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 Variation of Animals and Plants under Domestication grown too long, & I think I shall publish separately a very small volume, 'an essay on the origin of mankind'". This "essay" would become two books: "The Descent of Man, and Selection in Relation to Sex" (1871) and "The Expression of Emotions in Man and Animals" (1872). The book had been advertised as early as 1865 with the unwieldy title "Domesticated Animals and Cultivated Plants, or the Principles of Variation, Inheritance, Reversion, Crossing, Interbreeding, and Selection under Domestication" but Darwin agreed to the shorter "The Variation of Animals and Plants Under Domestication" suggested by the compositors. By May he