The Expression of the Emotions in Man and Animals usually been viewed in its relationship to Darwin's conception of "natural selection" as the central mechanism of evolutionary development, which he probably grasped some time around September 1838. These notes have a tentative and fragmented quality, especially in Darwin's descriptions of conversation with his father (a successful doctor with a special interest in psychiatric problems) about recurring patterns of behaviour in successive generations of his patients' families. Darwin was anxious about the materialistic drift in his thinking – and of the disrepute which this could attract in early Victorian England – at the time, he was mentally preparing for marriage
Darwin from Descent of Man to Emotions our work; and of these you rank as the first." With "the little strength left in me" he reopened his enquiries into earthworms, requesting information from correspondents. The 6th edition of "Origin of Species" was published by Murray on 19 February 1872 at a price kept down to 7s. 6d. by using minute print, and sales increased from 60 to 250 a month. Through the spring Darwin pressed on with "The Expression of the Emotions in Man and Animals", pointing to shared evolution in contrast to Charles Bell's "Anatomy and Physiology of Expression" which claimed divinely created muscles to express