The unified category white is in some respects a recent invention. Psychometric and anthropological literature published before World War II almost always broke European populations into smaller ethnic distinctions. In this earlier literature it is not uncommon to read about the Nordic, Alpine and Mediterranean races or to see tables showing the IQ scores of different European immigrants to the United States. Sarich suggests that the existence of races is almost self evident. But when we look at how race has been constructed in the popular mind and in the law we find only a system of folk taxonomy.
Human variation is a legitimate area of scientific study.
But the term race with its connotation of Platonic typology is not a suitable framework for this study. Certainly some of the variation in our species is the result of adaptation to local selective forces and barriers to gene flow do exist. These barriers include geographic isolation and cultural differences. But people travel and cultures change. Barriers to gene flow are continuously being breached and reconfigured.