The first American dogs were eliminated by Europeans, but their genetic inheritance continues as a sexually transmitted cancer

The evolutionary journey of how dogs came to occupy millions of living rooms is complicated filled with detours and false starts. A new study published Thursday in Science seems to shed more light on one of these detours. He suggests that the first domesticated dogs to come to America were brought by humans from Asia, to be subsequently eliminated when Europeans began to make their way regularly to the New World from the 15th century.

Dozens of researchers collaborated in the expansive study. They analyzed mitochondrial DNA (the small but unique DNA fragment transmitted only by mothers) of 71 ancient dogs found at archaeological sites in North America and Siberia, the northernmost region of the world. l & # 39; Asia. 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 earliest specimens – dating from about 9,000 years ago – were still living long after humans first crossed the Bering Strait and settled throughout America. North and South. So, it's a mystery as to where and how these first 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 legacy in the" 19659004 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.Europeans would have simply preferred to only raise and support the dogs that they brought back from their country of origin. During this time, 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. [19659004] The results seem to undermine the popular narrative that chihuahuas descend from ancient American dogs, since their mitochondrial DNA was less than 2 percent in common with older dogs. ens in this study. "The picture is not as clear as they want it," Peter Savolainen, an associate professor of evolutionary genetics at the Royal Institute of Technology in Gizmodo, told Gizmodo. Stockholm. "They used what they say is a global data set [of dogs’ DNA] but it's not really."

Savolainen, who is not affiliated with this study, notes that his research and those of others have shown that some breeds, such as Carolina It seems that dogs lack many genetic markers found in the dogs of European descent. The dog DNA from other ancient sites of the Americas that are not included in the study was also found to have more similarities with the Chihuahua and other South American breeds that this study did. For this reason, Savolainen does not neglect the possibility that, although these pre-contact dogs may not have direct live descendants, previous migrations might have brought dogs whose genetic heritage has survived in modern times.

The Canine Communicable Venereal Tumor (CTVT) theory, a form of sexually transmitted cancer that has spread around the world. 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 first developed it. And the researchers found that this "founding CTVT" dog was closely related to the pre-contact dogs, suggesting that the disease had appeared some 8,000 years ago.

"It is pretty incredible to think that the only survivor of a line of lost dogs is In a statement, the main author, Mayor Ní Leathlobhair, a researcher at the Department of Veterinary Medicine of the United States. University of Cambridge, said in a statement that the tumor could spread between dogs.

According to Krishna Veeramah, a geneticist at the University of Stony Brook, who studied the evolution of ancient dogs, l & rsquo; Study has helped to better understand the genetic history of the best friend of humanity

. "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 casts a new light on an important aspect of the world. dog-human story. "

[Science]