Cave discovery of wolf remains tells a tale of an unexpected relationship with humans.
View from the cave Stora Förvar on the island of Stora Karlsö. Credit: Jan Storå, Stockholm University.
Throughout history, human populations have rarely lived alone, forming sometimes very close relationships with animals, for mutual benefit or companionship.
Pinpointing exactly when the relationship with our canine friends began and how it shaped our own evolution is challenging, as limited ancient wolf and dog remains exist. Attempting to shine light on our co-evolution is a major initiative for Pontus Skoglund, who leads the Crick’s Ancient Genomics Laboratory.
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“How dogs came to be is a major mystery in the human past—wild wolves are dangerous carnivores,” he says. “Ideas range from wolf pups being raised by humans to wolf populations being drawn to food waste and other resources near human settlements. To unravel these mysteries, it's important to have evidence that prehistoric human groups had the capacity to keep wolves.”
In a new study published in the Proceedings of the National Academy of Sciences, Pontus joined forces with researchers at Stockholm University, the University of Aberdeen and the University of East Anglia to analyse the discovery of two 3,000-5,000-year-old wolf remains found in the Stora Förvar cave on the Swedish island of Stora Karlsö.
View towards the Stora Förvar cave on the island of Stora Karlsö. Credit: Jan Apel, Stockholm University.
A small, isolated island, Stora Karlsö is known for intensive use by seal hunters and fishers during the Neolithic and Bronze Ages. It has no native land mammals, meaning that any animals found must have been brought there by people.
Genomic analysis of the 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.
View from the cave Stora Förvar on the island of Stora Karlsö. The cave was explored between 1888 and 1893. The limestone-rich bedrock has contributed to the skeletal material found there being very well preserved. Credit: Jan Storå, Stockholm University.
“The discovery of these wolves on a remote island is completely unexpected,” says Linus Girdland-Flink, a co-study lead based at the University of Aberdeen. “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 they were wolves and not dogs,” says Pontus. “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 Bergstrom at the University of East Anglia and co-study lead, adds, “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.”
Detail of one of the upper arm bones from one of the wolves included in the study. Credit: Jan Storå, Stockholm University.
Osteological analysis of the wolf bones put forward another interesting theory. One of the wolf specimens, dated to the Bronze Age, showed damage in a limb bone, which would have limited its mobility. This suggested to the team that it may have been cared for or was able to survive in an environment where it did not need to hunt large prey.
Jan Storå, Professor of Osteoarchaeology at Stockholm University, believes that the genetic data and osteological findings worked in tandem to help elucidate the findings. “The combination of data has revealed new and very unexpected perspectives on Stone Age and Bronze Age human-animal interactions in general, specifically concerning wolves and dogs,” she says.
For Pontus, this new finding is a reminder that we’re only scratching the surface of understanding human-wolf interactions in prehistory. “These relationships were likely more diverse than previously thought, extending beyond simple hunting or avoidance to include complex relationships that might have looked more like those with our pet dogs today.”
