The Expression of the Emotions in Man and Animals Darwin notes the universal nature of expressions in the book, writing: "the young and the old of widely different races, both with man and animals, express the same state of mind by the same movements." This connection of mental states to the neurological organization of movement (as the words "motive" and "emotion" suggest) is central to Darwin's understanding of emotion. Darwin himself displayed many biographical links between his psychological life and locomotion, taking long, solitary walks around Shrewsbury after his mother's death in 1817, in his seashore rambles near Edinburgh with the Lamarckian evolutionist Robert Edmond Grant in 1826/1827, and
The Descent of Man, and Selection in Relation to Sex to the forces of sexual selection. While debates on the subject continues, in January 1871 Darwin started on another book, using left over material on emotional expressions, which became "The Expression of the Emotions in Man and Animals". In recent years controversy also involved the peacock tail, the most famous symbol of the principle of sexual selection. A seven-year Japanese study of free-ranging peafowl came to the conclusion that female peafowl do not select mates merely on the basis of their trains. Mariko Takahashi found no evidence that peahens expressed any preference for peacocks with more elaborate trains, such as