Why do people have black and white Huang San people?

It's exposure to the sun. In layman's terms, the more people get sunburned, the darker they get. Look at the map carefully. Africa straddles the equator. Ancient people in China lived in the Yangtze River and Yellow River basins, between 30 and 45 degrees north latitude, while most parts of Europe were above 45 degrees north latitude.

The difference of light intensity in latitude makes the color of skin color different.

After the completion of human civilization, the traffic is developed and people are gradually dispersed, but people of different colors still gather in a certain area.