Final answer:
The eugenics movement was a pseudoscientific practice that sought to improve human genetics by encouraging reproduction among people with desirable traits and reducing it among those deemed 'unfit'.
Step-by-step explanation:
The eugenics movement is a historical phenomenon that refers to the pseudoscientific practice of improving the genetic quality of the human population by encouraging the reproduction of people with desired traits (positive eugenics) and reducing reproduction among people with undesirable traits (negative eugenics). It gained notoriety with Nazi atrocities and has influenced modern debates on genetic engineering ethics. This concept gained popularity in the early 20th century and was applied in extreme ways by Nazi Germany, which led to the forced sterilization and massacre of tens of thousands under the guise of creating a superior Aryan race. The movement has since been discredited due to its unethical nature and the atrocities committed in its name, but discussions on genetics and selective breeding continue, highlighting ethical concerns in modern medical and reproductive technologies.