A major influence of the Darwinian revolution has been to emphasize the presence of continuities in natural phenomena where formerly only dichotomies had been seen. This chapter provides an account of how the influence of the shift has been and is affecting disciplines in which C. R. Darwin took an interest – developmental psychology and psychiatry. It shows how the belated introduction into these disciplines of Darwinian principles is enabling heartening progress to be made. The aim of Darwin’s study of the emotions in man and animals was as a test of his thesis that man has evolved as a species within the animal kingdom. In collecting his data Darwin relied on the systematic observing and recording of behaviour as it occurs in the natural setting. Since Darwin reached that conclusion much water has flowed under the psychological bridges. For a time radical behaviorism seemed too many to have relegated Darwin’s views to a prejudiced past.