Survival of the Fittest
Jack London believed in Herbert Spencer's theory of "survival of the fittest," which means basically that an organism or group that is better suited to an environment will have a better chance for survival than an animal or group that is less suited. In other words, Spencer suggested that learning did not play a great role in the survival of a species. More often it had to do with luck -- a major environmental change would suddenly make one group of organisms better off than it had been before, and they would therefore live longer and reproduce more.
London clearly makes use of the idea of "survival of the fittest" in The Call of the Wild. By chance, Buck's environment undergoes a tremendous change - he is kidnapped and taken from a "sun-kissed," easy existence to the wilds of the Klondike. Buck survives because he was genetically more suited to that environment than many of the other dogs who were there. He did not need to learn much of anything - the instincts for survival were handed down by his ancestors -- a more poetic version of genetic inheritance.
London takes the idea even more literally than is necessary. If Buck had remained in Santa Clara, he would not have passed on his genetic traits, for there were no suitable mates available to him. At the end of The Call of the Wild it reads that "the years were not many when the Yeehats noted a change in the breed of timber wolves; for some were seen with splashes of brown on head and muzzle, and with a rift of white centered down the chest." Buck has had many children, children who will inherit from Buck all of the experience and "fitness" of their ancestors.
The power of Instinct
This theme also relates to London's interest in Charles Darwin's and Herbert Spenser's work. For the first time there was a scientific theory, which suggested that human beings as well as animals have natural instincts which are merely things passed down through the genetic code. In The Call of the Wild, London dwells a great deal on animal instinct, for Buck's ability to listen to his instinct both makes him more and more powerful and draws him more and more deeply towards the wild. When Buck leads the team into John Thornton's camp, he does not consciously know why he does not get up. He is as capable of continuing as the other dogs, and he has no desire to be killed. Instead, he unconsciously sensed that the snow and ice under his feet were getting weaker and weaker. His instincts told him to go no further, and he obeyed them, saving his life.
One of the unique features of London's novel is that he also writes about human instincts. Men like Francois, Perrault, John Thornton and his partners have shaken off the trappings of civilization, and London implies that this change allows them better access to their instincts. Consequently, they thrive on the trail, making it through multiple dangerous incidents because they trust their impulsive reactions. In contrast, Hal, Mercedes and Charles possess instincts, like all human beings, but they are so suffused with the notions of civilized life that they are unable to access them. London emphasizes the value of instincts, and he certainly presents their reassertion as a positive feature of a more natural, wilder lifestyle.
Loyalty
When Buck is kidnapped and taken to the Klondike, he learns that loyalty is a characteristic which differs under the law of Club and Fang. Though this new kind of loyalty may seem less genuinely good, Buck discovers that it is stronger and perhaps truer than the loyalty he had understood before. When Buck lived in California with Judge Miller, loyalty was a noble idea. He certainly felt loyal to the Judge when he protected his grandchildren or walked steadfastly by his sons. But his loyalty was not only never tested, he also knew that it would never be tested.
In the Klondike, Buck discovers that loyalty is not so noble, because it stems primarily from self interest. His team's and his human leaders' survival depends upon the behavior of each member of the group. They are fiercely loyal to their goal and to helping each other, because it is the only way to survive. When Spitz acts against the best interests of the group by attacking Buck while they are fending off the foreign huskies, he proves that he is disloyal. This is a serious charge, because it could lead to the destruction of the entire group. After that time, Buck finds it easy to turn the other dogs against Spitz, for they know that he cares more about his own selfish desires for leadership than the survival of the group. The groups' loyalty is tested again and again, and each time it proves true. The strength of this loyalty suggests that loyalty based on self-interest is ultimately stronger and more meaningful than loyalty based on a noble ideal.
When Buck falls in with John Thornton, he contradicts this idea to some extent. He loves John Thornton so much that he is willing to do things that are against his self-interest, even stupid things such as jumping off a cliff. But London seems to go to some effort to emphasize that Buck performs these acts out of passionate love, rather than pure loyalty.
Power
In California, Buck believed he was very powerful, for he was the most important dog in Judge Miller's household. He ruled over all of the other dogs, and he even believed that he ruled over the people. In the Klondike, he learns what a hierarchy really is, and he understands that power is truly the power over life and death. All of the dogs either have power, and must exert it in order to survive, or they give up their power to a bigger and stronger dog and can merely hope that that dog will protect them.
Once Spitz fears Buck's power, Buck realizes that he must exert it. The appearance of power must lead to the assertion of power. The only other option is death. Buck quickly learns one of the most important laws of Club and Fang. When Curly is killed for making a friendly advance to another dog, he recognizes that he is in a world where it is kill or be killed. He immediately begins to see the world in terms of who he has power over and who has power over him.
The issue of power exists both in the relations of the dogs among themselves and in the relation of the dogs and the men. Slowly over the course of the novel Buck learns that human beings do not have intrinsic power over dogs. When he asserts his right to leadership of the sled, he imposes his will on Francois, even though Francois has a club. When he kills the Yeehat Indians, he consciously acknowledges that he need never fear human beings again. In this world, he is more powerful than a human being. In light of this view of power, London suggests that a wild, natural existence is not as free as the reader might imagine. Buck is free because he is the most powerful, but he must never for a moment let down his guard. The natural world is dominated by rules and codes just as the civilized world is, and in this world, Buck can read and understand the subtlest of controls.
Companionship
One can reframe Buck's journey in The Call of the Wild as a search for companionship. Buck is never alone in the novel, but instead travels between a various number of humans and other dogs, often wondering why he is not completely happy. At the beginning of the novel, Buck does not seem to lack for anything. One might wonder whether Buck is actually better off at the end of the novel, if he never felt unfulfilled in his Santa Clara home. But, it seems likely that Buck was simply young, and as he grew older he would have felt the lack of true companionship more strongly.
Buck encountered several positive kinds of companionship along his journey. First Francois and Perrault, then the Scotchmen, engaged him in meaningful relationships based on work, along with the rest of the dog team. Though Buck was sometimes tired and uncomfortable, he was fulfilled by his work. His relationship to John Thornton was obviously superior to these, and it was at its peak when he was able to work for John Thornton, fulfilled by his labor and inspired by his love. But, throughout these times, he was restless and knew something was missing.
Buck always dreamed of his companionship with wild man, because only that partnership was completely equal. Then, Man and Dog were united by mutual goals, mutual labor, mutual fears and mutual desires. When Buck meets the lone wolf in the woods and runs with him for a few hours, he finally understand the meaning of the call that he has felt. His relationship with the wolves is like his relationship with wild man. When John Thornton dies, Buck is free to go with the wolves. He mourns John Thornton, because he loved him, but the story suggests that Buck's final home among the pack of wolves is the right one.
The joy of labor
Another idea held by London, which he clearly makes use of in The Call of the Wild is his belief in socialism. London seems to hold a romantic and general idea of socialism rather than a radical and specific one. The most important idea imbued in The Call of the Wild is that everyone is suited to a particular kind of work, and everyone will be happiest if they are doing that work. London lived this ideal, for even when he was making a great deal of money as a writer, he was always trying out new ways of keeping busy and contributing to society, whether he was exploring new ways of farming or advocating for women's suffrage.
In The Call of the Wild, London portrays the dogs as happiest when they are engaged in labor. The more appealing characters, such as Dave and Sol-leks, come alive only once they have been strapped into their traces, ready to take to the trail. Dave's refusal to abandon his position is as noble and heart-wrenching as any human sacrifice, and though it is heartbreaking when he is shot, it also seems like the kindest course of action. When Buck is leading the sled team for John Thornton, he becomes restless and a little unhappy only when Thornton and his partners find gold, and there is little work for the dogs to do. Arguably, Buck dreams of his ancient master, because only then was he invested in a human partnership with completely mutual goals, desires and needs. Their work was the same and it was constant, and there could be no better relationship for a dog. As much as Buck loves John Thornton, he finds his real happiness roaming the woods, killing his own food, constantly engaged in the act of defending or sustaining his life.
London does not make entirely the same point with regard to the humans of the book. Hal, Mercedes and Charles are clearly unsuited to this work and should never have undertaken it. Perrault and Francois live for the trail almost as much as the dogs do. But, John Thornton, probably intended to be the most appealing human character, seeks gold so that he will no longer have to labor. One might suggest that London dislikes John Thornton's quest for gold. As he, his men, and the dogs searched for gold, they were immensely happy. There needs were met, they enjoyed each day, and they were fulfilled by their search. As soon as gold was discovered, they labored merely for the recovery of money, and the work itself was not pleasurable to them. Ultimately, John Thornton's inability to recognize the true value of life in the wild may have lead to his death at the end of the novel. While seeking gold, Thornton lost touch with his instincts and made himself vulnerable to attack.
The Virtue of Humanity
Throughout the novel London questions the idea of humanity as a virtue. He demonstrates clearly that men do not innately possess any virtues, and that in some circumstances, men are the most virtuous who have become the least civilized. He also makes it clear that the virtues assigned to the idea of humanity fit equally well into the world of animals. The idea of humanity as a virtue (the quality of being humane) suggests that civilization has allowed human beings to morally develop further than wild creatures. But, Hal, Mercedes and Charles represent the most "civilized" people in the novel, and they ultimately act selfishly and cruelly. Outside of their natural position, humanity seems a fairly useless virtue.
In contrast, Buck and the other dogs do not generally perform selfless acts or sacrifice their own interests solely for others; however, they also enforce a strict code of putting the survival of the group as a whole above the mere survival of the individual. When Buck meets John Thornton, he does begin to perform selfless acts, because he is inspired by love, but those acts have nothing to do with any notion of humanity.
London suggests that the idea that humanity is a virtue is merely a conceit of human beings. People are no more likely to be genuinely kind or genuinely careful of others than animals are -- they are simply more likely to try to disguise their own selfish desires and actions.
