Differentiation occurred around the age of 10 to 14, called as First Puberty. Around that time, children will begin to develop their inherited rank characteristics. Alphas and Omegas will start to exude their basic scent (musky/woody for Alphas, vanilla for Omegas) , while Betas experience wet dreams for boys and periods for girls. 

Female Alphas and Male Omegas will also start to experience major changes in their body, especially their external ia. This will naturally happen if there are no outside factors such as early mating, where venom injected from an Alpha's fangs will act as an inhibitor to GnRH, and if the injection repeatedly occurred in a relatively short time, Female Alpha / Male Omega will not experience further advanced Differentiation and wasn't able to reach their full maturity at age 18. 

Usually, these failed Female Alphas and Male Omegas are called "Low Alpha" and "Low Omega" due to their inability to go into rut, heat, and produce ual pheromones. Expert placed their caste as any normal Beta, as Low Alpha could still get pregnant (though the chance was less than 5%) and Low Omega could still impregnate female Betas and Omegas.

But this term was misinterpreted by common people, leading to a split of the caste system. Now, Low Alpha and Low Omega were considered as Alpha and Omega who were born from Beta parents and while they "worth" more than Betas, they were considered as "oddity". Most chose to discard their Alpha-Omega rank and lived their life as one of the Betas.

Second Puberty occurred around the age of 17-19 and it was required for the entire population of South Korea to take a test to be formally recognized as an Alpha, Beta, or Omega. From this point onward, Alphas will experience ruts twice a year; 1-2 weeks after their birthday and around 5-6 months afterward, and Omegas will experience heats which occurred 3-4 times a year.