Emotion in animals teeth in aggressive action. A domestic dog's simple tail wag may be used in subtly different ways to convey many meanings as illustrated in Darwin's "The Expression of the Emotions in Man and Animals" published in 1872. Evidence for emotions in animals has been primarily anecdotal, from individuals who interact with pets or captive animals on a regular basis. However, critics of animals having emotions often suggest that anthropomorphism is a motivating factor in the interpretation of the observed behaviours. Much of the debate is caused by the difficulty in defining emotions and the cognitive requirements thought necessary for animals
The Expression of the Emotions in Man and Animals initial correspondence with the psychiatrist James Crichton-Browne Darwin set aside his material concerning emotional expression in order to complete "The Descent of Man", which covered human ancestry and sexual selection. Darwin concluded work on "The Descent of Man" on 15 January 1871. Two days later, he started on "The Expression of the Emotions" and, on 22 August 1872, he finished work on the proofs. In this book, Darwin brings his evolutionary theory into close approximation with behavioural science, although many Darwin scholars have remarked on a kind of spectral Lamarckism haunting the text of the "Emotions". Universal Nature of Expression: