Once Buck learns the hard lesson of the man in the red sweater, he adapts by watching the other dogs and understands what the laws of the wild mean. Then, his instincts begin to emerge, and this speeds up his total immersion into the life as a sled dog. He had been a picky eater before, but he soon learned to eat as fast as he could before the others took it away from him. He even learned to steal, and
this first theft marked Buck as fit to survive in the hostile Northland environment. It marked his adaptability, his capacity to adjust himself to changing conditions, the lack of which would have meant swift and terrible death. It marked, further, the decay or going to pieces of his moral nature, a vain thing and a handicap in the ruthless struggle for existence....but in the Northland, under the law of club and fang, whoso took such things into account was a fool, and in so far as he observed them he would fail to prosper.
Totally regressed into an uncivilized animal, Buck would now steal or run from a fight if it meant saving his life. He physically adapted very quickly after his mental adjustment. His body became tough and hard, and his life as a tamed dog disappeared.