Today, we see whales swimming in the ocean, and there are many kinds. There are two kinds of whales, toothed whales and baleen whales. Toothed whales include fierce killer whales and lively dolphins, and baleen whales include the largest blue whales. These whales have a common ancestor.
50 million years ago, whales and hippos had the same ancestor. At that time, ancient whales still lived on land. Like hippos, pigs, cows, sheep and deer, they have even toes and belong to cloven-hoofed animals. They have a name called land whales.
The picture above shows the skeleton of a land whale. One day, the land whale jumped into the sea to avoid being chased by big wild animals. The newly launched land whales, like other quadrupeds, flopped on all fours and paddled with dogs. Land whales that can't run fast on land can swim slowly after entering the water. It can't catch up with its prey in the water, and mainly lives by lurking hunting.
Land whales that occasionally go into the water during the day and rest on land at night have a new name, called swimming whales. The body of a wandering whale that lives in the water most of the time changes gradually in the water. In order to speed up the stroke, the slender limbs began to get shorter, the small soles became bigger, and thin fins grew between the toes. In order to facilitate breathing, the nostrils of stray whales move upward from the tip of the nose, from the front of the eyes to the back of the eyes, until the highest point on the forehead. You don't have to look up and breathe in. As long as they float on the water, the whales can breathe horizontally, which greatly increases the efficiency of water activities.
In order to advance the water hammer, the tail of the wandering whale becomes thick and long. In addition, it also learned the butterfly stroke, which pushes its body forward by swinging its back up and down. Butterfly swimming is much faster than dog planing, and wandering whales are more and more adapted to marine life. Walking whales belong to a transitional form of ancient whales, which reflects the change of ancient whales walking back from land to sea.
The picture above shows the bones of a wandering whale. The stray whale stayed in the ocean and never returned to land, becoming a marine whale. The forearm of the marine whale becomes shorter, the unnecessary elbow and wrist joints become stiff when paddling, leaving only the flexible shoulder joint, and the forearm of the marine whale becomes a flipper. The pelvis, which supported the weight when standing, lost its position in the sea, and the pelvis of marine whales shrank smaller and smaller, completely out of the spine. The marine whale, which looks like a fish, has not learned to swing its tail from side to side, but it still inherits the butterfly stroke of the wandering whale, moves up and down, and abandons its useless hind legs.
The picture above shows the skeleton of a marine whale. Marine whales can hold their breath for more than 2 hours, and the nostrils growing on the top of their heads become sharp breathing tools. Every time a marine whale goes out for air, the high-speed gas will wash the water left near its nostrils into the air, forming a spectacular fog column.
The whale's nostrils move from the tip of the nose to the highest part of the body, which just reflects the adaptation process of whales from land to sea.