Abstract: Although Darwinism played a major influence upon Jack London's life and literary creation, Jack London was never confortable with evolution's unethical aspects. This article, with a focus on London's boxing literature, attempts to examine various ways London explores in his works in reconciling his belief in Darwinism with his conviction that the ethical process is the defining factor in human civilization and social progress. His four works on boxing provide substantial evidence of development in his thoughts on Darwinism. In “The Game” at the same time that London demonstrates how Darwinian notion of “survival of the fittest” governs the reality of boxing, he shows his awareness of the ethical difficulties inherent in boxing. The influence of Darwin is also apparent in “A Piece of Steak”, but from the description of Tom King's miserable life and of his tears when losing the game, it is clear that London builds his sympathy for the old and weak boxer. London's later works such as “The Mexican” and “The Abysmal Brute” reflects his revisit and revision of his views on the Spencerian position of social progress. In “The Mexican” the game between Rivera and Danny is presented more like a parody, or in other words, a criticism of social Darwinism, as Rivera the physically weaker one wins the game and proves himself to be more “fit” than Danny by his devotion to Mexican revolution and moral superiority, other than by physical strength and boxing skills. “The Abysmal Brute” demonstrates London's departure from simple notions of social Darwinism. Joe's exposure of the corruption of boxing and his subsequent decision of giving up this career could be interpreted metaphorically as Joe's first ethical choice in his development from “a natural being” to “a social being.” It is in this sense that the text demonstrates London's increasing commitment to ethics and his belief in the cultivation of individual ethics as differentiating human beings from other living beings.