In Brave New World, people aren’t born; they’re created. After an in-vitro fertilisation, the embryonic cells are subjected to an array of treatments designed to hinder their development, including near-fatal doses of alcohol, x-rays, and extreme temperatures. But in this fictional world, the embryos react by splitting in two instead of dying. This means that the government can create as many as 96 embryos from one cell, making the process of making new workers exponentially more efficient. However, this process has some drawbacks.

With each successive treatment, the embryos develop traits that seem similar to those of Fetal Alcohol Syndrome. FAS is a disease that develops in babies exposed to alcohol in-utero; and there are a multitude of negative physical and mental defects. This is where the caste system in Brave New World comes from. Alphas and Betas are unique. They have no clones, because it’s necessary for them to be smart. Gammas have only been bokanovskified a few times, while Deltas have been through the process more, and Epsilons have been through it the maximum number of times.
The more times the embryos are bokanovskified, the stronger their symptoms become. They become less intelligent and shorter. This is, in fact, what the BNW government wants; a drawback for us is a benefit for them. Why does a menial worker need to be able to think? Why should an embryo destined to be a factory-line employee be intellectual? In such a utilitarian society, there’s no reason for that. In our society, the general consensus is that everyone deserves the best life they can get. In Huxley’s alternate future, it just isn’t so.