Complex sentence: The Caucasoid race refers to one of five racial categories of the physical anthropologist Carleton S. Coon, the other four races he defined were the Mongoloid race, the Australoid race, the Negroid race and the Capoid race.
Split into simpler sentences: The Caucasoid race is one of five racial categories as defined by the physical anthropologist Carleton S. Coon. The other four races that Coon defined were the Mongoloid race, the Australoid race, the Negroid race and the Capoid race.