The early Mastiff was called a molosser or molossus. Genetics and breeding dogs to get certain characteristics was unknown then. In 350 BC, Aristotle wrote that the ancestor of the Mastiff was the Molosser. These were the war dogs and guard dogs kept by the Molossoi people, an ancient Greek tribe. Today the two names are often used to mean the same group or family of dogs. For example, the modern St. Bernard is sometimes described as a mastiff and sometimes as a molosser type.