Scientists have found wolf remains, thousands of years old, on a small, isolated island in the Baltic Sea – a place where the animals could only have been brought by humans. The study, published in Proceedings of the National Academy of Sciences by researchers at the Francis Crick Institute, Stockholm University, the University of Aberdeen and the University of East Anglia, suggest that grey wolves may have been managed or controlled by prehistoric societies.
The discovery of the 3,000–5,000-year-old wolf remains was made in the Stora Förvar cave on the Swedish island of Stora Karlsö, a site known for its intensive use by seal hunters and fishers during the Neolithic and Bronze Ages. The island, which covers only 2.5 square kilometres, has no native land mammals, meaning that any such animals must have been brought there by people.
Genomic analysis of two canid remains confirmed they were wolves, not dogs, with no evidence of dog ancestry. However, they exhibited several traits typically associated with life alongside humans. Isotope analysis of their bones revealed a diet rich in marine protein, such as seals and fish, aligning with the diet of the humans on the island and suggesting they were provisioned. Furthermore, the wolves were smaller than typical mainland wolves, and one individual showed signs of low genetic diversity, a common result of isolation or controlled breeding.
"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."
The finding challenges the conventional understanding of wolf-human dynamics and the process of dog domestication. While it remains unclear if these wolves were tamed, kept in captivity, or managed in some other way, their presence in a human-occupied, isolated environment points to a deliberate and sustained interaction.
"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."
Anders Bergström of the University of East Anglia and co-lead author, commented: "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."
One of the wolf specimens, dated to the Bronze Age, also showed advanced pathology in a limb bone, which would have limited its mobility. This suggests it may have been cared for or was able to survive in an environment where it did not need to hunt large prey.
The combination of osteology and genetic analyses have provided unique information not available separately. "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.
The study suggests that human-wolf interactions in prehistory were more diverse than previously thought, extending beyond simple hunting or avoidance to include complex relations and interactions that, in this case, mirrors new aspects of domestication without leading to the canines we know as dogs today.
