Anonim

When and under what thrusts did the largest animals on the planet reach their current size? The dilemma about the size of the blue whales (Balaenoptera musculus) and other giant cetaceans may have found a first answer. According to a group of evolutionary biologists at the University of Chicago, whale gigantism has accelerated dramatically over the past three million years.

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Lanky recently. "We think of whales as giant creatures, but if we consider the 36 million years of their evolutionary history, they have been so great for no more than a tenth of this period, " explains Graham Slater, among the authors. The researcher studied the fossils of 63 extinct whales and 13 living species with his colleagues. He compared dimensions and position in the cetacean family tree, elaborating computer models on how gigantism evolved.

More food, concentrated. Although the size of these animals has gradually changed over time, the exaggerated sizes of 10 meters and over (of blue whales and other whales) would have been reached only in the last 2-3 million years, probably due to the increase in cold water and nutrient dense in the regions around the continental shelves, due to the beginning of the glaciation in the northern hemisphere, about 3 million years ago.

The climatic phenomenon led cetacean food to concentrate in dense pockets, rather than distributing it uniformly in the seas. Giant animals with equally gigantic mouths can make the most of plankton reserves while they are there, and forfeit enough energy to swim to the next ones, which can also be found "months" away.