As Buck evolves into a creature of the wild, he discovers long-buried instincts that have been dormant for generations. In The Call of the Wild, London highlights the almost mystical qualities of Buck's nature that allow him to thrive in completely unfamiliar environments. London implies that Buck does more than just adjust; he accesses his ancestral memory to shape his actions.

It is this metaphysical aspect of Buck that has led critics to identify a supernatural or spiritual theme in the novel. Although Buck's journey drives him toward wildness and away from civilization, his encounter with Thornton pulls him back towards a domesticated existence. Thornton provides protection and nourishment, treating Buck as a beloved family member rather than merely a dog or working animal. During his time with Thornton, Buck's growing awareness of his ancestral memory draws him closer to the wild. The "call of the wild" thus represents the mystical natural forces within Buck, infusing the story with a supernatural element.