Ancient DNA recovered from pre-historic dogs paints a picture of how canines and humans discovered North America—side by side
In brief: Ancient DNA studies using advanced sequencing technologies are helping researchers learn more about when wolves became dogs, how the process occurred and how domesticated dogs and humans traveled side by side across the Bering Strait and into the heart of North America.
When and how wolves became dogs has been a matter of ongoing scientific investigation, and now, new DNA sequencing efforts have gone a step further in answering that question.
But first, let’s explore in greater detail the dog-wolf connection.
When did wolves become dogs?
If you’ve ever looked into the eyes of, say, a Siberian husky, then it’s pretty obvious that dogs bear a strong relation to wolves. But so do poodles and chihuahuas.
Gray wolves and dogs diverged from an extinct wolf species between 15,000 and 40,000 years ago, and that process was likely aided by human efforts of domestication. Genetic studies have made several suggestions for where that domestication occurred, from Europe to Mongolia.
A 2017 study in Nature said domestication could have taken place as long as 40,000 years ago, while DNA from two Neolithic dog fossils found in Germany showed that dogs from that period—4000 to 7000 years ago—were similar to modern European pet dogs, suggesting there was likely only a single domestication event. That was challenged by a separate study that analyzed ancient dog DNA found in Ireland and found evidence that domestication took place in Asia.
How did wolves become dogs?
There is as much debate with how wolves became dogs as there is about when it happened.
Early theories revolved around the idea that humans captured wolf pups and raised them as pets while gradually domesticating them. A second, more recent theory, posited that wolves domesticated themselves to survive among humans since they were both competing for the same resources.
Genetic testing from 2017 suggested that gene variations may have played a role in causing some wolves to befriend humans, with those variations focused on molecular features that could shape behavior. Those features could also explain how some breeds developed and coloration differences appeared.
Is this the oldest domesticated dog in the Americas?
Now comes a study that purports to have identified the oldest known domesticated dog in the Western Hemisphere.
The finding, published in The Royal Society Publishing, is based on DNA studies of a bone fragment found in a cave in southeast Alaska. Researchers originally thought it belonged to a bear but now understand it comes from a dog.
The breakthrough comes in part courtesy of advanced mitochondrial DNA (mtDNA) sequencing and mtDNA target enrichment that revealed clues that might have been missed if the research had been conducted just a decade earlier. The advanced work included improvements in DNA extraction, contamination correction, quick organism assessment, and the building of a database that can be used to protect broad patterns.
This finding would support earlier research which suggested that humans and dogs left Eurasia together as glaciers advanced and crossed the Bering Land Bridge. The bone fragment found in Alaska was genetically tied to older Siberian dogs.
It also fits neatly (or as neatly as these sorts of findings get) with early dog bones found further to the south, including those from a Midwest genetic group and others in Alabama and Missouri. Taken together, they are aiding in the creation of a dispersal map of both humans and canines that extends south from the Bering Strait into what is now the United States.
The fragment of the dog bone further adds to knowledge about how humans traveled from Alaska to the interior of North America. Previous theories had suggested they moved down an ice-free corridor which ran through central Alaska and central British Columbia. The recent Alaska finding, however, puts them along the coast, island-hopping their way south.
“Because the estimated split date of precontact dogs from East Siberian dogs is comparable to the suggested early human migration to North America, it seems likely that dogs were brought with humans during these earliest migrations along the North Pacific coastal route,” wrote the authors of The Royal Society Publishing article. “However, as with humans, physical remains are only known from much later in the subfossil record, and we cannot exclude the possibility that precontact dogs occupied Beringia during the Last Glacial Maximum, followed by later migration southward along the coast.”
With sequencing practices evolving, new bone finds could further illustrate the history of domesticated dogs and how they migrated with humans across Asia and into North America.
Dog lovers may be left wondering: Exactly what dog breed was it that was found in Alaska? That remains to be seen.
“American Pre Contact Dogs were almost entirely replaced by later Inuit sled dogs and European breeds that arrived with European colonists, leaving only a minor Pre Contact Dog genetic legacy among modern dogs,” researchers wrote. “Future nuclear genome analyses of precontact dogs, including (the cave specimen in question), will permit more complete insights of the fate of Pre Contact Dogs.”