Zaius was one of the only apes in the city who knew that a human culture predated the time of the apes, a fact he eventually confronted his nemesis, Colonel George Taylor, with. Zaius also was well aware that ancient humanity was responsible for it's own destruction. As he said, humanity's madness walked hand in hand with its genius. For that reason, Zaius diligently kept the devolved remnants of humanity in a state of mute savagery and refusing to let them grow and prosper. Upon meeting the astronaut Colonel George Taylor, Zaius was horrified to see a human who could talk like an ape.
Although Taylor attempted to explain his origins, Zaius regarded him as nothing more than a mutation. Along with two others, he officiated at Taylor's inquest and determined that he had no rights under ape law, and that he was to be executed. Taylor later escaped custody and Zaius led a contingent of gorillas to track him down. Taylor captured Zaius outside of the Forbidden Zone and forced him to call off the hunt. A short time later, Zaius discovered that a true mutant community was discovered living in underground ruins in the Forbidden Zone. Along with gorilla military leader, General Ursus, Zaius led an expedition into the Forbidden Zone where he once again encountered Taylor. The mutants had in their possession a leftover relic of the 20th century, the Alpha-Omega Bomb. The bomb was activated and nearly everyone on the planet including Zaius were killed.