Some are cleverly animated (in various styles), others acted out in terms that range from the satiric to the tragic. The non-cartoon segments are primarily acted out by an appealingly goofy, vulnerable if muscled-up (from his juvenile TV stardom days on "The Rifleman") Johnny Crawford, and pert young Victoria Principle. (Stills from her nude scenes here were much later exploited as bogus evidence of a past "softcore" career after she'd achieved fame in the TV series "Dallas.")
"The Naked Ape" is imagined in creative and narrative ways that would never happen again (at least with a generous budget) after the mid-70s. It's conventionally sexy/humorous on the surface. But the overriding message is that the sexes should respect one another, and that mankind's tilt toward warring, macho self-destruction is anything but "natural." It's a beautiful message, one that the film arrives at with an entirely appropriate weight of melancholy and anti-Establishment critique.
A lot of counterculture-relic features from this era have dated badly, but I think this movie--poorly appreciated in the first place--is still forward-thinking, and would earn a larger cult following (the existing one flows from "cut" early-80s TV broadcasts and bootleg videos) if it were released as a legitimate DVD. C'mon, Hugh...this was your baby once, why not let it take some long-delayed toddling steps toward the public?
(P.S.: Looking at this review a decade later, I noticed the only two other "user comments" are from one person who erroneously thinks the original book was a "novel," and the other from someone who obviously hasn't seen the movie at all. Yeesh.)