When 19th century naturalists and explorers first encountered the dogs of Native Americans, they were shocked by the canines’ wolflike appearance. The animals were large and strong, and they didn’t bark—they howled. “If I was to meet with one of them in the woods,” remarked John James Audubon, “I should most assuredly kill it.”
But today, these dogs and their kin are nowhere to be found, their genetic legacy wiped from the genomes of all living canines. Now, DNA recovered from several of these ancient animals has revealed where America’s first dogs came from—and how they may have disappeared.
“It’s really great research,” says Jennifer Raff, an anthropological geneticist at the University of Kansas in Lawrence and an expert on the peopling of North America. The work supports emerging evidence that the first Americans did not bring dogs with them. Instead, says Raff, the animals may have come thousands of years later.
In the 1960s and 1970s, archaeologists excavated two sites in western Illinois, where ancient hunter-gatherers collected shellfish from a nearby river and stalked deer in surrounding forests. These people also appear to have buried their dogs: One was found at a site known as Stilwell II, and four at a site called Koster, curled up in individual gravelike pits.
Radiocarbon analysis of the bones reveals that they are around 10,000 years old, making these canines the oldest dogs known in the Americas, researchers report on the bioRxiv server. It also makes these the oldest solo dog burials anywhere in the world.
The Stilwell II dog was about the size of an English setter, whereas the Koster dogs were smaller and slenderer, says the study’s lead author, Angela Perri, a zooarchaeologist at Durham University in the United Kingdom. “It wouldn’t be surprising if they were all used as hunting dogs.” But where did they come from in the first place?
A second study, published today in Science, may have the answer. A large, international team of researchers sequenced DNA from the mitochondria, or cellular power plants, of 71 North American and Siberian dog bones—including from one of the Koster dogs—dated from about 10,000 to 1000 years ago. When they compared this material, which is passed down only by the mother, to that of 145 modern and ancient dogs, they discovered that the ancient American dogs have a genetic signature not found in any other canines.
“They form their own group that has their own story,” says Perri, also a lead author on the Science paper. That means the wolflike dogs Audubon encountered were indeed genetically distinct from European ones.
These “precontact dogs,” as the team calls them, are most closely related to 9000-year-old dogs from Russia’s Zhokhov Island, hundreds of kilometers north of the Siberian mainland. By assuming a relatively constant DNA mutation rate and using it as a “molecular clock,” the team concludes that the two groups of dogs may have shared an ancestor nearly 16,000 years ago. It’s still unclear exactly where or when dogs arose, but it could have been around that time.
Taken together with archaeological findings, the data suggest that the first dogs may have come to the Americas from Siberia thousands of years after the first people, says team leader Laurent Frantz, an evolutionary geneticist at the University of Oxford in the United Kingdom. Humans likely entered the Americas around 16,000 years ago over the Bering land bridge, which connected Siberia to Alaska. The bridge disappeared about 11,000 years ago—by which time dogs must have already made it over, Frantz says.
Dogs may have hung out with people in Alaska for a while, or a few may have traveled with humans to the interior of North America, where they ended up in sites like Koster and Sitwell II. “People were moving around a lot,” Raff says. Once they saw how useful dogs were—for tracking deer, hauling supplies, and guarding camps—humans might have started bringing more of them along for the journey.
“It’s a tidy story that adds some grounding for what people thought was happening,” says Melinda Zeder, an archaeozoologist at the Smithsonian Institution’s National Museum of Natural History in Washington, D.C. But she notes that molecular clocks are just an approximation and other mysterious bones found in Siberia and the Yukon may belong to dogs, possibly pushing their arrival in the Americas earlier by thousands of years. “It’s hard to draw a firm conclusion.”
Additional analysis of the nuclear genome—inherited from both parents—of seven precontact dogs supports the idea that they are genetically distinct. Their closest living relatives are Arctic breeds such as Alaskan malamutes and Siberian huskies. These modern dogs may have come from the same Siberian source population as the precontact dogs, but thousands of years later. “If you have an Arctic dog, you likely have an old dog,” Perri says. “If you have any other dog, it probably came from Europe or Asia a lot more recently.”
That goes even for supposedly ancient dogs like the hairless Mexican Xoloitzcuintli, which is believed to have been around for thousands of years. “Today’s dogs may look the same as those dogs,” Frantz says. But according to the samples taken so far, “their genetics are totally different.”
Indeed, the team found almost no genetic trace of precontact dogs in any modern dogs. “By and large, their genetic signature has vanished,” Perri says. Both she and Frantz speculate that, just as European colonists wiped out large numbers of Native Americans with their diseases, the European dogs may have devastated American dogs even more. Europeans also may have feared these wild-looking dogs, as Audubon did, and tried to wipe them out, Perri says.
The only trace of these early dogs may survive in a sexually transmitted canine cancer, which has retained the genetic signature of the first dog it plagued. When the team compared the genomes of two of these tumors to modern and ancient dog genomes, the DNA most closely resembled that of precontact dogs, perhaps one that lived about 8000 years ago. “It’s fascinating,” says Frantz, “but at the moment it doesn’t tell us much about the history of America’s first dogs.”
If people didn’t bring dogs over with them right away, it could be because they didn’t know how useful they would be. Or it could simply be that dogs didn’t exist yet. When this alliance did form in the Americas, it likely mirrored one taking place all over the world, where dogs were used for hunting, guarding, or simple companionship. “It’s insane that we would have started a relationship with an animal that could hurt us and compete with us,” Perri says. “There must have been a good reason.”
*Correction, 5 July, 7 p.m.: This story has been updated to reflect the fact that the first study is only available on bioRxiv. Angela Perri's affiliation has also been updated.
*Correction, 1 August, 3:50 p.m.: An earlier version of this story stated that the Xoloitzcuintli came from South America. It is actually from Mexico.