During the 20th century, anthropology developed following influential people such as Boas. The four subfields have long existed as separate fields, but with the direction of examining human culture in the United States, it has become important to be holistic. Each subfield has contributed greatly since no field can study the full breadth or depth of culture and behavior. However, there are forces that contribute to each field going in its own direction, which can lead to disintegration in the future. First, the emphasis on profession has led others to focus and specialize in their own perspective. Each field also has a greater difficulty in being expert in all four subfields when there are alliances with other disciplines that relate more specifically to their specialization. Finally, there always seems to be a gap between science and the humanities which has led to constant tension within anthropology, which sits at the border. One of the reasons for the creation of the four-field approach in anthropology is the study of Native Americans, who were seen as endangered (Darnell 2002:1). John Powell, for example, studied Native Americans through ethnological and linguistic means, and later created a Division of Mound Exploration (Patterson 2001:37, 39). Powell was also influenced by the evolutionism of Spencer and Darwin while studying Native Americans, and then influenced much of professional anthropology through publications of field investigations and researchers from different fields (Patterson 2001:40). However, the actual development of anthropology as a four-field approach occurs during the Boas period and when anthropology became a profession. Anthropology became a professio...... middle of paper ......, Bloomington.Little, Michael A. 2010 Franz Boas's place in American physical anthropology and its institutions. In Histories of American Physical Anthropology in the Twentieth Century, edited by Michael Little and Kenneth Kennedy. Lexington Books, Lanham, MD.Little, Michael A. and Kenneth A. R. Kennedy2010 Introduction to the History of American Physical Anthropology. In Histories of American Physical Anthropology in the Twentieth Century, edited by Michael Little and Kenneth Kennedy. Lexington Books, Lanham, MD.Moore, Jerry2012 Visions of Culture: An Introduction to Anthropological Theories and Theorists. 4th ed. Altamira Press, Lanham, MD.Patterson, Thomas2001 A Social History of Anthropology in the United States. Berg, Oxford.Trigger, Bruce2006 A history of archaeological thought. Cambridge University Press, Cambridge.