How is the idea of "survival of the fittest" is used throughout the novel?

Survival of the fittest is defined by the idea that in the process of natural selection only the strongest on any species will survive. When we are introduced to White Fang he becomes the lone surviving cub of his litter. Later, he is without doubt the strongest and most feared of the dogs living in the Indian camp. White Fang survives countless circumstances because he is undeniably strong, intelligent, and able to adapt to countless different circumstances.