However, though research on emotion is wanting, some important works have been done to illustrate the vast importance of emotions in the human experience. One of the first truly authoritative of these is The Expression of Emotions in Man and Animals , by Charles Darwin, which was published in 1886. Darwin, well known for his development of evolutionary theory, is not as distinguished in his other pursuits, psychology among them. He could very well be called one of the founders of modern psychology, and he is certainly one of the fathers of the biological perspective within psychology. His ideas and experiments influenced, and indeed are continuing to influence, many, many people within this field, especially now that the combination of genetics and emotion, of nature and nurture, is beginning to play more of a major role.
Expressions is set up as a biological, evolutionary look at emotions in humans and other animals.
Darwin systematically describes the expressions, functions, evolution, and theories behind each different, specific emotion. The currents that run through the work touch on the basic emotions such as happiness, anger, and fear, and then on to more obscure, almost pseudo-emotions like astonishment and meditation. As he describes the outward physical manifestations that make up each particular emotion, Darwin discusses various muscle movements and configurations of expression, as well as the evolutionary meaning behind them. Darwin's three principles, under which, he believes, all emotions operate, begin with the Principle of Serviceable Associated Habits. The dog is in a hostile frame of mind at this point, and so bristles his body for an attack upon his enemy.