Answer:
here are probably several messages in London's book - and from a subjective view you should perhaps be selective. Critically, the story plots the course of domestication (in comfortable and loving surroundings) to work (as a sled dog) to feral and ultimately a 'return to the wild'. Throughout the story Buck is faced with a variety of personalities and his transition from pampered pet to 'working dog' is marked by brutality - and yet through that transformation Buck becomes 'more alive'; hardening both his physical and psychological state. His ultimate supremacy over Spitz to become the lead dog marked a 'turning point' when Buck had completely 'converted' and had no vestiges of the 'pet' he was originally in the story. His association and ultimate affection with Thornton - as a protector, also demonstrated a change, he did not regress to his earlier domesticity and continued received the 'call of the wild'.