In The Call of the Wild why is the first chapter called "Into the Primitive?"

When the book begins, the reader is introduced to Buck.
 He has a wonderful life with a very loving family.  He is well taken care of, and his
life in general is quite "cushy."  Some readers might even claim that Buck's life before
he was dog-napped was a pampered life.  

readability="21">

But Buck was neither house-dog nor kennel-dog.
The whole realm was his. He plunged into the swimming tank or went hunting with the
Judge’s sons; he escorted Mollie and Alice, the Judge’s daughters, on long twilight or
early morning rambles; on wintry nights he lay at the Judge’s feet before the roaring
library fire; he carried the Judge’s grandsons on his back, or rolled them in the grass,
and guarded their footsteps through wild adventures down to the fountain in the stable
yard, and even beyond, where the paddocks were, and the berry patches. Among the
terriers he stalked imperiously, and Toots and Ysabel he utterly ignored, for he was
king,—king over all creeping, crawling, flying things of Judge Miller’s place, humans
included.

That paragraph
makes it clear that Buck wasn't a lazy pampered dog though.  On the contrary, he was
quite active on his California estate.  In addition to being active, the paragraph makes
it clear that Buck's owners loved him, and they treated him like a member of the family.
 Buck, in turn, treated them like they were his family, because
Buck truly believed that he was the ruler over
everything.   

All that changes for Buck, when he is taken
from the estate, sold, and brought to the Alaskan wilderness.  The area that Buck is now
living in is much more primitive in general.  There is simply less civilization, so the
title makes sense in that regard. 

But I think the main
reason that the chapter is called "Into the Primitive" is because of Buck's experience
with the man in the red sweater.  Buck is firmly beaten and humiliated by the man, but
learned a valuable lesson.  He learned that might makes right in this strange new area.
 That rule becomes a law to Buck.  He calls it the "primitive law," and throughout the
book Buck learns how that rule affects him, other dogs, and his owners.
 

He was
beaten (he knew that); but he was not broken. He saw, once for all, that he stood no
chance against a man with a club. He had learned the lesson, and in all his after life
he never forgot it. That club was a revelation. It was his introduction to the reign of
primitive law, and he met the introduction
halfway.