What is the moral of The Call of the Wild by Jack London?

The Moral to this story is Survival of the fittest.  If you cannot survive, people, or dogs for that matter, will simply forget you. civilization vs. primitive nature is also another aspect of this story that is significant here.  when buck was back at Judge Miller's place, he was civilized and now that he is in the Klondike, it is a dog eat dog world out there. let the best dog win, or strongest, for that matter.