5,000-year-old wolves found on remote island rewrite what we know about domestication

Researchers have identified wolf remains dating back roughly 3,000 to 5,000 years on the Swedish island of Stora Karlsö. The finding is remarkable because the island is isolated and has no native land mammals. The wolves could not have reached the island on their own, leading researchers to conclude that people must have transported them there.

The study, published in Proceedings of the National Academy of Sciences, was conducted by scientists from the Francis Crick Institute, Stockholm University, the University of Aberdeen, and the University of East Anglia. Their findings suggest that prehistoric communities may have been managing or keeping wolves in ways that have rarely been considered before.

Wolves on an Island They Could Not Reach Alone

The remains were uncovered in Stora Förvar cave, an archaeological site on Stora Karlsö that was heavily used by seal hunters and fishers during the Neolithic and Bronze Ages. These periods span parts of the Stone Age and early metalworking eras, thousands of years before modern civilization.

Stora Karlsö covers just 2.5 square kilometers and lacks native terrestrial mammals. Because wolves are not capable of naturally colonizing such an island across open sea, researchers believe humans must have brought the animals there, likely by boat.

That conclusion alone makes the discovery unusual. But further analysis revealed an even more intriguing story.

Evidence of Life Alongside Humans

Scientists examined the remains of two canids, a group that includes wolves, dogs, foxes, and related animals. Genetic testing confirmed that both specimens were wolves rather than dogs, and the researchers found no evidence of dog ancestry.

Despite being genetically wolf, the animals displayed several characteristics often associated with living closely with people.

One important clue came from isotope analysis, a technique that can reveal what an animal ate during its lifetime. The results showed that the wolves consumed large amounts of marine protein, including seals and fish. This closely matched the diet of the people living on the island, suggesting the wolves were likely being fed by humans.

The wolves were also smaller than typical wolves living on the mainland. In addition, one animal showed unusually low genetic diversity. Genetic diversity refers to the range of genetic variation within an individual or population. Low diversity is often seen in isolated groups or in animals that have been selectively bred.

"The discovery of these wolves on a remote island is completely unexpected," said Dr. Linus Girdland-Flink of the University of Aberdeen, a lead author of the study. "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. This paints a complex picture of the relationship between humans and wolves in the past."

Rethinking the Path to Domestication

The findings challenge traditional ideas about how humans and wolves interacted in prehistory.

Scientists have long viewed the relationship between people and wolves largely through the lens of dog domestication. In that framework, wolves gradually evolved into dogs through a long process of living alongside humans and adapting to human environments.

The newly discovered wolves do not fit neatly into that story.

Researchers cannot yet determine whether the animals were tame, kept in captivity, or managed in some other way. However, their presence on an island inhabited by people strongly suggests an intentional and ongoing relationship.

"It was a complete surprise to see that it was a wolf and not a dog," said Pontus Skoglund of the Ancient Genomics Laboratory at the Francis Crick Institute and senior author. "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."

Genetic Clues Point to Human Influence

Additional evidence came from the genetic data.

Anders Bergström of the University of East Anglia and co-lead author explained that one of the wolves possessed exceptionally low genetic diversity, even when compared with other ancient wolf specimens.

"The genetic data is fascinating. We found that the wolf with the most complete genome had low genetic diversity, lower than any other ancient wolf we've seen. This is similar to what you see in isolated or bottlenecked populations, or in domesticated organisms. While we can't rule out that these wolves had low genetic diversity for natural reasons, it suggests that humans were interacting with and managing wolves in ways we hadn't previously considered."

A population bottleneck occurs when a group becomes very small, reducing genetic variation. Such patterns can emerge naturally, but they can also result from human management or selective breeding.

A Wolf That May Have Been Cared For

One of the most intriguing discoveries involved a Bronze Age wolf that suffered from severe damage to a limb bone.

The injury would likely have limited the animal's ability to move and hunt effectively. Yet the wolf survived long enough for the condition to leave a clear mark on its skeleton.

Researchers suggest this may indicate that the animal received some level of care or lived in circumstances where it did not need to hunt large prey to survive.

New Insights Into Ancient Human-Animal Relationships

The study combined osteology, the study of bones, with advanced genetic analysis. Together, these approaches provided insights that neither method could have revealed on its own.

"The combination of data has revealed new and very unexpected perspectives on Stone Age and Bronze Age human-animal interactions in general and specifically concerning wolves and also dogs," says Jan Storå, Professor of Osteoarchaeology at Stockholm University.

Overall, the research suggests that relationships between humans and wolves were far more varied than scientists once believed. Rather than simply hunting wolves or avoiding them, some prehistoric communities may have formed long-term relationships with the animals, managing and caring for them without fully domesticating them.

The discovery points to a forgotten chapter in the history of humans and wolves, one that hints at experiments in coexistence that never ultimately produced the dogs we know today.