, our data clearly show that alcohol is not an absolute deterrent to chimpanzee feeding in this community," Hockings said.

Researchers plan to conduct future studies to find out once and for all if the Drunken Monkey Hypothesis holds water.

For more great nature science stories and general news, please visit our sister site, Headlines and Global News (HNGN).

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