Coelacanth evolved and appeared 377 million years ago. From the perspective of bone structure, it is similar to today's terrestrial vertebrates. Fins correspond to the limbs of vertebrates. The spine extends from the neck to the tip of the tail. They can breathe air. Because there are strong bones in the fins of the abdomen, they can live on land for a short time without the ocean. With the increase of this behavior, they are more and more adapted to the marine environment. Finally, one of them completely adapted to land life, some terrestrial vertebrates evolved, and others continued to survive.
The coelacanth was once thought to be extinct, but it was later found in some sea areas. Dolphins are marine mammals. They breathe with their lungs, which are similar to human lungs. However, the bone structure and fin distribution are not closely related to human limbs today, and they have not appeared on the earth for a long time, with a history of only tens of millions of years. Some of them are close to humans in behavior, because they have smart brains and high brain-body ratio. They are one of the smartest species on earth except human beings, but they are still far away from human beings, but the evolution of species leads to the same goal. Dolphins compete with other species by swimming speed and IQ without absolute strength.
The structure and function of life on earth are compatible. If the similarity of body structure between some species is high, it can indicate that the genetic relationship is closer. For example, at present, all mammals have similar internal organs, bone structures and embryonic development processes, which is the characteristic of coelacanth. Scientists believe that they are the ancestors of vertebrates today, and the rediscovery of the existing coelacanth is regarded as the greatest biological discovery in the 20th century. Although people should not forget their roots, it is better to focus on the present life.