How Did Two Wolves End Up on This Remote Island Thousands of Years Ago? Researchers Think Humans Brought Them There, Then Cared for Them

The bones were discovered in a cave on the Swedish island of Stora Karlsö. Jan Storå / Stockholm University Dogs are man’s best friend. But exactly how these furry canines came to be humanity’s closest animal companions remains one of science’s mysteries.

One leading hypothesis is that some wolves began hanging around human settlements, where they scavenged leftover food and gradually became less fearful of people. Over many generations, these friendlier wolves evolved into the first dogs. Another possibility is that humans played a more active role, intentionally taking in and breeding certain wolves for traits they found desirable.

Now, researchers have uncovered evidence that suggests our ancestors’ close connections with wolves may have endured long after dogs came on the scene.

Archaeologists identified the millennia-old remains of two gray wolves in a cave on Stora Karlsö, a roughly one-square-mile Swedish island in the Baltic Sea. Stora Karlsö is remote and was never connected to the mainland, and the creatures couldn’t have gotten there on their own. Instead, researchers suspect humans might have intentionally transported them to the island—and likely continued feeding and caring for them afterward.

The discovery, outlined in a paper published in the journal Proceedings of the National Academy of Sciences, was “completely unexpected” and raises new questions about the relationship between wolves and our ancestors, says lead author Linus Girdland-Flink, an archaeologist at the University of Aberdeen, in a statement.

“Not only did they have ancestry indistinguishable from other Eurasian wolves, but they seemed to be living alongside humans, eating their food, and in a place they could have only have reached by boat,” he adds.

The modern saga of the wolves dates back to the late 19th century, when archaeologists excavated the layers of sediment inside Stora Förvar, a cave on the island frequented by seal hunters and fishers during the Neolithic and Bronze Ages. The scientists wondered if several canid bones found at the site might have come from wolves.

Decades later, researchers decided to revisit that old question, which caught their attention because “there is no evidence in the archaeological record that wolves ever lived on these islands,” Girdland-Flink tells ZME Science’s Mihai Andrei.

But telling wolves and dogs apart by their bones alone can be challenging. “A lot of very, very early putative dogs, when you run the DNA on them, they actually come out as wolves,” William Marsh, a paleogeneticist at the Natural History Museum of London who was not involved with the research, told National Geographic’s Bethany Brookshire earlier this year.

So, the scientists turned to genetic testing, which confirmed the two canids found on Stora Karlsö were indeed wolves, without a hint of dog ancestry. That was a “complete surprise,” study co-author Pontus Skoglund, a geneticist at the Francis Crick Institute, says in the statement.

Even so, the creatures showed clear signs they had been living closely among humans, including enjoying a diet rich in seals and fish—the same foods people were eating.

Additionally, both of the creatures were relatively small. And one of the wolves’ genes indicates it might have been selectively bred. That same creature also suffered some sort of injury or disease that likely limited its mobility, which suggests it wasn’t surviving by scavenging or hunting.

“This suggests that the people who used or occupied Stora Karlsö at least occasionally interacted with wolves in a manner that implies they exerted some degree of control over these animals,” Girdland-Flink tells ZME Science.

Scientists think dogs have been domesticated for at least 14,000 to 16,000 years, splitting off from some unidentified wolf population. But the 3,000- to 5,000-year-old wolf remains from Stora Karlsö hint that the story didn't end there, suggesting humans maintained relationships with wolves long after the emergence of dogs.

The humans of Stora Karlsö may not have successfully domesticated gray wolves, but they seem to have coexisted with them—and, possibly even, managed and cared for them.

“This is a provocative case that raises the possibility that in certain environments, humans were able to keep wolves in their settlements, and found value in doing so,” Skoglund says in the statement.

Sarah Kuta is a writer and editor based in Longmont, Colorado. She covers history, science, travel, food and beverage, sustainability, economics and other topics.