The selective breeding of humans as "alphas", "betas", etc. may have been inspired by the eugenics movement[1], which had prominent supporters in the U.K. at the time (e.g., Winston Churchill).[2] Except that in the novel, instead of just getting rid of "inferior" people, they actively bred them into a servant caste. (After Hitler gave eugenics a bad name, it became much less respectable.)

[1] https://en.wikipedia.org/wiki/Eugenics

[2] https://en.wikipedia.org/wiki/Eugenics#Supporters_and_critic...