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The origin and evolution of whales: Where do whales come from as mammals? Why are hippos related?

Time:2023-03-27 05:19:12 author:Zoo Read:191次
The origin and evolution of whales: Where do whales come from as mammals? Why are hippos related?

Scientists have reached a consensus that cetaceans are not the ancestors of land mammals, they are actually descendants of land mammals. It can be seen from its structural characteristics: the forelimbs of cetaceans are very similar to those of land mammals, and the bones of the forelimbs of cetaceans are almost identical to those of human palms; when cetaceans swim, the spine moves vertically up and down, which is consistent with Cat and dog mammals on land run very much alike. In addition, cetaceans also breathe air through their lungs and surface at regular intervals. Some cetaceans, like land mammals, still use their pelvis to breed offspring. So when did cetaceans enter the ocean to live? 329 years ago, biologist John first proposed the conjecture that whales are not fish, but mammals. In the early 1880s, scientist Henry further perfected the above speculation. Whales retain many of the same characteristics as land mammals. Whales are mammals. The descendants of land mammals are not the ancestors of land mammals. At the same time, scientist Ferlauer believed that whales and ungulates must have a direct connection; Darwin, who proposed the theory of evolution, expressed his opinion in the late 1850s: cetaceans are actually descendants of ancient bears, but they have been widely criticized by public opinion. Criticized, as a last resort, he withdrew his conclusions. In 1900, biologists Eberhard and Charles proposed that cetaceans were the direct descendants of a long-disappeared carnivore, Schizodont; then, marine biologist Matthew proposed that the ancestors of cetaceans may be Primitive insectivore. The modern view on the origin of cetaceans was formed around 1990. Scientists Waring and Saree proposed that the tooth characteristics of whales are very similar to those of Mesculoptera, an extinct carnivore with hooves. It looks very similar to a wolf. Like whales, midclaws have distinctive triangular teeth, and their slender snouts and other features are very similar to those of whales. For these reasons, Waring and Saree believed that the ancestors of cetaceans were mesoclaws. At the beginning of the 21st century, scientists discovered the fossil of a whale in Pakistan. Through the study of ancient whales in Pakistan, it was found that the ancestor of whales was not a mid-clawed beast, but an artiodactyl animal, such as cattle, camels, hippos and other creatures. distant relatives. This cloven-hoofed animal departed from the mid-clawed animal many years ago and entered the sea from land. The ancient whale is a relatively primitive cloven-hoofed carnivore, and it also retains many of the characteristics of the cloven-hoofed animal, while the modern cloven-toed ungulate has been lost. these characteristics. Scientists have found that early hoofed mammals were carnivorous or scavengers, while today's cloven-hoofed or odd-hoofed animals have evolved to become vegetarians, but whales have retained the carnivorous characteristics of their ancestors. Whales are warm-blooded creatures and need high heat from their food to survive in the icy deep sea, so they retain their carnivorous characteristics. In the mid-1980s, American paleontologist Vincent determined that cetaceans were most closely related to hippos after comparing the DNA of several animals. Scientists have found that about 60 million years ago, hippos and whales had the same ancestor that lived in the sea. But one population of this creature ended up in the ocean as a whale, while another became a carbon beast, a direct descendant of the hippopotamus. The picture is from the Internet, and it must be deleted if it is infringed.


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