A surprising discovery on a small island in the Baltic Sea is changing the way scientists think about the relationship between ancient humans and wolves.
Researchers have identified wolf fossils on the Swedish island of Stra Karsø that date back approximately 3,000 to 5,000 years. The discovery is notable 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 humans must have brought them there.
This study Proceedings of the National Academy of Sciencescarried out by scientists from the Francis Crick Institute, Stockholm University, Aberdeen University and the University of East Anglia. Their findings suggest that prehistoric communities may have managed or domesticated wolves in ways that had been largely unthinkable.
A wolf on an island that he couldn’t reach alone.
The ruins were discovered in the Stra Felvar Cave, an archaeological site in Stra Karso that was frequently used by seal hunters and fishermen during the Neolithic and Bronze Ages. These eras span parts of the Stone Age and early metalworking eras, thousands of years before modern civilization.
Stora Karlsö covers an area of only 2.5 square kilometers and is free of native terrestrial mammals. Because wolves do not have the ability to cross the open ocean and colonize these islands naturally, researchers believe humans must have brought them there, perhaps by boat.
This conclusion alone makes this finding unusual. However, further analysis revealed an even more interesting story.
Proof of living with 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, but researchers found no evidence of canine ancestry.
Despite being genetically a wolf, the animal displayed several traits often associated with living closely with humans.
One important clue came from isotope analysis, a technique that can reveal what an animal ate during its lifetime. The researchers found that wolves consumed large amounts of marine protein, including seals and fish. This closely matches the diet of people living on the island, suggesting that the wolves were likely fed by humans.
The wolf was also smaller than the typical wolf that lives on the mainland. Additionally, one animal showed unusually low genetic diversity. Genetic diversity refers to the extent of genetic variation within an individual or population. Low diversity is often seen in isolated groups and selectively bred animals.
“The discovery of these wolves on a remote island was completely unexpected,” said the study’s lead author, Dr. Linus Gardland-Frink from the University of Aberdeen. “Not only do they have ancestry that is indistinguishable from other Eurasian wolves, but they also appear to have lived and fed with humans in areas only accessible by boat. This paints a complex picture of human-wolf relationships in the past.”
Rethinking the path to domestication
The discovery challenges traditional ideas about how humans and wolves interacted in prehistoric times.
Scientists have long viewed the human-wolf relationship primarily through the lens of dog domestication. Within that framework, wolves coexisted with humans and, through a long process of adaptation to the human environment, gradually evolved into dogs.
The newly discovered wolf doesn’t fit neatly into that story.
Researchers have not yet determined whether the animals were domesticated, kept in captivity, or otherwise managed. However, their presence on an inhabited island strongly suggests a deliberate and ongoing relationship.
“It was a total surprise that it was a wolf and not a dog,” said lead author Pontus Skoglund of the Ancient Genomics Laboratory at the Francis Crick Institute. “This is a provocative case that raises the possibility that, in certain circumstances, humans were able to keep wolves in their habitats and saw value in doing so.”
Genetic clues point to human influence
Additional evidence came from genetic data.
Anders Bergström from the University of East Anglia and co-first author explained that one of the wolves had significantly lower genetic diversity than other ancient wolf specimens.
“The genetic data are interesting. We found that the wolves with the most complete genomes had low genetic diversity, lower than any ancient wolf we have seen to date. This is similar to what is seen in isolated or bottleneck populations, or domesticated organisms. Although we cannot rule out the possibility that these wolves had low genetic diversity for natural reasons, this suggests that humans were interacting with and managing wolves in ways hitherto unimaginable.”
Population bottlenecks occur when populations become very small and genetic diversity decreases. These patterns can occur naturally, but they can also result from human management or selective breeding.
A wolf that may have been taken care of
One of the most interesting discoveries involved a Bronze Age wolf with severe damage to its limb bones.
This injury likely limited the animal’s ability to move and hunt. However, the wolf survived long enough for the condition to leave clear marks on its skeleton.
Researchers say this suggests the animal may have received some level of care or lived in an environment where it didn’t need to hunt large prey to survive.
New insights into ancient human-animal relationships
This research combines osteology, the study of bones, with advanced genetic analysis. Combining these approaches yielded insights that neither method could reveal alone.
“The combination of data reveals new and very unexpected perspectives on Stone Age and Bronze Age human-animal interactions in general, and on wolves and dogs in particular,” says Jan Stroh, professor of osteoarchaeology at Stockholm University.
Overall, this study suggests that the relationship between humans and wolves is much more diverse than scientists once believed. Rather than simply hunting or avoiding wolves, some prehistoric communities may have developed long-term relationships with the animals, managing and caring for them without fully domesticating them.
The discovery marks a forgotten chapter in the history of humans and wolves, suggesting a coexistence experiment that ultimately did not produce the dogs we know today.
