Man's best friend was also the first animal to be domesticated. On that point, archaeologists overwhelmingly agree. Yet the origin of dogs (as we know them today) has always been a controversial area of research. From wild wolves, early humans bred a new type of canine that was designed to suit their own needs. This might have happened as recently as 15,000 years ago or as far back as 32,000 years ago.
And it likely occurred more than once. Laurent Frantz at Queen Mary University of London, Durham University's Angela Perri in the U.K., and Greger Larson at the University of Oxford were among the archaeologists who co-authored a groundbreaking study that the journal Science published in 2016. Their team compared the DNA of 59 ancient dog specimens with genome information from more than 2,500 modern pooches. Noticing a deep genetic split between select breeds, the scientists concluded that two separate wolf populations in east Asia and central Eurasia independently gave rise to domestic dogs. If this is correct, modern dogs have a two-pronged origin story.
In a new paper — published by the journal Science on July 5, 2018 — Frantz, Larson, Perri and many of their colleagues next tackled the mysteries of American dog breeds. According to the researchers' findings, these New World American dogs are genetically newer than you might suppose.
Early Dogs in the Americas
When Christopher Columbus reached the Caribbean in 1492, there were no sheep, pigs, cattle or horses in the Americas. The only domesticated creature that was present in both hemispheres by that point in time was our good pal, the dog.
Some of the first people to ever settle the Americas apparently took their dogs along as they trekked across the Bering Strait between 10,000 and 15,000 years ago. DNA evidence from ancient dog bones recovered in Alaska, Peru, Mexico and Bolivia backs this up. Nobody knows what function the traveling pooches would've served, but they may have helped their human partners transport goods or hunt down game animals. (Side note: Why mankind decided to try and domesticate dogs in the first place is another big topic of debate.)
Frantz and his team wanted to learn more about the history of canines in the New World. For this new study, the researchers harvested genetic information from 71 different dog specimens recovered at archaeological sites in Siberia and North America.
It's previously been suggested that the pre-Columbian or "pre-contact" — dogs who lived alongside Native Americans were the direct descendants of New World wolves. However, the recent genetic survey points to Siberian wolves as their most probable ancestors. But that's not all. The researchers also found that America's pre-Columbian dogs had unique genetic signatures, the likes of which cannot be found in any other group of canines that we humans have ever bred.
Then, in a short amount of time, those distinctive pups basically vanished.
Genetics, Conquistadors and Doggy Displacement
The late 15th century saw the dawn of European colonialism in the New World. Explorers from Spain, France, England and other countries brought their own Eurasian dogs with them while journeying through the western hemisphere. Columbus himself set sail with 20 mastiffs and greyhounds on his 1493 return trip to the Caribbean; unfortunately, those animals were used to horrific effect as attack dogs.
Apparently, the newcomers left a huge mark. The newly-published data shows that existing dog breeds of American origin, such as chihuahuas and Labrador retrievers, are much closer genetically to the Eurasian dogs brought over by Old World expatriates than they are to the New World's pre-contact pooches. Today, the canine gene pool contains almost no trace of the pre-contact dogs from the New World before the Europeans landed. We may never know what happened to the pre-Columbian dogs who lived alongside Native Americans for so many millennia. Perhaps they were actively hunted down or killed off by foreign diseases brought over by the Europeans. (Sounds familiar doesn't it?)
"This study demonstrates that the history of humans is mirrored in our domestic animals," professor Greger Larson, director of the Palaeo-BARN at Oxford and senior author of the study, said in a press release. "People in Europe and the Americas were genetically distinct, and so were their dogs. And just as indigenous people in the Americas were displaced by European colonists, the same is true of their dogs."
A Cancerous Epilogue
All this is not to say that the pre-Columbian dogs have left nothing behind for posterity. Apart from the fossils we've discussed, the canines figure prominently in Native American artwork. To see some of this, look no further than the western Mexican state of Colima, which is famous for the 2,000-year-old ceramic canines found in its ancient tombs.
But these pre-Columbian dogs may also be responsible for a medical malady well-known to veterinarians across the globe. Right now, dogs from Alaska to Australia and from Spain to Swahili are at risk of contracting canine transmissible venereal tumors, or CTVT for short. This is a transferrable cancer that dogs usually pass on to one another as they mate, but it can also be spread via licking or sniffing. Cauliflower-shaped tumors around the genitals are its usual calling card.
What does a malignant cancer have to do with a dog lineage that for all intents and purposes doesn't exist anymore? Well, as Science reports, genomic evidence gathered by Frantz, Larson, Perri and their crew suggests that the first dog to ever contract CTVT — the "patient zero" if you will — was akin to the New World pre-Columbian canines. A mutated version of the DNA from that so-called "founder dog" is now present in every living pooch who suffers from these tumors. Not all legacies are romantic, you know.