While dogs have been man’s best friend for more than 10,000 years, a study of their remains found that early dogs likely arrived from Siberia and left a cancerous tumour that is still found in their canine descendants.
The oldest known domestic dog remains in the Americas are approximately 9,900-year-old skeletons in Illinois.
The findings, detailed in Science magazine, showed that American dogs were not derived from North American wolves and were present before the arrival of European colonists.
Instead, the dogs form a monophyletic lineage that likely originated in Siberia and dispersed into the Americas alongside people.
“When we compare our ancient dog DNA to all other known dog or wolf DNA, we find that the closest relatives are the Siberian dogs. This mirrors what we know about humans at the time and sites in Siberia have records of people using dogs then,” said Anna Linderholm, Assistant Professor at Texas A&M University in the US.
The team sequenced 71 mitochondrial and seven nuclear genomes from ancient North American and Siberian dogs from time frames spanning 9,000 years.
After the arrival of Europeans, native American dogs almost completely disappeared, leaving a minimal genetic legacy in modern dog populations.
The closest detectable extant lineage to pre-contact American dogs is the canine transmissible venereal tumour, a contagious cancer clone derived from an individual dog that lived up to 8,000 years ago.
This cancer that spread through the mating of dogs thousands of years ago is still present today and is the last remaining trace of these early dog populations that arrived in the Americas, the study showed.
“It is amazing to think that these cancerous cells spread and that they still exist all over the world. So in a weird way, the ancient dogs of America live on through these cancerous cells,” Linderholm said.
