A philosophical burlesque, Human Nature follows the ups and downs of an obsessive scientist, a female naturalist, and the man they discover, born and raised in the wild. As scientist Nathan trains the wild man, Puff, in the ways of the world - starting with table manners - Nathan's lover Lila fights to preserve the man's simian past, which represents a freedom enviable to most.

The film's title is borrowed from a Dani fable that Gardner recounts in voice-over. The Dani people, whom Gardner identifies mysteriously as "a mountain people," believe that there was once a great race between a bird and a snake, which was to determine the lives of human beings. Should men shed their skins and live forever like snakes, or die like birds? The bird won the race, dictating that man must die. The film's plot revolves around two characters, Weyak and Pua. Weyak is a warrior who guards the frontier between the land of his tribe and that of the neighboring tribe. Pua is a young boy whom Gardner depicts as weak and inept.