The Chihuahua’s history is puzzling and there are many theories surrounding the origin of the breed. Both folklore and archeological finds show that the breed originated in Mexico. The most common and most likely theory is that Chihuahuas are descended from the Techichi, a companion dog favored by the Toltec civilization in Mexico. No records of the Techichi are available prior to the 9th century, although dog pots from Colima, Mexico, buried as part of the western Mexico shaft tomb tradition which date back to 300 B.C. are thought to depict Techichis. It is probable that earlier ancestors were present prior to the Mayans as dogs approximating the Chihuahua are found in materials from the Great Pyramid of Cholula, predating 1530 and in the ruins of Chichen Itza on the Yucatán Peninsula.
Chihuahuas are very small dogs, and are the smallest breed recognized by some kennel clubs. There are two main varieties recognized by kennel clubs, the short-haired and the long-haired. There is a second varietal split as well, having to do with the shape and size of the dog’s head. These two descriptive classifications are “apple head” and “deer head”, but only the apple head is conformationally correct.
Breed standards for this dog do not generally specify a height; only a weight and a description of their overall proportions. As a result, height varies more than within many other breeds. Generally, the height ranges between 6 and 9 inches (15 and 23 cm); however, some dogs grow as tall as 12 to 15 inches (30 to 38 cm).Both British and American breed standards state that a Chihuahua must not weigh more than six pounds for conformation. However, the British standard also states that a weight of two to four pounds is preferred and that if two dogs are equally good in type, the more diminutive one is preferred. The Fédération Cynologique Internationale (FCI) standard calls for dogs ideally between 1.5 and 3.0 kg (3.3 and 6.6 lbs.), although smaller ones are acceptable in the show ring. Pet-quality Chihuahuas (that is, those bred or purchased as companions rather than show dogs) often range above these weights, even above ten pounds if they have large bone structures or are allowed to become overweight. This does not mean that they are not purebred Chihuahuas; they do not meet the requirements to enter a conformation show. Oversized Chihuahuas are seen in some of the best, and worst, bloodlines. Typically, the breed standard for both the long and short coat chihuahua will be identical except for the description of the coat. Chihuahuas have large, round eyes and large, erect ears, set in a high, dramatically rounded skull.