Modern racial categorization has its roots in genetics, which originate from Gregor Mendel's Laws of Genetics formulated around 1900. The principle of heredity was eventually applied to humans, and thus Racial Hygiene, or negative Eugenics, was born.

Racial scientists regarded the general population as a biological entity. They warned against letting the human genes deteriorate by allowing racially “inferior” individuals to reproduce, recommending sterilization in such cases. At the same time they called for creating conditions which would facilitate the propagation of “worthy” individuals. The racial scientists regarded race mixing and influx of “alien races” as a threat to public health and national culture.The photos displayed in the background are taken from one of Hans F. K. Günther’s highly influential books on Nazi eugenics, Kleine Rassenkunde des deutschen Volkes (published in several editions from 1928).