Buck was returning to his ancient instinctual roots is the answer.
Explanation:
the Call of the Wild is a book written by Jack London, an American writer and journalist. The question refers to the main character, Buck, which was a dog taken to Alaska after he is stolen from his home in California. The speaker considers Buck's progress as a retrogression because he was coming back to his feral instincts in order to survive in such hard conditions as a sled dog.
<span>This quote describes Buck, who is a dog and the main character in Jack London's The Call of the Wild. ... Throughout the story, Jack London puts an emphasis onBuck's retrogression from a sated and aristocratic dog, into a wild and vicious creature of the primitive world.</span>
