A study suggests ancient dogs came from Siberia by tagging along with their humans over a land bridge that once connected North Asia and the Americas.

These ancient dogs became the very first dogs in America and could have been the pure-bred American dogs if not for the European colonization that took place afterward. These ancient American dogs lived for about 10,000 years until they were almost wiped out by the European breeds that, on the other hand, tagged along with their European humans as they colonized the continent.

The Pre-contact Dogs

An analysis of the DNA of these ancient dogs revealed that they had unique genetic signatures never found from any other dog breed at present, not even from any other breeds around the world. This breed, referred to in the study as the pre-contact dogs, would have been entirely wiped out if not for a gene that survived not as a dog but a canine tumor that has now spread worldwide.

The present findings aimed to overthrow previous studies suggesting that these pre-contact dogs evolved from the domesticated North American wolves.

The most important take away from the study, however, is the thought that dogs has always been the men's best friend. Their relationship can be traced back from the earliest of times.

"This study demonstrates that the history of humans is mirrored in our domestic animals. People in Europe and the Americas were genetically distinct, and so were their dogs. And European colonists largely replaced indigenous people in the Americas, and amazingly, the same is true of their dogs," said Greger Larson, senior author of the study and the director of the Palaeo-BARN at Oxford.

America's First Dogs

For the study, published in the journal Science on July 6, the researchers analyzed the nuclear DNA of these pre-contact dogs. They compared the genomic signatures from 71 mitochondrial and seven nuclear genomes of ancient North American and Siberian dogs. These samples were from 9,000 years ago. Nuclear DNAs are the ones inherited from both parents while mitochondrial DNAs are the ones being passed down only from mothers to the offspring.

The analysis revealed that the pre-contact dogs had not a single genetic link with modern American dogs, neither do they have any genetic similarity with the Chihuahuas, Labradors, and Xoloitzcuintli which are supposedly the famous American dog breeds.

In fact, these breeds were found to have descended from Eurasian dog ancestry, introduced to the America between the 15th and 20th centuries according to Angela Perri, the co-first author of the study from Durham University. The pre-contact dogs, however, shared genetic similarities with the ancestors of the Siberian Husky.

"By looking at genomic data along with mitochondrial data, we were able to confirm that dogs came to the Americas with humans and that nearly all of that diversity was lost - most likely as a result of European colonization," said Kelsey Witt, an author of the study and the one who led the analysis of the sample DNAs.

The team suspected that epidemics and hunting might contribute to the purge of these pre-contact dogs. They could also be killed purposely by the Europeans like what they did with the indigenous people. They also believed that the Europeans might have killed the pre-contact dogs because they prefer the breed that they brought from their homelands.

Cancer Tumor

The team also discovered a link between the pre-contact dogs and the canine transmissible venereal tumor or CTVT. The team saw that the sexually transmitted disease among dogs had a similar genetic structure — probably due to mutations — with the dog that was closely related to the pre-contact dogs. This suggested that CTVTs originated some 8,000 years ago.

The next step for the team is to reconstruct how the pre-contact dogs may have looked and how they behaved.

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