Jack London's The Call of the Wild is a novella taking place during the Klondike Gold Rush in the Yukon a place where strong sled dogs were in high demand. After Buck, a domesticated dog, is snatched from a ranch in California, he is sold into a brutal life as a sled dog. The Call of the Wild details Buck's struggle to adjust and survive the cruel treatment he receives from humans, other dogs, and nature. He eventually sheds the veneer of civilization altogether and relies on primordial instincts and the lessons he has learned to become a respected and feared leader in the wild. The Call of the Wild is London's most popular work and is considered the masterpiece of his "early period." It is often classified as children's literature because of its animal protagonist, but the subject matter makes it valuable for older audiences as well dealing with such subjects as survival of the fittest, civilization versus nature, and fate versus free will