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Despite the abundance of sea grass and algal beds, most marine mammals (except manatees) do not use them as a food source and have turned to carnivores. According to the researchers, the reason for this is probably the need for higher temperatures for the digestive enzymes of plants and algae.
Most cetaceans, such as elephant seals and manatees, live in warm waters. The only cold-water herbivorous mammal was the Steller’s manatee, which became extinct in the 18th century. This species was up to 10 times heavier than the current species.
Life in the water requires a water-sliding motor system, which leads to the shrinking of the motor organ and, as a result, the inability to move the body on land. Shrinkage of locomotor organs in whales and dolphins is associated with non-expression of several regulatory genes.
The process of eliminating features as complex as legs due to millions of years of natural selection pressure and random mutations is simply not reversible.
The researchers write in their article:Dullo’s Law It states that in the process of evolution, when a complex organ is lost, it cannot be regained. As seen in birds that have lost their ability to fly.
This does not mean that it is impossible to re-form structures with similar functions; But as the complexity of a feature increases, the probability of its evolutionary inheritance is greatly reduced, because the genes associated with it have changed or disappeared.
The University of Freiburg’s research group writes: “Inability to compete with current terrestrial carnivores, which are able to make optimal use of their locomotor organs on land and can pursue prey, could make it impossible for aquatic mammals to return to land.”
A comical attempt by crawling dolphins to prepare for an attack on the beach will simply be foiled by smarter predators.
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