Although Scaroth and Azal had a profound influence on the development of mankind (see City of Death and The Daemons), the role of the Fendahl (Image of the Fendahl) was pivotal.

The Doctor says that its effect on evolution 'would explain the dark side of Man's nature'. He also offers an alternative explanation: 'the Fendahl fed into the RNA of certain individuals the instincts and compulsions necessary to recreate... through generations until they reached Fendelman and people like him.' The Doctor, however, admits that it could all be 'just a coincidence'.