During the 20th century, anthropology developed following influential figures such as Boas. The four subfields have long existed as separate fields, but with the shift toward examining human culture in the United States, it has become important to be holistic. Each subfield has contributed greatly, as no single 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 could lead to a breakup in the future. First, the emphasis on the profession has led others to focus and specialize in their own perspective. Each field also has an increased difficulty in knowing the four subfields well when there are alliances with other disciplines linked more specifically to their specialization. Finally, there still seems to be a gap between science and the humanities, which has led to constant tension within anthropology, which sits on the border. One of the reasons for the creation of the four domain approach in anthropology is the study of Native Americans, who were considered endangered (Darnell 2002:1). John Powell, for example, studied Native Americans through ethnological and linguistic means, and later established a Mound Exploration Division (Patterson 2001:37, 39). Powell was also influenced by the evolutionism of Spencer and Darwin when he studied Native Americans, and later influenced much of professional anthropology through publications of field investigations and researchers in different fields (Patterson 2001: 40). However, the real development of anthropology as a four-domain approach came during the time of Boas and when anthropology became a profession. Anthropology has become a profession...... middle of paper ......, Bloomington.Little, Michael A. 2010 The place of Franz Boas 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 AR 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.