This chapter traces ideas of development interlaced with the Russian reception of nisus formativus in the eighteenth and nineteenth centuries and their response in the Soviet concepts of oligophrenia in the middle to end of the twentieth century. United by a focus on the transformations caused by damage and disease, as well as the capacity for language and abstraction, descriptions of monsters and studies of oligophrenia are positioned in a specific intellectual tradition of imagining deviation as a means of explaining evolution. I begin by outlining the ideas and contexts influencing the adaptationAdaptation of nisus formativus that were significant for Russian and Soviet understandings of mental abnormality, then focus on the Soviet scientific framing of oligophrenia as a primarily biological phenomenon, supported by its grounding in terms of human evolution.