Some scientists spoke of three races of mankind: The Caucasian race living in Europe, North Africa and West Asia, the Mongoloid race living in East Asia, Australia, and the Americas, and the Negroid race living in Africa south of the Sahara. Other scientists had different ideas and spoke of four or five races. These ideas were popular from the late 18th century to the middle of the 20th century. Because these ideas belong to former times, they are called historical definitions of race or historical race concepts.