The Rise of Eugenics.

In the nineteenth century with the discovery of the Darwin theory eugenics was constituted (as first considered by Francis Galton) as a means to control the population.  The weak and the "feeble-minded" were especially singled out by eugenicists.  Positive eugenics advocated a system of selective breeding to build a superior race, while negative eugenics advocated euthanasia and extermination of the "unfit".  Eugenics ended with the defeat of totalitarianism following the Second World War. In recent times however, with the rise of genetic engineering,eugenics has been reconsidered and with an increasing population, eugenic measures may come to take effect.

(It is of interest to note that eugenic measures were predicted in the nineteenth century by science fiction writers such as H. G. Wells or Benson, a Catholic who predicted an apocalypse in which euthanasia was seen as a "merciful end" to the weak and unfit.)