The lazy, unemployed couch potato could represent the next stage in human evolution, according to a new theory.
A study has uncovered a previously overlooked law of natural selection based on "survival of the slacker".
It suggests laziness can be a good strategy for ensuring the survival of individuals, species and even whole groups of species.
Although the research was based on lowly molluscs living on the floor of the Atlantic Ocean, the authors believe they may have stumbled on a general principal that could apply to higher animals and people.
The scientists carried out an extensive study of the energy needs of 299 species of extinct and living bivalves and gastropods spanning a period of five million years.
Those that had managed to escape extinction and survived to the present day tended to be "low maintenance" species with minimal energy requirements.
Molluscs that had gone the way of the dinosaurs and disappeared had higher metabolic rates than their still-flourishing cousins.
US ecologist professor Bruce Lieberman, who co-led the University of Kansas team, said: "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. 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'."
Molluscs were used for the study because of the huge amount of available data on living and extinct bivalve and gastropod species.
The team now plans follow-up work to see if "survival of the laziest" natural selection applies to other kinds of animals.
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Dr Luke Strotz said: "There is a question as to whether this is just a mollusc phenomenon.
"There's some justification, given the size of this data set, and the long amount of time it covers, that it's generalisable. But you need to look – can it apply to vertebrates? Can it apply on land?"
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