NATURE12 July 2023
https://www.sciencealert.com/sea-mammals-may-never-be-able-to-return-from-the-ocean
Sea cows are the rare mammalian herbivores that made the transition to being fully aquatic.(Gregory Sweeney/Moment/Getty Images)
Aquatic adaptations in mammals may be irreversible, according to a new study investigating the means by which more than 5,000 species transitioned from land to water.
Although the evolutionary journey of animals like whales and seals can ultimately be traced back to marine tetrapods that left the ocean for a life on land, roaming terra firma again isn’t on the cards for the descendants of those that have become mostly or fully aquatic.
By comparing body mass, diet, and genomes of 5,635 existing and recently extinct mammals, University of Fribourg evolutionary biologist Bruna Farina and colleagues tracked the evolution of aquatic adaptations. These include changes in size, locomotion, sensory systems, reproduction, diets, and lung capacity.
Out of all those species 97 percent remain fully…
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