What are the speakers mainly talking about?

M: Lisa. [8A] Do you have any idea of race? What does race mean to you?
W: A running event.
M: Not that type of race. Think of different people.
W: Do you mean different types of people and different colors?
M: Good. Much closer. The idea of race started to become popular in the 19th century. "Race" was a concept important to the idea of origins and to the 19th century development of the science of biology. Physical differences between peoples were said to be explainable using the concepts of race or racial group. In the 19th century biologists suggested that each human came from one of three general racial groups. What do you think these groups were?
W: Hmm…white, black and Asian.
M: You have the right idea, just the wrong terms — Caucasian, Negroid and Mongoloid peoples. Physical differences were seen as results of the specific geographical origins of distinct peoples. Today biologists have little or no use for the terms race or racial. This is a result of the theory that all humankind, yes, I mean that everybody in the world originates from the same ancestors and from the same geographical location. Science also suggests that early humankind was nomadic and therefore the issue of the geographical "origins" of a group of peoples is inaccurate.
W: Oh, I benefit a lot from you today, and I’ve never thought of it before.