Adventure, Coming of Age
With the Yukon Gold Rush as a back-drop, London is free to tell us a thrilling tale of action and adventure: complete with cute puppies, dead bunnies and a whole heck of a lot of fighting. There's no better place to do it than the Yukon, and a coming-of-age story—in which a tender young soul goes out into the world to learn how scary life can be—makes a great foundation for all the fighting and struggling.
All of that's pretty typical for literature: plenty of books do the same thing. But London did it with a wolf… a very cool choice that also helps his historical adventure distinguish itself from the pack of coming-of-age tale starring human males. How boring.