Often we hear "survival of the fittest" as a notion toward different life scenarios, be it health, sports, or business. The idea applies to most of the cases, but if we are to consider the real-world survival of some animal species, chances are the laziest ones are more likely to live longer.

This is what a group of researchers from the University of Kansas found after taking a close look at some extinct as well as living species of bivalves and gastropods in the Atlantic.

As part of the work, the team analyzed the physiology and evolution of as many as 299 species of aquatic mollusks — including present-day snails and slugs — over last five million years.

“The reason we picked the Western Atlantic as a study area is because we have excellent large datasets recording [the] distribution of both fossil and living mollusks from this region,” Luke Strotz, the lead author of the work, said in a statement. “I used a lot of fossil material from collections around the U.S."

They delved into the occurrences and extinction of different species over the said period as well as their respective metabolic rates or the amount of energy each of the creature in question needed for survival.

Much to everyone’s surprise, the findings of the work revealed that metabolic rates make a reliable factor for predicting the likelihood of extinction of a certain animal species or community of species.

"We found a difference for mollusk species that have gone extinct over the past 5 million years and ones that are still around today,” Strotz added. “Those that have gone extinct tend to have higher metabolic rates than those that are still living. [Meanwhile,] those that have lower energy maintenance requirements seem more likely to survive than those organisms with higher metabolic rates."

While other factors also play a role in determining the survival of a particular animal, this work does suggest that metabolism rates should be taken into account while forecasting which animals are more likely to go extinct in the future. This way scientists could better understand the mechanisms driving extinction, particularly in the wake of problems like global warming.

"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," study co-author Bruce Lieberman said in the same statement. "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.'"

Despite the extinctions over millions of years, the average metabolic rate of species remained largely unchanged over the 5 million-year-long period. However, the team did note that high-metabolic rates were a better indicator of extinction when the animals were endemic to a small region.

"Range size is an important component of extinction likelihood, and narrowly distributed species [with high metabolic rate] seem far more likely to go extinct,” Strotz concluded. The researchers think the results of the study are applicable to other marine animals, but further studies are still needed to understand if this is also the case of those living on land.

Arcinella cornuta Arcinella cornuta was included in a new large-data study of fossil and extant bivalves and gastropods in the Atlantic Ocean that suggests laziness might be a fruitful strategy for survival of individuals, species and even communities of species. Photo: Neogene Atlas of Ancient Life / University of Kansas