I would say Brian matures through his new ability to have patience throughout the novel. The setbacks that would have immobilized the old Brian now he can manage it. He also learns how he can control his temper because he realizes how frustration and hopelessness doesn’t make it any better It just makes the situation worse.
Brian had lost a lot of his body weight since the crash, and he remains thin for years. Many of the changes Brian underwent in the wilderness seem permanent, such as his observant and thoughtful nature, and food never loses its wonder for him.
