The first dogs of America have been eliminated by Europeans, but their genetic inheritance continues to be a sexually transmitted cancer

The evolutionary journey of how dogs came to occupy millions of living rooms is complicated, full of detours and false starts. A new study published this week in Science seems to shed more light on one of these detours.

He suggests that the first domestic dogs arrived in America were brought by humans from Asia, and then destroyed when Europeans began to make their way to the New World from the 15th century on a regular basis. .

Dozens of researchers collaborated for the expansive study.

They analyzed mitochondrial DNA (the small but unique DNA fragment transmitted only by mothers) of 71 ancient dogs found on archaeological sites in North America and Siberia, the most north of Asia. continents.

They also sequenced the nuclear genome (which accounts for 99% of the total DNA) of seven of the old dogs.

Finally, they compared the genomes of these dogs to a variety of modern breeds and other living canine species, such as North American wolves.

These dogs all lived before the Europeans came into contact with the native peoples of the Americas. But even the oldest specimens – dating back about 9000 years – lived a long time after humans had crossed the Bering Strait to settle throughout North and South America.

So, it's a mystery as to where and how these domesticated dogs evolved.

Confirming previous work, the researchers found that these old American dogs have very little in common with modern dogs today, genetically speaking. And they also do not have any common links with the North American wolf, suggesting that they were not tamed by the local dog population encountered by proto-Americans.

But these dogs shared more genetic similarities with breeds such as the Siberian Husky, but not as direct descendants. Instead, these dogs shared an ancestor with the husky.

The most likely scenario then, say the researchers, is that pre-European contact dogs had migrated to the Americas from Siberia with a group of humans about 10,000 years ago. But although this lineage has flourished for centuries, it seems that their destiny was inextricably linked to the indigenous peoples who were killed by the Europeans.

"After the arrival of Europeans, native American dogs have almost completely disappeared, leaving a minimal genetic inheritance in"

Although some American dogs may have been annihilated by epidemics or deliberately killed by Europeans, as were often the natives, there are probably other reasons for their disappearance. The Europeans would have simply preferred to only raise and support the dogs that they brought back from their home country.

Meanwhile, Siberian huskies and other Arctic dogs probably descended from the ancestors of pre-contact dogs, but have a lot of DNA mixed with European and Asian breeds.

The results seem to undermine the popular narrative that breeds as chihuahuas descend from older American dogs, as their mitochondrial DNA was less than two percent in common with the older dogs in this study. However, not all experts are convinced that this is the case,

"The picture is not as clear as they want," said Peter Savolainen, associate professor of genetics evolutionist at the Royal Institute of Technology Stockholm . ] Gizmodo . "They used what they say is a global data set [of dogs’ DNA] but it's not really."

Savolainen, who is not affiliated with the present study, notes that his research and that of others have shown that some breeds, such as Carolina It seems that dogs lack many genetic markers found in dogs of European descent.

Dog DNA from other ancient sites of the Americas not included in the study was also found to have more similarities with the Chihuahua and other South American breeds that this study did.

Because of this, Savolainen does not neglect the possibility that, although these pre-contact dogs may not have direct descendants, previous migrations could have resulted in dogs whose genetic inheritance survived to the point of death. 39 to the present day

. is the theory of researchers on the Canine Transmissible Venereal Tumor (CTVT), a form of sexually transmitted cancer that has spread worldwide.

Because CTVTs (and all cancers) are essentially the mutated form of an animal's DNA, it is possible to trace its genetic structure to the dog that developed it first. . The researchers found that this "founding CTVT" dog was closely related to pre-contact dogs, suggesting that the disease appeared 8000 years ago

"It's pretty amazing to think that the only survivor of 39, a lost line is a tumor. In a statement, the main author, Mayor Ní Leathlobhair, a researcher at the Department of Veterinary Medicine at the University of Cambridge, said in a statement that the disease can spread between dogs.

According to Krishna Veeramah, geneticist at the University of Stony Brook, who studied the evolution of the ancient dog, the genetic history of humanity's best friend brings new clues. "I think it is an important technical feat to obtain more" Veeramah, who is not affiliated with the research, told Gizmodo . He noted that we had only sequenced nuclear DNA from three other old dogs up to now.

"Although the study does not really address the ultimate origins of wolf dogs (this will require older samples from Eurasia), it sheds new light on an important aspect of # 39; dog-human history. "

[Science]