The point I’m trying to making in all my work is this: “If we want to survive on this planet, we must listen to what our neighbors in the community of life have to tell us.” So. Who’s in the best position to speak for those neighbors of ours? One of US or one of THEM? Obviously one of THEM. The teacher in Ishmael had to be one of those neighbors — a nonhuman. Among those neighbors none is more impressive and authoritative than a gorilla (which is why I chose to make Ishmael a gorilla rather than, say, a parrot or a salmon or a butterfly).
If you were to ask the author of The Hunchback of Notre Dame why he made the bell-ringer a hunchback, he would tell you: “Because I hadn’t made him a hunchback, there would have been no novel.” The same is true of my book. If I hadn’t made Ishmael a gorilla, there would have been no novel, and you wouldn’t be here reading about it.
For anyone interested in studying this question more deeply, I highly recommend the monograph “Apes of the Imagination: A Bibliography” by Marion W. Copeland.