The history of domesticated dogs in Canada is not as fluffy and cuddly as you might expect, according to a study published today in Science that explores the origins of our favourite furry friends.

The earliest traces of domesticated dogs in North America are from about 5,000 years after humans first arrived about 15,000 years ago. But very few traces of the domesticated dog native to North America exists. It's as if the indigenous dog population was wiped out in recent history and replaced by European breeds.

According to Maire Ni Leathlobhair, one of the study's authors from Cambridge University, the eradication was likely due to a combination of factors.

"Disease introduced by Europeans could be quite an important one of those," she said. "The other could be persecution of native dogs by European colonists—it could be a way of targeting Indigenous people. It could also be that European dogs were just favoured for whatever reason. Maybe they were better trained, or something like that. It's difficult to say."

The lineage of North American dogs

Originally, American dogs didn't come from the domestication of American wolves, but from the domesticated dogs that came over with the First Peoples from Siberia and existed here for about 5,000 years until the settlers arrived with their dogs in the 15th century.

Once the domesticated Siberian dogs arrived in North America, they co-existed with the First Peoples for almost 9,000 years before Europeans arrived. The ethnographic records and hard evidence suggests they were the constant companion of the Indigenous populations of North America, and yet, very little trace of them exists today in the genomes of modern dogs.

The Siberian huskies, malamutes and general sledding dogs are considered to be the closest to the original North American breeds. They likely came over in a wave of migration only about  1,000 years ago—roughly 500 years before the Europeans arrived—meaning that they are a little more closely related. Still, it does look like they are mostly European in origin.

Using tumour cells to track canine history

Ethnographic records show that there were domesticated dogs involved in sledding in the north and as working or companion dogs in the coastal communities. And there is some genetic legacy of those ancient North American dogs.

There is a type of cancer called canine transmissible venereal tumours (CTVTs) and this was present, genetically, in the North American dog lineage that is all but extinct except for their tumour cells.

It typically persists at quite a low prevalence—1-5 percent of the dog population— and is usually only seen in unmanaged populations of dogs and not generally in the U.K. or the U.S.

Tracing the cancer lineage to ancient North American dogs was a big part of the new study and led to the unfortunate discovery that the tumour cells are likely their only lasting legacy.