Bonobos lose their appetite if they experience disgust just like humans, according to a study which found that their curiosity transforms into caution when food is presented with faeces, soil or bad smells.
In nature, parasites and pathogens are everywhere, and can enter the body along with food. Humans have therefore adapted sensitivity to the signs of such pathogens, said researchers from Kyoto University in Japan.
In a series of experiments, bonobos were presented with different food choices involving novel food items: foods contaminated with faeces or soil; chains of food items linked to a contaminant; previously contaminated food; or only the odours of faeces or rotting food.
The study published in the journal Philosophical Transactions of the Royal Society B, found that although bonobos happily gobbled up clean food, they steadfastly avoided anything contaminated.
Moreover, their sensitivity to contamination risk seemed to wane the farther away a food item was located from the source of contamination.
Another experiment showed that bonobos are less likely to engage in exploratory activities like touching and tasting substrates, or even using tools to achieve a goal when confronted with 'bad' smells.
"These results fit with what one would expect if bonobos had a system of disgust driving their behavioral decision making," said Sarabian.
"Interestingly though, bonobo infants and juveniles showed much less precaution, matching human infant behaviour in similar contexts," she said.
One hypothesis is that while infants may get sick from this kind of behaviour, it helps them build their immune systems at a critical time in their development.
The team has yet to conclude if bonobos themselves express disgust in a way we can recognise, but plan to continue their research and further investigate the origins of disgust in humans.
"There's some evidence from humans and other animals -classically with rats - on what we call food neophobia, which is an inclination to stay away from or be cautious around new foods," said Andrew MacIntosh, senior author of the study.
"This might also be related to our tendencies to avoid things that might make us sick, with different individuals being more or less conservative in both cases," MacIntosh said.
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