In forests in Uganda and the Ivory Coast, chimpanzees swing in trees and devour figs and plum fruits. Some fruits they pick up from the ground.
During a day, an average chimpanzee eats about 4.5 kilograms of fruit of different ripeness, which contains on average 14 grams of ethanol. For a chimpanzee, it is an alcohol content equivalent to two drinks for a human.
Researchers at the University of Berkeley in California, USA, have found this out by measuring the alcohol content in the fruits that exist in the apes' home environment.
Our ancestors
The study's author, Professor Robert Dudley, has worked for several decades based on a hypothesis about the "intoxicated ape". He suspects that humans have inherited the craving for alcohol from the apes, given that the apes' diet is based on ripe and overripe fruit.
The satisfaction associated with drinking alcohol leads to increased eating, says Dudley to the American CBS News.
This does not mean that there are large drinking parties in the forests of the Ivory Coast and Uganda. The chimpanzees would need to eat even larger quantities of fruit, until their stomachs swell up, to become properly intoxicated, emphasizes Dudley and his colleagues.
"Strong force"
Their study does not provide an answer to whether chimpanzees choose fruit based on alcohol content, sweetness, or other nutritional values. But the researchers believe they have been strengthened in their opinion; that humans' ancestors developed a desire for alcohol by being exposed to tropical fruits with a certain amount of ethanol.
Even if our eating habits have varied, the tendency to want to consume quickly when this molecule is present can still be a strong force, says Robert Dudley.
The chimpanzee (Pan troglodytes) is, along with the bonobo (Pan paniscus), humans' closest relative. It shares nearly 99 percent of its DNA with modern humans.
The range extends from Senegal in the west across West Africa and Central Africa to Uganda and Tanzania in the east.
The chimpanzee is strongly threatened, the number is currently believed to be between 345,000 and 470,000.
