What ultimately drives Buck to abandon civilization?

The choice that Buck ultimately abandons civilization is driven by the overwhelming call of his primal instincts. Throughout "The Call of the Wild," Buck undergoes a significant transformation as he reverts to a more instinctual state, responding to the wilderness's demands. This shift is catalyzed by his experiences in the harsh Yukon environment, where survival becomes paramount.

As he faces challenges that test his strength, adaptability, and instincts, Buck begins to recognize his true nature as a wolf and a survivor. The "call of the wild" symbolizes this deep, intrinsic connection to the natural world, pushing him further away from the comforts and constraints of his previous life as a domesticated pet. The realization that he is more aligned with his wild ancestry than with the civilized life he left behind ultimately drives him to embrace his primal self and step fully into the wild.