What continents are black, white and yellow people distributed in now? Analyze the reasons.

It is generally believed that in the process of their formation, they are first influenced by the natural environment. For example, in tropical areas, people's skin is mostly black because of strong sunlight, strong ultraviolet rays and high temperature to resist the damage of strong sunlight. The nose is also wider, which is easy to dissipate heat. Lips are thick, too. On the contrary, in northern Europe, people's skin color is generally lighter because of the cold climate, weak sunlight and weak ultraviolet rays. Conducive to physical development. A high nose and long nostrils can make the inhaled cold air "warm" in advance. At the same time, some people think that the reason why yellow people have "wind eyes" (double eyelids) may be related to the climate in the sandstorm area of Central Asia. It can be seen that the formation of early national characteristics has a great relationship with the influence of the environment. Of course, with the development of human society, the role of the environment on the human body is weakening.

In addition, the formation and development of human race is also related to heredity. For example (the Indian yellow race migrated from the Bering Strait by the Asian yellow race, and the Southeast Asian yellow race also migrated from the Asian yellow race), Africans' skin is black, which can be preserved in their descendants and still inherited when they migrate to America or other continents. Therefore, blacks who immigrate to the United States have similar signs to other blacks, but they are different from whites.