The evolutionary perspective has long influenced the study of anxiety. For modern Evolutionary Psychiatry, anxiety disorders are nothing else than pathologies of the defense system. Although Sigmund Freud, throughout his career, was also interested in the evolutionary origins of the human mind, his contributions to the field have frequently been forgotten, based on the allegation that his evolutionary theory of psychopathology is founded on a discredited evolutionary mechanism: the "Lamarckian" idea of inheritance of acquired characteristics. The present study investigates the influence of Darwin over the Freudian concept of signal anxiety. It shows that the concept assumes that anxiety is an adaptive reaction to danger, an idea influenced by his readings of Darwin's "The expression of emotions in man and animals" (1872). Signal anxiety is adaptive not only because it prepares the animal to deal with danger through the mobilization of psychic energy, but also because it helps the anticipated detection of new occurrences of the state of danger. The "Lamarckian" use and inheritance law, and other so-called "discredited evolutionary mechanisms", such as theory of recapitulation, are extensively referred to by both Freud and Darwin