The Chihuahua breed represents one of the most ancient and cherished of all dog breeds. Depending on the actualahuahua, the breed may have originated as far back as the 3rd century B.C. However, most agree that the evolution of the Chihuahua can be traced back to Mexico in the 5th century. What is known about the origin of the dog is that it is believed to be the result of crossing either a Chinese dog with a imported Tibetan Mastiff by either the Toltecs, a Xihuahua, a Mexican Hairless or a Mexican hairless dog. However, the true question of how this breed originated may never be known.