In the current Epoch, no matter how strong or weak other monsters are, they all basically belong to one race. Beastmen are different, however, because of the numerous branches they previously had, the process of evolving from bottom-level monsters to emperor-level creatures involved a change in identity almost every time they upgraded. From the initial state of Beastman to the later ordinary Beastman and Beastman royalty, until now, when Zhou Tian has reached this step, he has successfully evolved into a Behemoth, known as the Beastman Royal Family.
The constant change of their affiliated races greatly increased the difficulty for Beastmen like Zhou Tian to adapt to physical changes, but it also inadvertently provided them with more potential for growth.