Species which use the most energy in their daily lives die out quicker than less energetic animals, say evolutionary biologists

It is the perfect comeback for those who are admonished for not pulling their weight. Never mind that work is piling up, being lazy is a winning evolutionary strategy that postpones the extinction of the species.

That, at least, is one interpretation. Researchers who studied nearly 300 forms of mollusc that lived and died in the Atlantic over the past five million years found that a high metabolism predicted which species had gone the way of the dodo.

The sea snails, sea slugs, mussels and scallops which burned the most energy in their daily lives were more likely to have died out than their less energetic cousins, especially when they lived in small ocean habitats, the scientists found.

While the causes of extinction are varied and complex, the work points to a new link between the rate at which animals use energy to grow and maintain their body tissues and the length of time the species has on Earth.

“The lower the metabolic rate, the more likely the species you belong to will survive,” said Bruce Lieberman, a professor of ecology and evolutionary biology who led the research at Kansas University. “Instead of ‘survival of the fittest’, maybe a better metaphor for the history of life is ‘survival of the laziest’, or at least ‘survival of the sluggish’.”

The scientists examined 299 species of gastropods, such as snails and slugs, and bivalves, including mussels and scallops, that lived in the Western Atlantic Ocean any time from the Pliocene more than five million years ago to the present day. When the researchers calculated resting metabolic rates for each species, they found that energy use differed markedly for the 178 species that had gone extinct compared with those that live on today. The work is published in Proceedings of the Royal Society B.

“The probable explanation is that things that were more sluggish or lazy had lower energy or food requirements and thus could make do with little when times were bad,” said Lieberman.

The work could help conservationists to better forecast which species are likely to die out first as global climate change hinders food production. The next step is to find out whether metabolism plays a role in the extinction rates of other animals, including those that live on land.

“This result doesn’t necessarily mean that lazy people are the fittest, because alas sometimes those lazy people are the ones that consume the most resources,” Lieberman added. “Humanity’s laziness, when it comes to trying to arrest the changes to the planet we are causing, may be the biggest peril our own species faces.

“But in a nutshell our work indicates that being sluggish can make you more likely to survive. So, here’s to a nap, after we solve our planet’s environmental crisis.”