The pseudoscience of producing genetic improvement in the human population through selective breeding. Proponents often saw ethnic/racial minorities as genetically "undesirable" and inferior.

Eugenics

Explanation:

The effort to produce genetically improved humans through selective breeding arose in the 20th century as a way to improve the human race by encouraging the "desired and healthiest" (people deemed the fittest, according to their criteria) to have more children.

On the other hand, the ethical concerns rose since minorities or whole ethnic groups were seen as inferior and undesired to live in the world.

Perpahs the extreme of this came when the national socialist defended with similar arguments the idea of a human species the so-called "Arian race", that would ultimately be free of diseases, disabilities and most undesirable traits that humans were expected to leave behind.

Many of the beliefs of that time have been proben today to be false.