SYDNEY - In the wild, spider monkeys restrict their daily protein intake in a similar way to humans in order to avoid obesity, suggesting common evolutionary origins.
Annika Felton, a departmental visitor at the Fenner School of Environment and Society at Australian National University (ANU), spent a year in the Bolivian rainforest following 15 Peruvian spider monkeys, observing their individual dietary habits.
‘We found that the pattern of nutrient intake by wild spider monkeys, which are primarily fruit eaters, was almost identical to humans, who are omnivores,’ Felton said.
‘Spider monkeys appeared to aim for a target amount of protein each day, regardless of whether they only ate ripe fruit or mixed in other vegetable matter as well. This result was unexpected because, previously, ripe fruit specialists were thought to be ‘energy maximisers’.
‘In other words, they would aim to maximise their daily energy intake. Our findings show this is not the case.’ Felton said that the consequence of tight protein regulation is the same for monkeys and humans.
If the diet is poor in protein but rich in carbohydrates and fats (energy dense food) then individuals will end up ingesting a great deal of energy in order to obtain their protein target, which can lead to weight gain.
This ‘protein leverage effect’ is thought to play a significant role in the human obesity problem found in modern western societies.
‘Our results suggest that an adjustment of the nutritional balance of diets as a means to manage human obesity might similarly be an option for mitigating obesity in captive primates,’ Felton said.
‘Similarity in the regulatory pattern of protein intake between distantly related species, such as humans and spider monkeys, possessing very different dietary habits, may indicate that the evolutionary origins of such regulatory patterns are quite old.
If we are not dealing with convergent evolution here - in other words that spider monkeys and humans have evolved this trait independently - then this trait may have been shared by our common ancestor, said an ANU release.
The study was published in Behavioural Ecology.