First Appearance: Planet of the Apes (Pierre Boulle, originally published in French as La Planét de Singes)
Other Appearances: None
Biography: Zaïus was the leading orangutang scientist on the ape-dominated world called Soror. He headed the research institute. Zira informed Zaïus that she had discovered a human capable of thought and speech, but he didn't believe her. It is not until Ulysse Mérou makes an address to the ape masses that he's discredited in his belief that a man could not have a soul. “Mi” is an honorific in the ape language of Soror.
Miscellaneous: In the novel, Zaius is actually a minor character, without any dialogue at all! As you might have guessed, the original Boulle novel is quite different from the first Planet of the Apes film. The human protagonist, Ulysse Mérou, is quite different from George Taylor, and many of the apes in the novel, while having the same name as apes in the film, behave quite differently.