Ploetz initially studied economics in Wrocław, where he founded a reading group with his friends Carl and Gerhart Hauptmann. The group’s plans also included establishing a socialist colony. Persecuted as a socialist, Ploetz fled to Zurich in 1883, where he continued to study economics as well as making the acquaintance of several socialists and social democrats. From Zurich, Ploetz traveled to the USA to pursue his colony plans, returning six months later to study medicine in Zurich. There he was strongly influenced by the psychiatrist Auguste Forel, who advocated anti-alcoholism and women’s rights, while at the same time opposing racism and antisemitism; but Forel was also a eugenicist who was in favor of castrations and sterilizations.
Ploetz obtained his doctorate in medicine In 1890 and married Pauline Rüdin, the sister of Ernst Rüdin – the man who was to become the leading ‘racial hygienist’ in National Socialist Germany. Ploetz moved with Pauline to Springfield (USA) in 1890, where they lived for the next four years in a kind of commune in which Ploetz attempted to implement his socio-political ideas. He increasingly departed from his earlier socialist ideals, however, adopting the view that a future society would have to be shaped according to the principles of Darwinism.
In his second marriage – he divorced his first wife in 1898 – Ploetz married the wealthy Anita Nordenholz and moved with her to Herrsching am Ammersee, where he acquired a large estate. In 1904, Ploetz founded the ‘racial biology’ journal Archiv für Rassen- und Gesellschaftsbiologie, and in 1905 established the ‘(Berlin) Society for Racial Hygiene’. He had used the term ‘racial hygiene’ in the first volume of his 1895 publication Grundlinien einer Rassenhygiene, which set out the basic principles of his theory. Ploetz understood ‘race’ to mean a group of people spanning generations and defined by their physical and mental qualities.
Unlike the usual meaning of the word referring to individual health, the concept of ‘hygiene’ here was used collectively: Ploetz claimed it was possible to speak of the ‘hygiene’ of a nation, of a ‘race’ in the narrower sense, or indeed of the entire human race. According to his ideas, the ‘Aryan race’ was the cultural race par excellence, and promoting it was tantamount to promoting humanity in general. Based on the notion of ‘racial hygiene’ – the word ‘Rassenhygiene’ was originally used in German for eugenics, the ‘science of good genetic quality’ – it was necessary to promote the ‘genetically healthy’ and reduce the ‘genetically sick’ in a given population.
His publications and the associations he founded established ‘racial hygiene’, as he understood it, as a scientific subject and teaching discipline at universities, bringing it to the attention of broader groups within society, especially academics, and helping to gain political traction for the ideas and proposals involved. Together with the psychiatrist Ernst Rüdin and the ‘hygienist’ Max von Gruber, Ploetz founded the ‘Munich Society for Racial Hygiene’ in 1907, which developed into the ‘German Society for Racial Hygiene’ in 1910. With these three ‘racial hygienists’ and the professor of ‘racial hygiene’ at the university, Fritz Lenz, Munich became an early center of the ‘racial hygiene’ movement alongside Freiburg and Berlin.
Regarding the Germanic tribes as superior due to their low illiteracy rate, Ploetz took a particular interest in the ‘Nordic race’, devoting himself to its supposedly necessary ‘rescue’ by founding various secret societies, including the so-called ‘Ring of Norda’ (1907). Within the ‘Society for Racial Hygiene’, these societies were to be core components of ‘Nordic-Germanic racial hygiene’, requiring commitment to the ‘Nordic idea’ on the part of their members. On his 70th birthday, August 22, 1930, Ploetz was awarded an honorary doctorate by the Faculty of Natural Sciences of the University of Munich: according to the certificate, this was in recognition of the fact that he was “an outstanding researcher and the most eloquent advocate of eugenics”.
He emphatically welcomed the National Socialist seizure of power and, together with Fritz Lenz, Ernst Rüdin and Hans F. K. Günther, became a member of the ‘Advisory Council of Experts on Population and Racial Policy’ set up in 1933 by Reich Minister of the Interior Frick. This expert advisory council was tasked with examining all relevant draft laws prior to adoption in order to assess their impact in terms of population policy and ‘racial’ policy and also determine to what extent they could be enforced. Appointed a professor by Hitler in 1936, Ploetz joined the Nazi Party in 1937. He was celebrated by the National Socialists as a pioneer of the so-called ‘scientific notion of race’.
