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People in North America trace their ancestry back to places all over the world - Asia, Africa, Europe. Many of our canine friends do, too. A new study finds that at least some dogs have been here a very long time.

As NPR's Rhitu Chatterjee reports, some modern breeds may have descended from animals that accompanied the very first groups of people who migrated from Asia to America.

(SOUNDBITE OF A BARKING DOG)

RHITU CHATTERJEE, BYLINE: A quick visit to a dog park can tell you a lot about American dogs. When I visit Lincoln Park in Washington, D.C., there are a range of breeds running around.

UNIDENTIFIED WOMAN #1: Teddy, (unintelligible).

CHATTERJEE: There are the popular purebreds, like this beautiful white labrador retriever.

UNIDENTIFIED WOMAN #1: Come here, buddy.

CHATTERJEE: And then there are mixed breeds, like Lola.

UNIDENTIFIED WOMAN #1: She is a Schnoodle, a schnauzer-poodle mix.

CHATTERJEE: But these dog breeds are relatively recent arrivals. Peter Savolainen is an evolutionary geneticist at the KTH-Royal Institute of Technology in Sweden. He says there've been dogs in America for far longer.

PETER SAVOLAINEN: There is both archaeological and historical evidence that the native peoples of America had dogs.

CHATTERJEE: He's the lead author of the new study published this week in the British journal Proceedings of the Royal Society B. No one really knows what happened to these ancient dogs. Some must have interbred with all the European dogs that came later. Savolainen wanted to know if any of the ancient dog genes could still be found in modern American dogs. To find out, he and his team decided to look at mitochondrial DNA. Now, that's the DNA inherited only through the mother and changes very little across generations.

SAVOLAINEN: And this means that you can go back in time as far as tens of thousands of years.

CHATTERJEE: They analyzed samples from several of the most traditional types of dogs in North and South America.

SAVOLAINEN: Inuit sled dogs, Greenland dog, Alaskan Malamute, Chihuahua, Mexican hairless dogs, and Peruvian hairless dogs.

CHATTERJEE: All these dogs are associated with cultures that go back way beyond the arrival of Europeans. And when they compared their DNA with that of dogs in Europe, they were very surprised.

SAVOLAINEN: These breeds are indeed almost pure indigenous breeds. They have very little influence of European dogs.

CHATTERJEE: Then they compared the modern dog DNA with that of ancient dogs found in archaeological sites in Alaska and South America. And in the case of the Chihuahua, they found a close match.

SAVOLAINEN: So, we have exactly the same unique DNA type in Mexico 1,000 years ago and in modern Mexican Chihuahua.

CHATTERJEE: They also found that most of these indigenous dogs had a strong genetic resemblance to present day East Asian dogs. Now, he admits that the picture may get more complicated if one looks at the paternal side of inheritance. But he says his findings do show a direct connection between some modern American breeds and the very first dogs that migrated to the Americas from Asia. Adam Boyko of Cornell University College of Veterinary Medicine agrees.

ADAM BOYKO: Gives us sort of the clearest picture to date as to, you know, whether or not we see any contribution of pre-Columbian Native American dogs in today's dogs.

CHATTERJEE: He says it also shows why scientists should look beyond recognized breeds for signs of ancient DNA. The team also looked at the DNA of feral dogs.

BOYKO: There is a significant component of genetic diversity retained in these semi-feral street dog populations, as well as indigenous breed populations.

CHATTERJEE: And studying that genetic diversity, he says, may tell us more about the history of dogs in America. Rhitu Chatterjee, NPR News.

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