It is important to remember that one of the major themes of this excellent short story is Naturalism, which was a group of writers that believed that human behaviour is determined by heredity and environment. In their work, these writers present human beings as subject to natural forces beyond their control. Throughout this story, the anonymous protagonist is shown to be arrogant and to completely underestimate the power and danger of nature. The dog, on the other hand, is shown to act as a foil to the man, being sensitive to nature and following his instincts. The dog does not believe foolishly that he can master the situation through the force of his own will. By giving the dog the last word in the story, London seems to be emphasising the fact that animal instincts are superior to human judgement in this situation. Note how the story ends:

A little longer it delayed, howling under the stars that leaped and danced and shone brightly in the cold sky. Then it turned and trotted up the trail in the direction of the camp it knew, where were the other food providers and fire providers.

Ironically, it is the dog, and not the man, who trots safely off at the end of the tale to the camp, where he knows there is food and warmth. With the contrast between the dog that is alive and well and the frozen corpse of the man, nature is shown to be utterly indifferent to human beings.