This thesis explores the intricate intellectual and ideological journey of George Montandon (1879-1944), a figure who defied easy categorisation in anthropology. Despite encountering various anthropo-ethnological movements and their influencers, Montandon remained on the fringes, always maintaining a singular and evolving position. His career was marked by attempts to revolutionize the institutionalization of anthropology and ethnology in Switzerland and France, characterized by his original and eclectic contributions and his memberships in the first half of the twentieth century. This eclecticism is evident in his ethnographic travels to Ethiopia and the Far East, his theoretical proposals such as German diffusionism and ologenesis, and his complex ideological shifts, first with communism and later with scientific anti-Semitism. Above all, this work seeks to qualify the teleological interpretation of Montandon's career. While it is true that the raciologist showed an early and particular interest in Jews, it would be intellectually and methodologically dishonest to reduce the reading of his biography to his anti-Semitic radicalisation. The study of his ethnographic travels also provides an example of the presence of colonial concepts in a country with no imperialist state ambitions, which has been conceptualised as colonialism without colonies, or Swiss imperialism. Whether Black or Ainu people, Montandon perceives these natives through a pre-existing discourse that is unfavorable to the former and advantageous to the latter. Finally, Montandon's years in France demonstrate the porosity between the new ethnology and “classical” anthropology. Although there are significant differences between these two movements, the boundary is not so clear-cut. Not only did Montandon frequent ethnologists and then conservative anthropologists, but several concepts, such as race and eugenics, also figured prominently with both. Montandon's journey over three decades, from amateur ethnography to collaborationist ethno-racism, was marked by a stark contrast between his initial aspirations and his eventual legacy. His hope to leave a significant mark on the ‘science of man’ through his partisan adherence and universalist theoretical proposals was overshadowed by his anti-Semitic speeches and actions. His post-mortem fame, primarily built on these actions, stands as a testament to the disappointment of his unfulfilled recognition, with his virulent and criminal anti-Semitism overshadowing all other contributions.