Tree shrew could reveal the secrets of alcohol addiction

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German scientists observing an alcohol swilling jungle mammal believe it could hold the key to why humans are so fond of drinking

Hamburg  -- A tiny beer-swilling, rodent-like jungle creature which drinks the equivalent of a case of 3.8 per cent beer every night and never gets inebriated may hold the clue to the ultimate hangover cure for humans, according to German scientists.

The Malaysian pen-tailed tree shrew drinks the beer-like fermented nectar of the flowers of the bertram's palm in such quantities that the equivalent amount of alcohol would cause a human to collapse in a drunken stupor, say the scientists from Bayreuth University in Germany.

Frank Wiens and Annette Zitzmann of the Department of Animal Physiology at the University of Bayreuth says the palm-flower nectar is so potent that the whole rain forest in the Segari Melintang Forest Reserve in Western Malaysia reeks of alcohol like a distillery.

Dr Wiens and his fellow researchers set up cameras to document the nocturnal creatures who visit the palm flower "bar". They found that each night, pen-tailed tree shrews drink copiously of the palm's high-powered nectar. In fact, the tree shrews go on a natural-palm-beer binge that lasts two and a half hours on average per night.

Amazingly, the German scientists said there was little evidence that the tree shrews consumed anything but this powerful nectar. And they showed no signs of inebriation or hangover despite their nightly binges.

The tiny creature has been living on a diet that is the equivalent of nothing but beer for up to 55 million years - long before humans discovered the art of brewing and distilling alcoholic beverages some 9,000 years ago.

"Nevertheless, this Malaysian tree shrew is never drunk. This suggests a beneficial effect, and sheds a whole new light on the evolution of human alcoholism," the scientists write in a paper published in the current issue of the scientific journal the Proceedings of the National Academy of Sciences (PNAS).

Citing what they call "the first recorded chronic alcohol intake in the wild", the Bayreuth scientists speculate that the tree shrew's body chemistry could hold beneficial clues for medicinal treatment in humans - such as a cure to the hangover. It is also possible that the development of breweries and distilleries was an outgrowth of a primordial drinking habit which began when our ancestors were still climbing trees.

"The pen-tailed tree shrew is considered a living model for extinct mammals representing the stock from which all extinct and living tree shrews and primates radiated," they add.

"Therefore, we hypothesize that moderate to high alcohol intake was present early on in the evolution of these closely related lineages."

The ramifications are profound, indicating that binge drinking is an instinct which once served an evolutionary purpose.

"Alcohol use and abuse can no longer be blamed on the inventors of brewing of about 9,000 years ago," say the scientists. "So far, the current theories on alcoholism have stated that mankind and its ancestors were either used to taking no alcohol at all or maybe only low doses via fruits - before the onset of beer brewing.

"As brewing is such a recent event on the evolutionary time scale, we were not able to develop an adequate defence against the adverse effects of alcohol and the partly hereditary addiction. Mankind is suffering from an evolutionary hangover," the scientists write.

"Alcohol consuming tree shrews are not real shrews. In fact, they belong to the primates' closest living relatives and are ecologically and behaviourally comparable to their extinct ancestors that lived more than 55 million years ago," say the scientists.

"Studying these fascinating creatures is an unexpected golden opportunity to learn about the causes and consequences of real-life drinking."

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