Topic for May. 8. (Thur)

[Alex !]

Wild chimpanzees filmed by scientists bonding over alcoholic fruit

-posted on the guardian.com 

Footage of apes consuming fermented breadfruit leads researchers to ask if it may shed light on origins of human feasting.

Humans have gathered to feast and enjoy a tipple together for thousands of years, but research suggests chimpanzees may also bond over a boozy treat.

Wild chimpanzees in west Africa have been observed sharing fruit containing alcohol – not in quantities to get roaring drunk but, possibly, enough for a fuzzy beer buzz feeling.

The researchers, led by scientists from the University of Exeter in the UK, caught chimpanzees on film sharing fermented African breadfruit in Guinea-Bissau’s Cantanhez national park.

“For humans, we know that drinking alcohol leads to a release of dopamine and endorphins, and resulting feelings of happiness and relaxation,” said Anna Bowland, from the Centre for Ecology and Conservation at Exeter’s Penryn campus in Cornwall.

“We also know that sharing alcohol, including through traditions such as feasting, helps to form and strengthen social bonds.

“Now we know that wild chimpanzees are eating and sharing ethanolic fruits, the question is: could they be getting similar benefits?”

Using motion-activated cameras, the researchers filmed chimpanzees sharing the large, dense and fibrous fermented fruit on 10 occasions. The fruit shared was tested for alcohol content. The highest level found was the equivalent of 0.61% alcohol by volume (ABV).

“Chimps don’t share food all the time, so this behaviour with fermented fruit might be important,” said Kimberley Hockings, also from the University of Exeter.

Though the alcohol level is relatively low, the chimpanzees ate a lot of fruit every day so might ingest a fair quantity of alcohol, she said. “They can feed on kilograms of the stuff every day. It’s probably analogous to us sipping on a light beer.”

Hockings and her colleagues published a paper in 2015 describing how chimpanzees in west Africa stole and consumed palm sap alcohol created by humans. Some of them appeared to become troublesome, causing mischief such as not letting others build their night nests.

The researchers behind the latest study, however, said chimpanzees were unlikely to get “drunk” on the breadfruit because it would not improve their survival chances.

The sharing seemed to take place between all ages and sexes. Two adult females, nicknamed Chip and Até, were seen ignoring a larger hunk of breadfruit in favour of a smaller but fermented piece.

Two adult males, Mandjambé and Gary, were observed approaching ripe breadfruit with aggressive stances. Mandjambé claimed a piece and began to feed, while another adult male, Bobby, kept Gary at bay. They all had a taste of the ripe breadfruit in the vicinity in the end.

The paper, which appears in the journal Current Biology with the title “Wild chimpanzees share fermented fruits”, asks the question: “Do the origins of feasting behaviour derive from a shared common ancestor?”

Hockings said: “We need to find out more about whether the chimpanzees deliberately seek out ethanolic fruits and how they metabolise it, but this behaviour could be the early evolutionary stages of feasting. If so, it suggests the human tradition of feasting may have its origins deep in our evolutionary history.”

She said the number of observations was small but they could lead to “an explosion” of research into the topic.

The use of fermented foods and drinks by humans is so widespread as to be considered ubiquitous, with their use largely linked to dietary benefits and social bonding.

The discovery of a molecular adaptation in an alcohol dehydrogenase enzyme that greatly increased ethanol metabolism in the common ancestor of African apes suggests that the incorporation of fermented fruit in the human diet has ancient origins.

However, little is known about the inclusion of ethanolic foods in the diet of nonhuman great apes. Here, we document for the first time the repeated ingestion and sharing of naturally fermented African breadfruit (Treculia africana) with confirmed ethanol (alcohol), by wild chimpanzees (Pan troglodytes verus) in Cantanhez National Park, Guinea-Bissau.

Widespread plant food sharing in great apes and the recent confirmation of ethanol presence in diverse fruit species suggest the sharing, and dietary incorporation, of ethanol-containing foods is extensive and may have played a long-standing role in hominoid societies.

Given the widespread presence of fermented fruits in nature5,9, the feeding and sharing of fermented foods is likely to extend across great ape populations, as multiple species of African great apes have been recorded sharing the fruits of T. africana.

Sharing itself is suggested to play a key role in social bonding in wild chimpanzees.Much like grooming, alcohol can reduce stress levels and trigger the endorphin system, which may further promote sociality and sharing.

Social eating and alcohol consumption comprise two key components of feasting behaviour in humans. But do the origins of feasting behaviour derive from a shared common ancestor? Our data provide the first evidence for ethanolic food sharing and feeding by wild nonhuman great apes, and supports the idea that the use of alcohol by humans is not ‘recent’ but rather rooted in our deep evolutionary history.

To fully understand this in a social context requires data on the role of social alcohol consumption in reinforcing social bonds and building social capital, including the exchange of other goods, between extended kin and non-kin, and the degree to which ethanol ingestion is intentional or not.

This necessitates long-term observations of individuals with well-established relationships where changes in feeding and social behaviour can be monitored, alongside measurements of ethanol in foods.