[单项选择] For most thinkers since the Greek philosophers, it was self-evident that there is something called human nature, something that constitutes the essence of man. There were various views about what constitutes it, but there was agreement that such an essence exists -- that is to say, that there is something by virtue of which man is man. Thus man was defined as a rational being, as a social animal, an animal that can make tools, or a symbol-making animal. More recently, this traditional view has begun to be questioned. One reason for this change was the increasing emphasis given to the historical approach to man. An examination of the history of humanity suggested that man in our epoch is so different from man in previous times that it seemed unrealistic to assume that men in every age have had in common something that can be called "human nature". The historical approach was reinforced, particularly in the United States, by studies in the field of cultural anthropology (人类学). T
A. the emergence of the evolutionary theory
B. the historical approach to man
C. new insight into human behavior
D. the philosophical analysis of slavery