News release

From: The Royal Society

Urinary concentrations of a direct ethanol metabolite indicate substantial ingestion of fermenting fruit by chimpanzees

Ripe fruits worldwide routinely contain low amounts of alcohol, also known as ethanol, likely due to fermentation by budding yeasts. By measuring the ethanol content of the fruit they eat, we recently estimated that chimpanzees ingest an average of 14 grams per day of ethanol in their diet, the equivalent of 1-2 standard drinks in human terms. Here we returned to analyze the urine of chimpanzees for a chemical byproduct of ethanol metabolism in the liver, finding direct evidence of widespread ethanol ingestion. The method we demonstrate is cheap, portable and of use to anyone wishing to study foraging ecology.

Urine sample - Scientists have taken urine samples from chimpanzees to test how much ethanol they consume from eating ripe fruit. Using a test used to monitor abstinence in recovery programmes, half of the 20 chimpanzees at Kibale National Park, Uganda, exceeded levels that would rule out unintentional alcohol consumption in humans. The findings support the “drunken monkey” hypothesis – that the lack of ethanol aversion in apes could “be the origin of modern-day human attraction to alcohol”.