Emotion in animals specialised form of Occam's razor used in ethology, in which he stated: Charles Darwin initially planned to include a chapter on emotion in "The Descent of Man" but as his ideas progressed they expanded into a book, "The Expression of the Emotions in Man and Animals". Darwin proposed that emotions are adaptive and serve a communicative and motivational function, and he stated three principles that are useful in understanding emotional expression: First, "The Principle of Serviceable Habits" takes a Lamarckian stance by suggesting that emotional expressions that are useful will be passed on to the offspring. Second, "The Principle of
History of beliefs about the human body as imbalances of the 4 fluids of the body. Aristotle was unable to dissect humans but did so to many animals and was a early founder of comparative anatomy. Aristotle did contend quasi spiritual manifestations of the body principally through sexual distinctions. He wrote that the sex of humans: “is determined by the male principle already contained in the semen. If this is not strong enough, then the opposite must necessarily come into existence, and the opposite of man is woman.” Aristotle clearly superimposed man as the more important figure in men and women but presents an almost Qi like