Freud used the term phylogenesis to encompass the process of human evolution from its earliest origins. He hypothesized that individual development (onto-genesis) repeats the main stages of evolution, with the traumatic events in the history of humanity thus reappearing and having a structural influence on the individual. This would explain the universality of primal fantasies, the Oedipus complex, and, more globally, a general outline for the development and functioning of the human psychical apparatus (or psyche).