Researchers have reported that wild chimpanzees consume the equivalent of a small bottle of lager per day through their diet of ripened fruit. The study suggests that the human preference for alcohol may originate from primate ancestors that relied on fermented fruit as a food source.
"Human attraction to alcohol probably arose from this dietary heritage of our common ancestor with chimpanzees," said Aleksey Maro of the University of California, Berkeley.
Chimpanzees, like other animals, often feed on fallen ripe fruit. This study is the first to quantify how much ethanol, or pure alcohol, they may be ingesting.
The research team analysed fruits such as figs and plums eaten by chimpanzees in Côte d'Ivoire and Uganda. Their findings show that chimpanzees consume around 14 grams of ethanol daily, equivalent to nearly two UK alcohol units, or roughly one 330 ml bottle of lager. Fruits with the highest alcohol levels were the most commonly consumed.
The findings support the "drunken monkey" hypothesis, first proposed by Robert Dudley of the University of California, Berkeley, who co-authored the study. The hypothesis suggests that humans inherited their appetite for alcohol from primate ancestors.
Scientists were initially sceptical of the idea, but more observations of chimpanzees feeding on fallen, fermenting fruit have been reported in recent years. "What we're realising from this work is that our relationship with alcohol goes deep back into evolutionary time, probably about 30 million years," said Catherine Hobaiter, a primatologist at the University of St Andrews, who was not part of the research team. "Maybe for chimpanzees, this is a great way to create social bonds, to hang out together on the forest floor, eating those fallen fruits."
Dr Kimberley Hockings of the University of Exeter, who was also not involved in the research, noted that the chimpanzees were not consuming enough alcohol to become drunk. "This would clearly not improve their survival chances," she said.
According to the International Union for the Conservation of Nature, chimpanzees are endangered, with major threats including deforestation from farming, logging, and infrastructure development.
Source: BBC