Genetic analysis reveals origins of dog breeds

In the pages of human history, the paw prints of man's best friend are tracked all over.

As companions, guardians, hunters and herders, dogs come in all shapes and sizes, evidenced by the enormous variety of breeds. New research from the U.S. National Institutes of Health draws a family tree of over one hundred breeds.

The results, published in the journal Cell Reports, have drawn a lineage of 161 dog breeds, forming the largest ancestral tree of Canis familiaris yet.

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First, researchers aimed to understand how the numerous and diverse dog breeds relate to each other. By untangling their complex genome, it would shed light on how those breeds came to be.

Elaine Ostrander, chief investigator of the cancer genetics and comparative genomics branch in the National Human Genome Research Institute and co-author of the paper, said in an interview with CBC News they acquired the DNA samples by going "anywhere the dog people are."

The team of researchers attended agility, herding, and pedigree competitions, as well as Frisbee shows and exclusive breeding clubs to try and fetch dog owners into a study that examined 1,346 dogs around the world.

"It was a general collaboration with the public," said Ostrander. "If we wanted 10 samples of sheepdogs, we got 100. People were really happy to be involved."

With the blood samples acquired, the research team could build a timeline of when and how those 161 dog breeds emerged.

"I've always wondered where German shepherds originated," said Ostrander. "This research gives us information about how they were formed."

The paper uses the golden retriever as an example, using genetic information to show the breed split from the flat-coated retriever in 1895. Written records from that time mention crosses between various breeds from 1868 to 1890 that would result in the golden retriever, which coincides closely with the data from the research.

Breeding for work and looks

The traits that humans desired from their pooches played a significant role in breeding.

Herding and hunting were common desirable qualities, which influenced the breeding of the golden retriever, German shepherd and border collie.

The research indicated was that these desirable traits developed independently across the world in four different places.

"What you want to move bison across a plain is different from wanting a dog to move goats up a mountain," said Ostrander.

Finding the 1st American dogs

Genetic analysis also showed for the first time traces of the "New World Dog", a sub-species that accompanied humans as they crossed the Bering land bridge that connected Siberia to Alaska.

In Central and South America, researchers found unexpected genetic signatures for herding in the native dogs of the region, like the hard to pronounce Xoloitzcuintlels, and the Peruvian hairless dog. The prevailing belief had been that the DNA of the aboriginal American dogs was heavily diluted to the point of extinction.

But an unexpected result of the DNA analysis suggested the two species are a mix of pre-Columbian American and Southern European herding dogs, which explains the herding traits in the South American breeds which normally lack such tendencies.

While archaeological proof existed of the New World Dog, the genetic research in the paper is the first living evidence that they live on through the dogs of today.

Dayna Dreger, a Canadian co-author of the paper, said previous research "suggested the DNA signature of New World dogs. This is the first time we looked at nuclear DNA, which gave us the results."

"We don't have the whole story, but the genetics are there," said Ostrander. We just need to figure out where and when did this happened."

Follow the 'yellow brick road'

Beyond the importance of understanding the origins of dogs in greater detail, this research carries applications for the health of both humans and our furry friends. Ostrander likens it to a "yellow brick road to see how diseases and mutations have travelled."

She said she's been interested in finding "disease detectability genes'for the past 25 years.

The dog research could help with that, since humans share some diseases with dogs, including diabetes, epilepsy and cancer.

"Those genes have been hard to find in humans, but by looking at the 161 dog breeds with their own unique one or two disease genes, we can look at their genome and found out how they were created, and track the migration of diseases," said Ostrander.