How many kinds of humans are there in the world?

The division of different races and the reasons for the formation of skin color

Black, yellow and white are the three primary colors of the human body. However, after tens of thousands of years of evolution, it now emits colorful light. Scientific investigation has confirmed that there are 60 different races on the earth today.

/kloc-In the 8th century, the Swedish taxonomist Linnaeus scientifically divided the systematic position of human beings. According to different skin colors, human beings in the world are divided into four major races: white Europeans, black Africans, yellow Asians and red Americans. The division of Linnaeus, especially the division of the system position of apes and the division of Homo sapiens, is very scientific and has been used to this day. However, the geographical division of his four major races is not perfect and accurate in the future application, because the geographical division of each continent and the distribution of ethnic skin color are not consistent. For example, Asians are not all yellow, Africans are not all black, and the distribution of whites is not limited to Europe. Indians with a large population are located in Asia, but their skin color may be darker than that of people in North Africa. Lapp is a deer herding tribe in Scandinavia, northern Europe, which is closer to the yellow race in Asia in color. As for the skin color of southern Europeans and people along the Mediterranean coast of North Africa, it is also difficult to distinguish clearly. Another example is the American red man, which is even more untrue. Native American Indians have similar skin colors to the yellow race. Archaeology has proved that their ancestors entered America from the Asian continent 20 thousand to 30 thousand years ago. As for the theory of red, it may be due to misunderstanding of the custom of Indians painting themselves with ochre in religious ceremonies when Europeans entered America. In today's America, there are not only Indians living in the same family as the yellow race, but also a large number of immigrants from Europe and a large number of African blacks. It has become a "new world" where people of all colors live together. The colors of residents are like the palette in the hands of painters, and it is difficult to distinguish them clearly.

In order to accurately divide the skin color of races, it is necessary to understand the law of skin color formation and uncover the mystery of skin color formation. A person's skin color is related to many factors, such as skin refraction, capillary distribution, blood flow and so on. But the most important thing is the pigment in the skin. Pigment is located on the pigment cells at the base of human epidermis. Under the microscope, pigments are tiny brown particles. The more and denser the pigment distribution, the darker and heavier the skin color will be; On the contrary, the less and thinner the pigment distribution, the whiter and lighter the skin color will be. According to statistics, the number of pigment cells in different skin colors is different. Within 1mm2, white people have about 1000 pigment cells, yellow people have about 1300 pigment cells, and black people have about 1400 pigment cells.

People's skin color has a stable heredity, and the skin has a certain primary color at birth. Even if the skin is exposed to the sun for a period of time, the pigment will increase, or the blood flow will increase because of blood vessel dilation, which will make the skin turn black and red, but it will return to its original characteristics after a period of time. It can be seen that human skin color is controlled by genetic material and has a stable genetic basis. At present, it is difficult to draw a clear conclusion about the genetic factors that control skin color, but the biochemical process of pigment production has been clear. The formation of pigment is mainly related to a protease called tyrosinase. Under its action, intracellular tyrosine can be converted into pigment components. Without this enzyme, pigment cells will lose their function and cannot produce pigment substances. If a person lacks the genetic factor produced by this enzyme in the genetic material obtained from both parents, he will suffer from pigment deficiency, that is, albinism. Due to congenital lack of pigment, the patient's skin and hair are white and his eyes are red because there is no pigment covering. According to the clinical statistics of genetics, one hereditary patient in about 20,000 newborns suffers from this albinism.

The role of pigment is to participate in protecting the skin. Pigment determines the color and hiding power of skin. It can prevent too much sunlight and ultraviolet rays from harming the body and prevent too much infrared radiation from reaching the deep part of the body. Therefore, the skin color of the human body is controlled by the internal genetic material, and at the same time it is also subject to the pressure and choice of the external sunlight. In tropical areas with strong sunshine, blacks with heavy pigments are more adaptable than whites with less pigments. Under intense photothermal radiation, white people have a higher risk of skin cancer. On the contrary, if dark skin color is a disadvantage in the cold north of the earth, relevant data prove that blacks are more likely to get frostbite than whites on the Korean battlefield. It can be seen that the change and distribution of skin color depth are related to the choice of external environment, and the production and activation of pigments are often inseparable from the stimulation and induction of the environment. For example, ultraviolet rays in sunlight are invisible short-wave rays, which can kill tiny cells in the human body, promote the production of vitamin D in the human body, and make alcohol substances (such as ergot, etc.) in the human body. ) under the action of ultraviolet energy, it can be converted into vitamin D, which can promote the absorption of calcium and phosphorus by human bone tissue, thus hardening bone development. If the lack of necessary ultraviolet radiation affects the production of vitamin D, it will lead to rickets and rickets. Therefore, in most parts of Europe that are often cloudy and cloudy, white people with lighter skin color are also a favorable adaptive feature. They can absorb enough ultraviolet rays from the sun to reduce the occurrence of diseases. When babies grow up, doctors often tell them to get more sunshine.

The change of human skin color depends on the change of pigment content in skin, and the change of pigment content is the result of long-term adaptation to external light intensity. It can be said that a person's skin color is the brand left by nature on the human body. On the earth, the changing trend of skin color distribution of different races and human pigment depth basically corresponds to the intensity of sunlight radiation. People with more pigments and darker skin are mostly concentrated near the equator of the sunny earth. As the latitude of the earth goes on, the farther away from the equator, the weaker the sunlight and the lighter the skin color of the human body. In Asia, South Asians are darker than North Asians; In Europe, too, southern Europeans are darker than northern Europeans.

The fact that ethnic colors change with the environment breaks through Linnaeus's method of dividing ethnic colors according to continents. 1775, that is, 40 years after Linnaeus put forward racial division, German natural anthropologist Blumenbach announced a new racial division scheme. Brinell divided the races in the world into five major races, namely, black race (originally called Ethiopian race), Mongolian race, Malay race, American race and Caucasian race. He replaced the original African blacks with black people (nigro is Latin, which means black). Black people include not only black people in Central and South Africa, but also black people in America and black people scattered all over the world. In recent years, it has been advocated that black race and Australian dark race should be collectively referred to as equatorial race. Brinell replaced the original Asian yellow race with Mongolians and Malays. Mongolian race includes China and Japanese in the north and east of Asia, but today people are still used to merging Malays into Mongolian race. The American race proposed by Brinell includes Native American Indians. In recent years, some people advocate that the Indian race and the Mongolian race should be merged to be called Asian-American race. Finally, Brinell replaced the Caucasians in Europe with Caucasians, including not only most of Europe, but also the Caucasians in North Africa, Southwest Asia and the Mediterranean coast.

Obviously, the racial division of Blumenbach has made great progress compared with the four major racial divisions of Linnaeus. But after Brinell, in order to accurately divide races, people added head type, nose type, blink, hairstyle, hair color and blood type to skin color. In the long-term practice of racial division, people feel that the greatest feature of human beings is the constant flow, which leads to the differentiation of national characteristics and the continuous integration of national characteristics. Therefore, it is still difficult to find a completely applicable and effective ethnic division scheme.