Why are people symmetrical?

From the appearance, people are generally symmetrical, and this symmetry should be the most important for balance! That is to say, it is more stable, and there are fewer innervation conflicts in various organs. In addition, some people think that symmetry is perfect (I personally think that because people are symmetrical, people like symmetrical things, so they think symmetry is perfect). In fact, people are not symmetrical, and the left and right sides of the human body are not completely symmetrical. A small experiment can prove this point: take a front photo of yourself, divide it into two halves according to the center line, and then restore it according to the left half and the right half respectively. The result will be two different portraits. There is no symmetry from the outside to the inside. If you carefully observe the people around you, you will find that there are many asymmetries in the human body. Most people's forehead, the left side is slightly larger than the right side, so the right cheek protrudes slightly forward. Some people's eyes, one big and one small; A double eyelid and a single eyelid. Some people have high eyebrows and low ears. The fetus is in the mother's womb and will naturally tilt to the right by the sixth month. People's spine bends to the right in the chest and tends to bend to the left in the waist, so the left shoulder is often wider and higher. Most people's right hand is longer than their left. In terms of length, weight and volume, the right leg also exceeds the left leg. No wonder walking blindfolded on the flat ground will naturally turn left after a while. When you walk in newly bought shoes, you often feel that the shoes on one foot are comfortable and fit, while the shoes on the other foot are not so comfortable. It turns out that people's feet are one big and one small, which are also asymmetrical. Human internal organs are also asymmetrical. Two thirds of the heart is on the left side of the median plane of the body, and 1/3 is on the right side. The left lung has only upper and lower lobes, and the right lung is divided into upper, middle and lower lobes. Most of the liver and gallbladder are on the right side of the body, and most of the pancreas and spleen are on the left side. The function of organs is also asymmetric. The most obvious example of functional asymmetry is the function of left and right hands. Most people are used to using their right hand. They write, eat and work with their right hands. There are also a few people who like to work with their left hands. Their left hand seems to be more important and effective than their right hand. They are usually called left-handed. Symmetry can give people the aesthetic feeling of perfect symmetry. The "three elements" of beauty are simplicity, symmetry and harmony. The symmetrical human body coincides with Huang Jinlv. From the appearance, the complex human body is so simple, while the simple human body is symmetrical everywhere. Do you think human body is beautiful? It is said that the word "symmetry" first appeared in the 5th century BC. Poliklitos, a famous sculptor in ancient Greece, put forward the ideal proportional relationship in sculpture in a book. Nature shows image symmetry everywhere, like human body, even birds, animals, fish and insects, which are mostly left-right symmetry. People's eyes, ears, hands and feet are lifelike, and the left and right halves are very symmetrical. In addition to left-right symmetry, there are so-called "axial symmetry" and "central symmetry". The navel is called the "golden section" of the human body surface and is an important body surface symbol. Without this sign, it would be much more difficult to divide the human body into two symmetrical halves. However, the human body is also a complex geometric figure, with points, lines, faces, triangles, circles and so on. In the details of the human body, it is not absolutely symmetrical. For example, some faces are half big and half small; Some people have big eyes and a small amount; Someone's eyebrows, one high and one low, one flat and one upturned; Some people's ears, one big and one small, one pointed and one round. Although some people look well-proportioned, careful observation can still reveal some asymmetries. Therefore, this asymmetry of the human body is everywhere and ever-changing.