Human uses of mammals that "one is well advised to study the behaviour rather than attempting to get at any underlying emotion". Charles Darwin however had accepted the idea of emotion in animals, writing his 1872 book "The Expression of the Emotions in Man and Animals" on the subject. Darwin believed that mammals had social, mental and moral lives. In "The Descent of Man" (1871), he wrote: "There is no fundamental difference between man and the higher mammals in their mental faculties." Biologists remained wary of the idea, even for the great apes, but this led to serious difficulties, as Donald O. Hebb explained
History of emotions historiographical approaches such as conceptual history, historical constructivism and the history of the body. Similar to the sociology of emotions or anthropology of emotions, the history of emotions is based on the assumption that not only the expression of feelings, but also the feelings themselves are learned. Culture and history are changing and so are feelings as well as their expression. The social relevance and potency of emotions is historically and culturally variable. In the view of many historians, emotion is, therefore, just as fundamental a category of history, as class, race or gender. A number of different methodological approaches