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| A river snail. (scubaluna/iStock) |
People will tell you laziness is bad. Get up and be active, they say. Move your body around, and it won't just keep you fit, it could even keep you young.
That's good advice, but new research suggests being inherently lazy isn't always as bad as is made out – and could actually be an evolutionary survival mechanism that defends slacker species from the oblivion of extinction.
"We wondered, 'Could you look at the probability of extinction of a species based on energy uptake by an organism?'" explains palaeontologist Luke Strotz from the University of Kansas.
The answer, it turns out, is yes. At least for molluscs.
Strotz and his team analysed almost 300 species of mollusc – including aquatic molluscs, but also snails and slugs – that have inhabited the Western Atlantic since the Pliocene epoch began some 5.33 million years ago.
Not all of them lasted the distance. And that's where things get interesting.
"We found a difference for mollusc species that have gone extinct over the past 5 million years and ones that are still around today," Strotz says.
"Those that have gone extinct tend to have higher metabolic rates than those that are still living. Those that have lower energy maintenance requirements seem more likely to survive than those organisms with higher metabolic rates."
In a sense, of course, this isn't altogether surprising. Energy keeps animals alive, and it stands to reason that animals that require more of it to function could be more vulnerable, especially over periods lasting millions of years.
Up until now, though, this hypothesis was largely just assumed, but now it's been observed.
In the researchers' mollusc microcosm, it was the 'lazy' snails, slugs, and scallops – or rather the species exhibiting a low basal metabolic rate (BMR) – that enjoyed better chances of pulling through.
"Maybe in the long term the best evolutionary strategy for animals is to be lassitudinous and sluggish – the lower the metabolic rate, the more likely the species you belong to will survive," explains one of the team, evolutionary biologist Bruce Lieberman.
"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 researchers are eager to emphasise that their laziness proxy of BMR isn't the only factor affecting mollusc survival, but it's thought to be one of the integral mechanisms that help to drive extinction, particularly in species that aren't spread over a diverse geographical area.
"For instance, the difference we observe between BMR of extinct and extant species may reflect variation in a constellation of organismic traits such as developmental rate, time to maturity, lifespan and population size, with a primary causal factor driving these differences being variation in the rate of energy uptake," the authors write in their paper.
Of course, what's good for mollusc species is not necessarily good for me and you. So should we aspire to sluggishness? Should we be the slug?
Unfortunately, the answer is no.
Just because mollusc species with naturally low BMRs have enjoyed better survival prospects since basically forever ago doesn't mean individual human beings can somehow 'opt in' to this metabolic magic. It doesn't work that way.
"You can't just decide to be lazy as an individual and expect to live longer," Strotz explained to Inverse.
That said, the researchers think their finding may be generalisable to other marine creatures, and they say there's a chance it could extend to other kinds of animals too, including vertebrates and critters who walk on land.
At the human scale, of course – a world away from the non-concerns of slacker snails – we have bigger fish to fry. Laziness isn't our saviour. In terms of survival, it's the exact opposite.
"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," Lieberman explained to The Guardian.
"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."
The findings are reported in Proceedings of the Royal Society B.
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