In The Call of the Wild, primitivity is presented as the authentic and dominant side of a being. Modernization and civilization, then, go against true nature. Primitivity is tied to ancestry and history; as Buck has dreams of mankind thousands of years before, he yearns to be a part of the wild world to which his predecessors belonged. Certain feral emotions are raised in Buck: the need to hunt, the desire to kill, his lust for leadership and dominance. In the end, these emotions win out over the compassion, love, and safety of the human world.
Although many of his actions in the wild demonstrate Buck's change as a character, his developing prowess and love for the kill serve as a basis for his new life.
Buck's love for Thornton is incompatible with his place in the wild.