An example of this is that white people were plantation owners and black people were slaves. People who believe in racism also assume that because of peoples certain physical characteristics that make them a certain race they have certain personal characteristic that correspond with these physical traits. The truth is that people's bodies look the way they do is because their ancestry has adapted to their certain geographic location. It has nothing to do with their biological composition.
The lesson really caught my attention because of how surprising it was to learn how much I did not know about the subject. About peoples different characteristics and their surroundings over thousands of years. That the amount of melanin in a persons body is due to how close to the equator they live. It is all very interesting.