This book was written by Charles Darwin and published in 1872, and deals with how both humans and animals express emotions. It contains material that he gathered while writing his book on human evolution, The Descent of Man: The Concise Edition.
He states early on in the book, "No doubt as long as man and all other animals are viewed as independent creations, an effectual stop is put to our natural desire to investigate as far as possible the causes of Expression ... He who admits on general grounds that the structure and habits of all animals have been gradually evolved, will look at the subject of Expression in a new and interesting light."
He articulates three general principles which "throw light on the theory of the subject," namely, "The principle of serviceable associated Habits," "The principle of Antithesis," and "The principle of actions due to the constitution of the Nervous System."
Many of Darwin's observations are interesting, such as:
"(T)he essence of savagery seems to consist in the retention of a primordial condition, and this occasionally holds good even with bodily pecularities."
"The expression here considered, whether that of a playful sneer or ferocious snarl, is one of the most curious which occurs in man. It reveals his animal descent..."
"Blushing is the most peculiar and the most human of all expressions."
This book will interest students of Darwin, and of the development of evolutionary theory.