Race (sociology)

The term race or racial group refers to dividing the human species into groups. The most widely used human racial types are those based on visual traits (such as skin color, cranial, facial features, or type of hair). 
Modern biology says that there is only one human race. But the word "race" also has a meaning in sociology. Many people react in one way if they see a white person and in another way if they see a black person. That's why census forms sometimes ask people to describe their ethnic origin. It is a way of asking "what racial group do you think you are?".
History.
In the 19th century and in the early 20th century, many scientists divided human beings into three races. White people were called "Caucasoid race", black people were called "Negroid race", and the people of East Asia and Southeast Asia were called "Mongoloid race".
There was much prejudice in this way of looking at the world. The Europeans and Asians both regarded themselves as superior to the other skin colors. Racism, a non-scientific theory or ideology, was that a particular race was superior or inferior. It argued that in the races that make up the human race, there are deep, biologically determined differences. It also states races should live separately and not intermarry. A supporter of racism is called a racist. These attitudes supported the horrors of African slavery, Apartheid, segregation and the Jim Crow laws, Nazism and Japanese imperialism.
Recent genetic studies show that the skin color in a population may change a lot over as few as 100 generations, or about 2,500 years.
Social darwinism and race.
Social darwinism refers to the idea that competition is active among all individuals, or groups.
It is a social adaptation of the theory of natural selection as proposed by Charles Darwin. Natural selection explains success in animal populations as the outcome of competition between individuals and groups for limited resources. This idea is popularly known as "survival of the fittest", a term first used by Herbert Spencer.
Fascist movements have commonly held social Darwinist views of nations, races, and societies. In Nazi Germany, the Nazis used social Darwinism to promote their racialist idea of the German nation was part of the Aryan race and believed in the competition of races. The Nazis tried to strengthen the ‘Aryan race’ in Germany by murdering those they regarded as inferior. By this they meant Jews, Slavs, Roma, homosexuals and disabled people.