Eugenics was proposed as a means to selective breeding and genetic engineering in order to make human beings fit to survive in the world of the fittest, or in what is known as social Darwinism. The definition of eugenics is itself a much controversial subject. While some scholars think altering the gene pool is what is eugenics, some argue even attempting to alter some behavioral traits is also eugenics. While eugenics has got a bad name because of its association with the Nazis, who wanted to rid the world of anti-semitists through eugenics (Kelves, 1985, Proctor, 1988), modern day genetic and psychological intervention attempts to improve the quality of life (Kaye, 1997).
In the 1930s, the advances of genetic science induced many thinkers to be wary of the science trying to shape the nature of life. At the same time, the market system that mechanized the society was also coming into existence. Huxley's depiction of the "new world" follows the genre of literature that was repulsed by both. Although Huxley does not use the expression genetic engineering or eugenics in Brave New World, he describes the production of humans outside the mothers' womb in a manner that would match society's needs. Through biological conditioning, comprises addition of chemicals or rolling the bottles for making the embryos adjust to the levels of force, brains, and skills, the state creates a society that it wants. After the humans are "decanted" from the bottles - that is, after they were born - humans underwent the second stage of conditioning, that is, mentally conditioned, by hypnopaedia or sleep-teaching through which the society is continuously being programmed.
Brave New World describes a smooth form of tyranny through genetic engineering and psychological conditioning that creates a caste system, composed of a smart administrative class and a group of senseless serfs trained to love their tedious work, through control of the birth process and use of soma, a drug granting immediate ecstasy with no side effects. In effect, Huxley portrays a world in which a eugenically conserved class system maintains an inert society that grades its members from Alpha to Epsilon, and under-nourishes the embryo in the machines to make certain that Epsilons, for example, are underdeveloped and moronic, suitable for the tedious tasks that they are made to do. Through tapes played in dormitories at night, the state makes sure that people are glad with their rank, the ecstatic drug soma driving out the repulsive feeling.
In Brave New World Revisited, Huxley takes up the issue of science once again but in a more pragmatic manner. He depicts genetic intervention not as a stereotype of a racist eugenicist but as a prophet who would like to apply the theory for the advancement in an all-inclusive manner. He now feels that advancement of medical science, like for example anti-malaria medicines, does not benefit humanity at the end if it is counteracted by a problem of overpopulation and genetic bias. An increase in life expectancy is met with the challenge of having more people "cursed" by some genetic shortcomings. Despite the invention new therapeutic drugs and better treatment, the physical health of the general population may not progress, and may even get worse.