Why do people on Earth have different skin tones?

Because there is melanin under the human epidermis, he distributes melanin to various organs according to the various physique genetics of people, less is white, more is black, and melanin can also affect the color of human hair and eyes, hehe, this is what I saw on TV, hope.

The living environment is determined, and organisms are constantly changing their own structure and skin color according to natural conditions to adapt, which is the theory of evolution, such as the ,...... of black people in the tropicsLike Russia, you look at all whites.

The genes are not the same! The elementary party passed by - but it seems to be true.

The sun shines on different levels of intensity.

People with different health conditions have different skin tones, and there are very obvious differences in skin color between different races. Yellow people have a pale yellow complexion; Black people have dark complexions; Caucasians' skin tones are light and pale in color.

01 Scientists have found that there is no difference between human ancestors at the beginning, and their skin color is basically the same. It was only later that people moved to different regions and gradually developed differences in skin color in order to adapt to the outside world or environment.

The color depends on a chemical called melanin. The more melanin you have, the darker your skin tone. A light-skinned person who stays in the sun for a long time will produce a large amount of melanin, in other words, the person is sunburned.

People with albinism do not have melanin in them, and their color is usually pink, which is actually the color of blood through colorless. Usually, the hair of people with albinism is also white. Therefore, people with albinism have gray hair since childhood.

Melanin is the umbrella of the best. The ultraviolet rays in the sundry mountain can cause sunburn** and even lead to**cancer, melanin is like sunscreen, which can absorb the ultraviolet rays in the sun and protect ** from further damage. The more melanin in you, the darker your skin tone and the better your ability to absorb UV rays.

The color of human beings is the result of adaptation to nature in the process of evolution. Africans living in the equatorial region are often exposed to strong sunlight and produce a large amount of melanin in their bodies, so Africans are black. In the alpine land, there is less light, so ** is white.

Yellow people generally live in temperate regions, the intensity of sunlight is in the middle, and melanin is also in between, so the color of ** is also between the two people.

In summary, there was no difference in the ancestors of human beings at the beginning, and the skin color was basically the same. It was only later that people moved to different regions and gradually developed differences in skin color in order to adapt to the outside environment.

Because the content of melanin granules is different at the stage of development.

In the middle and lower part of the epidermis of the human body, there is a type of melanocyte. These cells contain melanin granules, which synthesize and secrete a brownish-black substance called melanin, which gives a person a certain skin tone.

The density of melanocytes in every part of the body is roughly the same in all races of the world, but due to genetic and environmental influences, the degree of development of melanocytes in melanocytes varies from race to race.

The development of melanin granules can generally be divided into four stages: the first stage is a spherical vesicle; The second stage differentiates into ovoid organelles; In the third stage, a certain amount of melanin is produced; In the fourth stage, the melanin granules have been completely blackened.

The reason why the skin color of the Caucasian people in Europe is white is because the melanocytes of the European mortars contain only a few melanin granules of the fourth stage, but there are a certain number of melanin.

The second and third stages of melanin granules, so their ** is whiter. Asian melanocytes contain moderately melanistic sections.

The third and fourth stages of melanin granules, therefore, they ** are yellow and brown. The black melanocytes of Africa are usually filled with stage 4 melanocytes, and their ** is also darker.