By Ellen Gibson of Reuters:

Dog genes that code for such signature pet traits as the furrowed skin of the Shar-Pei have been identified in a study that shows how centuries of breeding gave rise to 400 kinds of domestic dogs.

Researchers analyzed the genes of 275 dogs in 10 breeds to see how breeding practices have altered their DNA, the hereditary template in their cells. The results, reported last week in the Proceedings of the National Academy of Sciences, show that some conspicuous physical traits, or phenotypes, such as height and coat color, can be traced to particular genes of beagles, border collies, dachshunds and poodles, among other breeds.

"When you have a Chihuahua that's nine inches tall and a Great Dane that is seven feet tall, that can be traced back to IGF1," the gene that influences dog size, said Joshua Akey, a geneticist at the University of Washington in Seattle who was the paper's lead author.

Understanding how breeding leads to artificial selection of some doggy DNA can clarify the way genes give rise to appearance and behavior in other species, the researchers said. Such knowledge "holds considerable promise for providing unique insights into the genetic basis of heritable variation in humans," they wrote.

Dogs are "a great system for understanding how genetic variation influences how individuals in a population act differently, look different and have different susceptibilities to disease," Akey said in a telephone interview.

Domesticated dogs have been bred for more than 14,000 years, the report said. The strict form of selective breeding used today to turn out desired characteristics in the animals is a more recent phenomenon.

"Most dog breeds were formed in the last 500 to 1,000 years, a relatively short time frame in terms of evolution," Akey said.

Today there are more than 400 genetically distinct breeds of domestic dog, yet "relatively little progress has been made on systematically identifying which regions of the canine genome have been influenced by selective breeding during the natural history of the dog," the study said.

Dog genome research progress has been fairly slow, partly for economic reasons, but partly, I suspect, because dogs aren't really that variable, strange as it may seem. Without breeding, dogs in the tropics seem to wind up medium size, short-haired, and yellowish, reddish, or brownish.

My hunch is that genetic diversity in dogs will prove to be narrow but deep, focusing on a small number of genes that vary sharply, whereas genetic diversity among humans will prove broader but shallower than among dogs, involving more genes than among dog breeds, but not as sharply defined.