The Tibetan mastiff is a large dog that originated in the mountains of Central Asia alongside the nomadic tribes who carved out a life there. They were traditionally used to protect homes, farms and flocks and could fight or scare off larger predators like leopards. In 2004, Chinese researchers found that the genetic line of the Tibetan mastiff had peeled away from the wolf 16,000 years before most common dog breeds. In 2011, an 11-month-old red Tibetan mastiff sold for $1.5 million, making it the single most expensive dog in the world.