In the 19th century, the industrial revolution was spread out the entire Western Europe and North America. In 1859, Charles Darwin’s On the Origin of Species was published and his theory of evolution was almost worldwide known. This made people reexamine their behaviors from a new perspective. Darwin’s evolutionary theory laid the philosophical foundation for literary naturalism. Darwin created a context that made naturalism -- with its emphasis upon theories of heredity and environment -- a convincing way to explain the nature of reality for the late 19th century (Pizer, 2000:47).

Naturalism was first proposed by French writer Emilie Zola, who developed the acute social consciousness that considered men are controlled by heredity and social environment and was the product of his temperament in a social context. This gave a totally new way of thinking about the novel. In the influence of naturalism, temperament was more important than character; setting could not be separated from a naturalistic theory of environment, nor plot from theory of evolution (Pizer, 2000:48).

American naturalism had been shaped by the civil war, the social turmoil that greatly undermined the faith of earlier age, and by the teaching of Darwinism.

2.2 The Common Themes of American Naturalism
American naturalists in literature disregarded the comforting moral truth, while tried to achieve an economic classes who were determined by their heredity and living environment. In presenting the extremes of life, the authors sometimes revealed an inclination to the sensationalism of romanticism, but emphasized the world is amoral, and people had no free will, and destiny of lives are determined by heredity and environment. Life, in essence, becomes an arduous struggle for survival.

In some naturalistic novel, the narratives pull away from civilization and decadence towards the more savaged. While the naturalistic novel presumes the reality of revolution, degeneration and personal decline are followed. And such decay finds its equivalence on the social level, where the fate of the individual is often inseparable from a declining family or a new urbanized crowd (Pizer, 2000:48). Although naturalism was admittedly pessimistic, it seems to have an implicit optimistic element. This usually comes from the belief that was made explicit by Herbert Spencer: whereas the fate of the individual is limited and destined to end in death, the fate of the species is to move ever onward and upward in an evolutionary march toward greater perfection (Pizer, 2000:48).





3 Naturalism Presented in The Call of the Wild
The Call of the Wild is a definite, forthright narrative of the travails of the protagonist Buck, who finally returned to uncivilized nature, echoing with the call of the wild. The novel is clearly naturalistic in its vivid and detailed descriptions of the primitive and bloody brutality of the nature, the vicious competition among the peers and the merciless masters. Naturalism is fully presented in the tremendous changes of Buck and his final image of “super dog”.

3.1 The Covert Heredity in Buck
Buck used to be a talented and extraordinary dog of Judge Miller’s in the sun-kissed south, but he was a massive, strong, privileged dog with a rich coat of fur. He was neither house-dog nor kennel dog like any other in Judge Miller’s ground, and the whole realm was in his control. He seems to follow in the way of his father, a huge St. Bernard who had been the Judge’s inseparable companion. Although he lives a privileged and comfortable life during the four years in country, with sort of arrogance or superiority, he saved himself from becoming a tame housedog. Hunting and some other outdoor delights had hardened his muscles and kept down the fat.  
 
When he was sold to a rude stranger by Manuel, one of the gardener’s helpers, his usual life and destiny had been changed. He was controlled by a hard rope, transformed to the rail and closed in a container, and encountered a series of brutal and bloody treaties when he tried to protest. It was followed that he was transformed to the icy, snow-white north, gathered with some other peers in misery, witnessed the fierce battles among them, how to have a rest in snow, endless toil with hunger and thirsty and so on. All in all, the cruelty of nature was unveiling his ferocious and gloomy side in intense pace. Wang Xu explains, 自然主义在《野性的呼唤》中的体现(4):http://www.youerw.com/yingyu/lunwen_132.html