On the Trail of the Cat, Scientists Find Surprises

"If it came from Iran, you would think it would look like cats from Turkey and Israel," she said. Instead, the Persian "looked more like a Western European cat."

When the researchers examined the genes of what are thought to be distinct breeds, they were unable to find significant differences among many of them.

"An example would be Persian and exotic shorthairs. When you look at those two breeds, you can't distinguish them from one another" by their genes, she said.

The same was true for the Burmese and the Singapura, as well as the Siamese and the Havana brown. While Havana browns are considered a separate breed in the United States, European cat breed associations consider them a color variation of Siamese.

"Some people will say, 'Ha, ha. I told you so.' Some other people will be disappointed," Lyons said.

Breeds look very different because of variations in a single gene, which is not enough to distinguish them genetically, she said.

The researchers also found interesting relationships that track human history. Italian and Tunisian cats, for example, are a mix of Western European and Mediterranean cats, probably reflecting the close historical ties between Tunisia and western Europe. Cats from Sri Lanka and Singapore are a genetic melange of cats from Southeast Asia, Europe and elsewhere, which could be a "relic of British colonialism," the researchers wrote. The same goes for the Abyssinian.

The finding that cat lovers should be concerned about is that some breeds have become so inbred that the amount of genetic variation among them is getting dangerously low. That tends to lead to higher levels of illness, Lyons said.

"That could have consequences for the cats' health. The more genetic variation, generally the healthier the population will be. So some cat breeders need to be careful that there's not too much inbreeding going on," she said.

The Burmese and Singapura breeds had the least diversity, she said, while Siberians had the greatest, along with Norwegian forest cats, Maine coons and Japanese bobtails.

About half the breeds examined had genetic variation comparable to randomly bred cats, which is good, but the other half had less.

"You don't want to say they are in trouble, but it's something we should note," Lyons said.

The findings could help guide breeders, Lyons and others said.

"This is new and very useful information," said Susan Little, president of the Winn Feline Foundation, a nonprofit group that partially funded the work. "It helps improve the ability of breeders to reduce the prevalence of disease by developing a healthy breeding program. It's extremely important."

Despite the shrinking genetic diversity, purebred cats remain far more genetically diverse than purebred dogs, noted Marilyn Menotti-Raymond, who studies cat genetics at the National Cancer Institute. That's because people have been breeding cats for about 200 years at most, and there is more interbreeding than among purebred dogs, she said.

"Everyone is aware of the problems that can occur from the small gene pool in some dog breeds," said Menotti-Raymond, who, in the same issue of the journal Genomics, reported similar findings in a different sample of 611 cats representing 38 breeds. "I was actually surprised at the level of genetic diversity in cats, and that's good."