The laziest members of society not only annoy those who work hard, they may also be damaging their health.
An unequal sharing of the workload in communities could leave the most industrious individuals prone to accelerated ageing and more vulnerable to diseases, a study found.
Scientists at the University of Exeter studied the white-browed sparrow weaver, an African bird species that shares the burden of rearing offspring in an unequal way. The dominant males and females work hardest, providing most of the care for nestlings as well as defending the group’s territory.
The researchers found that after the breeding season in the Kalahari desert, the hardest-working dominant females suffered from weakened antioxidant defences, which help animals protect themselves against the damaging effects of free radicals.
The study, published today in the journal Functional Ecology, concludes: “Divisions of labour in animal societies can leave the hardest-working classes differentially exposed to oxidative stress, raising the possibility of hitherto unexplored impacts on health and ageing in social species.”
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The authors believe that the findings may have implications for the understanding of human health.
Dr Dominic Cram said: “When groups of animals live together, including humans, they often divide workloads and some individuals work harder than others. We wanted to investigate whether the hardest-working members are the healthiest and whether this allows them to work harder than everyone else. We also wanted to know whether work rates impact health, leaving the hardest workers in poor condition.
“Weaver societies are actually quite similar to human societies in many ways, with weaver social groups including related and unrelated birds, much like the family, friends and co-workers in our own social circles.
“Like weaver societies, uneven workload sharing is also common throughout human societies, from family groups (where one parent may work harder looking after the children) to society as a whole (where some people do a lot of hard physical work every day, while others work in an office).
“We also know that oxidative stress can have profound effects on human health, being involved in hundreds of disorders, including Parkinson’s, Alzheimer’s and ALS (motor neurone disease), diabetes, cardiovascular disease and cancer. Whether the hard work we do each day contributes to oxidative stress, in turn contributing to diseases and ageing, still needs to be clarified. Our data, linking oxidative stress to the weavers’ hard work under the Kalahari sun, suggests it might.”
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The study also suggests that there are “hidden physiological costs” to being a dominant member of a society.
It says that contrary to speculation that dominant individuals are able to work harder because they have greater antioxidant protection, they might achieve their status and carry out their tasks “in spite of” having poorer health defences.