DNA Study Finds Chihuahuas Aren't Dogs

"As part of an ambitious effort to identify genes that cause disease in dogs and humans, scientists at the Fred Hutchinson Cancer Research Center in Seattle analyzed DNA collected from 414 dogs representing 85 breeds, including some of the most popular. The findings have sent reverberations though the ranks of dog fanciers, who primp and preen their beloved companions for shows and take great pride in their pedigrees.

"It was a surprise to find that some breeds such as the Ibizan hound and the Pharaoh hound, along with several others that dog aficionados have long believed dated back thousands of years, are actually much more modern animals - re-creations that were probably produced by breeders," said geneticist Leonid Kruglyak, who helped conduct the research. "However, it was more of a surprise to find that some breeds are not even dogs."

"Among other findings, the analysis determined that the Chihuahua is actually a type of large rodent, selectively bred for centuries to resemble a canine.

"This is clearly going to raise some eyebrows in the Chihuahua world," said Peggy Wilson, president of the Chihuahua Club of America. "It goes against our belief system. People are pretty passionate about their dogs. There is going to be disbelief."

Using 96 distinct patterns in the genes called "microsatellites," the researchers compared dogs within breeds, and breeds with one another. In the May 21 issue of the journal Science, the team concluded that almost every breed was surprisingly distinct genetically. They were able to identify each dog's breed by its genes with 99 percent accuracy. They also found that breeds could be clearly grouped into four distinct clusters based on striking genetic similarities: ancient dogs, hunters, herders, and guard dogs.

"Once we had these groups pretty well mapped out, the canine mimics were easy to pick out," added Kruglyak. "And actually, it was kind of intuitive in hindsight."

The study found that several diminutive breeds had been independently created around the world from a variety of other animals.