I always knew this. I first read that chihuahuas actually came from China back before I got my first chihuahua. The original chihuahua, the dog from Mexico and named for the capital city, originally weighed about 50 pounds. The Aztec royalty used them as heat pads on cool nights. Hence the term for a cold night a "3-dog night". The cooler it got, the more dogs were piled on to a person to keep warm. And chihuahuas really do seem to keep you warmer than any other dog. They also guarded their masters viciously. That's why the modern chihuahua has a plucky, terrier-like temperament. The only thing that has changed is the size. That changed when the Chinese invaded Mexico and took these canine heat-pads to their land, and their emperor. The dogs were fed a diet of rice and pork, which stunted their growth and over time the size stuck. Today, you may still see some throwbacks to the original breed, but none are 50 pounds anymore. The largest purebreed chihuahua I've ever seen was a whopping 25 pounds. It was tall, and fat. Today, with mock registries taking over and mediocre breeders continuing to breed dogs like that, I'd question if that dog really was a purebreed chihuahua. But that one did have AKC registration. I saw the pedigree and all. It was just a mediocre specimen.
Any time you see someone using ACA (American Canine Association) or CKC (Continental Kennel Club--not to be confused with the more reputable Canadian Kennel Club) or APRI (American Pet Registry, Inc--also known simply as APR) you simply must question the dog's ancestry. People who use these registries typically cross breeds, or have no accurate records of their breedings. Then there's the registries themselves. Look at their site, they register designer mongrels. Bad idea for any registry's reputation! Anyway, here's the article I found. I thought it was interesting.
Small Dogs Originated in the Middle East
These miniature mutts were the descendants of gray wolves, which also happen to be smaller than many other wolves.
Small dogs the world over can all trace their ancestry back to the Middle East, where the first diminutive canines emerged more than 12,000 years ago.
A new study, which appears in BMC Biology, focused on a single gene responsible for size in dogs. Researchers found that the version of the gene IGF1 that is a major determinant of small size in dogs probably originated as a result of domestication of the Middle Eastern gray wolf, which also happens to be smaller than many other wolves.
In terms of which came first, big dogs or small dogs, the answer is now the former.
"Archaeological studies suggest that ancient (dog) remains found in Belgium, Germany and Western Russia, which date to 13,000-31,000 years ago, were most similar in body size to the Great Dane, while those from the Middle East dating to about 12,000 years ago were most similar to a small terrier," lead author Melissa Gray told Discovery News.
For the study, Gray, a researcher in the Laboratory of Genetics at the University of Wisconsin, Madison, and her colleagues traced the evolutionary history of the IGF1 gene. To do so, they surveyed a large sample of gray wolf populations, other wild members of the Canidae family, and numerous breeds of dogs.
Gray and her team first confirmed that all domesticated dogs trace their heritage back to gray wolves. She indicated the jury is still out as to when and where the world's first dog -- of any size -- emerged.
All small dogs, normally weighing 20 pounds or less, share the variant of IGF1 also found in Middle Eastern gray wolves, the scientists discovered. This means the gene must have surfaced early in the history of small dogs, but after dogs in general were first domesticated.
The DNA studies, combined with the archaeological record, then suggest that at least 12,000 years ago, the first domesticated small dogs entered the world, with humans playing a major role in the process.
"(There) could have been a mutation arising early in the history of dogs," said Gray, "which was maintained by breeding and artificial selection by humans, or could have been an adaptive trait that developed during domestication as a means to coexist with humans."
The timing and location provide intriguing clues, as Middle Eastern societies then were moving away from the hunter-gatherer lifestyle and towards agriculture-based communities.
"Small (dog) size could have been more desirable in more densely packed agrarian societies where dogs may have lived partly indoors or in confined outdoor spaces," Gray explained.
"It is unlikely that dogs at that time were used as a source of protection, but more likely that they were used initially for their fur, as a food source, and possibly companionship," she added.
Reduction in body size is a common feature of domestication and has been observed in other animals, such as cattle, pigs and goats.
David Macdonald of the University of Oxford and Carlos Driscoll of the National Institutes of Health point out in a separate paper in the Journal of Biology that most of the Western barnyard animals were domesticated beginning at around the same time 12,000 years ago.
Dogs stood out from the rest, however, because they were "in the role of not just a treasured companion, but a precursor to wealth and inequality" since "dogs are likely to have become status symbols as well as being intrinsically valuable," Macdonald and Driscoll wrote.