Despite taking place in a future society, Brave New World emphasizes the scientific theory and debates of the time it was written. As a child, Huxley dreamt of becoming a doctor, but he fell ill and instead turned to literature. When he wrote Brave New World, new understandings of genetic variation and evolution were coinciding with the development of medical technologies. Huxley was also heavily influenced by Charles Darwin, who published On the Origin of Species, a scientific text that was accessible to general readers, in 1859. Using evidence from his travels and research, Darwin argues that different species developed over time through a process called evolution. Brave New World reflects Huxley’s attempts to wrestle with the implications of Darwin's theory. Darwin theorized that humans, like other species, struggle to survive in a competitive environment by adapting different traits over generations. These adaptations, combined with reproduction, contribute to a wide variety of traits among people. Brave New World takes these conclusions to a new level: what if human beings could control the adaptation of different traits among human beings to make them better suited for particular environments? This question, which originates with Darwin's theory, drives the system of genetic manipulation in Brave New World.

While developments in evolutionary science were being published and accepted by the scientific community and the general population in the early 1900s, new research was exploring the frontiers of population control through medicine. From 1877 to 1927, a group in Great Britain called the Malthusian league worked to educate and gain support for methods of birth control and contraception. They believed that without some form of birth control, human populations would inevitably decline into poverty and conflict. Huxley picks up these threads and runs with them in Brave New World, demonstrating an extreme form of birth control: mass sterilization and the Malthusian belt. Women in Brave New World wear a Malthusian belt as a form of contraception. Instead of pregnancy, human beings are produced through Bokanovsky’s process. The director describes how “a bokanovskified egg will bud, will proliferate, will divide. From eight to ninety-six buds, and every bud will grow into a perfectly formed embryo, and every embryo into a full-sized adult. Making ninety-six human beings grow where only one grew before. Progress.” Through this process, population growth is controlled by the government.

In the years that followed the publication of Brave New World, a new movement called eugenics would seek to achieve similar controls over human variability and encourage widespread sameness on the basis of race. Those who supported this movement, including the Nazi party in Germany, used forced sterilization not to produce a new species, as in Brave New World, but to eradicate existing groups. Huxley's vision for the terrible possibilities of science and medicine taken to extremes is a useful framework for considering violence and warfare in the twentieth century. While exploring the possibilities of artificial genetic selection and population control, Huxley's novel serves as a warning to readers about the danger of scientific developments applied to human behavior. John's horror at the "nightmare of swarming indistinguishable sameness" makes it clear that this society has eliminated the possibility of human difference, resulting in a population that resemble mass-produced objects on an assembly line more than human beings. Brave New World offers a satire of the type of utopia one might envision through evolutionary control, but ultimately champions the human capacity for choice, agency, and diversity.