In the waning days of the last ice age, when humans were still hunting with spears and using cave walls as canvases, a hot new trend was spreading through the Paleolithic landscape.
By roughly 14,000 years ago, hunter-gatherer societies across Europe had discovered dogs, scientists reported in two new papers, which were published Wednesday in the journal Nature. The studies provide the first definitive genetic evidence that dogs existed during the Paleolithic period, before humans developed agriculture.
The researchers, who used several approaches to analyze DNA extracted from ancient canine specimens, identified Paleolithic dogs at five different archaeological sites in Europe and Western Asia. The oldest of these dogs lived about 15,800 years ago, pushing back the oldest known genetic evidence of dogs by nearly 5,000 years.
These early dogs came from sites that extend from Britain to Turkey, and were associated with several very different hunter-gatherer populations. But the dogs themselves were closely related. Across the five sites, the dogs were more genetically similar than the humans were, the researchers found.
“The people are so different, but the dogs are very much the same,” said Greger Larson, a paleogeneticist at the University of Oxford and one of the authors on both new studies, which were conducted by large, international scientific teams.
The finding suggests that these early human societies were exchanging dogs or acquiring them from one another.
“It is kind of the equivalent of a new blade or a new point or a new kind of material culture or art form or something, where everybody’s getting really excited about having this fun new thing around.” Dr. Larson said. “And it’s useful and it’s interesting and it’s probably cute.”
The research provides new insight into the early history of dogs, as well as the genetic legacy and the interspecies relationship that extends to today.
“It’s really a major step forward in advancing our knowledge of humans and dogs,” said Elaine Ostrander, a canine genomics expert at the National Human Genome Research Institute who was not involved in the research.
Dog bones
Dogs descended from ancient wolves, but exactly when and where they first emerged remains a subject of intense scientific debate. Some scientists have suggested that the size and shape of ancient canine specimens indicate that dogs and wolves diverged more than 30,000 years ago.
But such remains can be tricky to identify definitively. In some cases, geneticists have determined that canine remains that initially appeared to be from dogs actually belonged to now-extinct wolves. In others, they haven’t been able to recover enough DNA to make a conclusive call about species. Before the new research, the oldest definitive dog DNA dated back just 10,900 years.
In one of the new studies, scientists assembled and analyzed the complete genomes of eight ancient canines and compared them with ancient and modern wolves and dogs. Six of the animals had genomes that resembled those of dogs, they concluded. And two of those dogs dated back to the Paleolithic era — a 15,800-year-old dog from Pinarbasi, Turkey, and a 14,300-year-old dog from Gough’s Cave, an archaeological site in Britain.
The genomes from those two Paleolithic dogs became “the Rosetta Stone, for lack of a better term, that then unlocked all of the stuff that we already had in our database,” said Lachie Scarsbrook, a paleogeneticist at the University of Oxford and an author of one of the studies.
That database had three other ancient canines, their species unknown. The genetic data on these animals was incomplete: Scientists had previously sequenced only the DNA from their mitochondria, representing a small fraction of their total genetic material. (A vast majority of an animal’s DNA is stored in the cell nucleus.)
But the mitochondrial DNA from these three unknown canines was so similar to the mitochondrial DNA from the British and Turkish dogs that the scientists concluded that these animals were probably Paleolithic dogs, too. They were 14,000 to 14,300 years old and came from sites in Germany, Italy and Switzerland.
In the second paper, scientists used a different approach to extract and analyze DNA from more than 200 ancient canine remains, including samples from the same site in Switzerland. They analyzed nuclear DNA from the same canine that the first team had identified as being a Paleolithic dog and reached the same conclusion.
Paleolithic pups
Overall, the researchers found evidence of genetically similar Paleolithic dogs at five different archaeological sites that were associated with people from three different hunter-gatherer cultures: the Magdalenian, Anatolian and Epigravettian peoples.
These are “utterly different cultures,” said Ian Barnes, a paleogeneticist at the Natural History Museum in London and an author of one of the studies. “Presumably linguistically different, completely culturally different, ecologically different, with the same animal. So how does that square up? How does that happen?”
One possibility, the researchers proposed, is that dogs spread through Europe as the Epigravettian culture expanded across the continent roughly 16,000 years ago, and Epigravattian people passed dogs along to other hunter-gatherer populations they encountered.
How these dogs slotted into these societies remains unclear. “What these animals were doing for them, or whether they were just following them, this we don’t really know,” said Laurent Frantz, a paleogeneticist at Ludwig Maximilian University of Munich and an author of both studies. But given the varied human cultures and environments, it’s possible that these genetically similar dogs were performing different jobs in different human populations.
That means that while humans would later turn dogs into highly specialized tools, optimized to pull sleds or wriggle into badger holes, these Paleolithic dogs might have been more like “a Swiss army knife,” Dr. Larson said. “The dogs might be doing different things, but the dogs themselves are all the same color, same height, same genomic ancestry.”
These hunter-gatherer societies did appear to have close relationships with the dogs, the researchers reported. At some sites, for instance, there was evidence that humans had perhaps provided these early dogs with food and, in death, had treated their bodies like human ones.
“That indicates to us a very, very close interaction,” said William Marsh, a paleogeneticist at the Natural History Museum and an author of one of the studies.
And the legacy of these Paleolithic dogs most likely lives on. When the first farmers began to arrive in Europe — migrating from southwestern Asia roughly 9,000 years ago — they brought their own dogs with them. “There was basically a mixing of all the different dogs from both hunter-gatherer groups and farming groups,” said Pontus Skoglund, a paleogeneticist at the Francis Crick Institute in London who was an author of both studies.
Europe’s farmers thus ended up with dogs that still carried a lot of ancestry from the dogs that had once lived alongside the continent’s hunter-gatherers. Modern European dogs can also probably trace much of their ancestry back to those canines, the researchers said.
Still, the biggest questions surrounding the origins of the dog remain unanswered.
“It’s very exciting that we have this first view of Paleolithic, really early dog ancestry,” Dr. Skoglund said.
“But the question of where dogs come from, and who were these people that domesticated them or started to build this bond,” he added, “we’re still trying to find out.”
Emily Anthes is a science reporter, writing primarily about animal health and science. She also covered the coronavirus pandemic.
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