Foxes were once humans' best friends, study says

An artist's reconstruction depicts the extinct fox species Dusicyon avus, which scientists believe may have been domesticated 1,500 years ago by hunter-gatherers in what’s now Patagonia in Argentina. (Juandertal via CNN Newsource)

In an ancient grave in what’s now northwestern Argentina, a person was buried with a canine companion — but this animal friend wasn’t a dog, according to new research. The burial held the skeleton of a type of canid that may have once competed with dogs for human affection: a fox.

Humans and dogs have a long history. The relationship between the two species is tens of thousands of years old. However, a fresh analysis of evidence from a Patagonian burial dating back about 1,500 years hints at a similar close connection between a hunter-gatherer in southern South America and the large extinct fox species Dusicyon avus.

Archaeologists originally uncovered the near-complete D. avus skeleton buried alongside a human at Cañada Seca, a site in northern Patagonia, in 1991. There were no cut marks on the bones, so the fox hadn’t been eaten, said Dr. Ophélie Lebrasseur, a researcher with the Wellcome Trust Palaeogenomics and Bio-Archaeology Research Network at the University of Oxford’s School of Archaeology in the United Kingdom.

An in-depth analysis of ancient DNA and radiocarbon dating confirmed the fox’s species and age, and examination of collagen in the fox’s remains revealed that it ate the same food that this group of humans did. Along with the skeleton’s placement in the grave, the animal’s diet suggested that the fox was tame and may have been kept as a pet, scientists reported Wednesday in the journal Royal Society Open Science.

The discovery adds to a growing body of evidence from burial sites on other continents indicating that individual foxes were tamed by humans and shared a connection based on companionship.

The fox and hunter-gatherer society

D. avus lived from the Pleistocene Epoch (around 2.6 million to 11,700 years ago) into the Holocene, becoming extinct about 500 years ago. It was roughly the size of a modern German shepherd but far less bulky, weighing up to 33 pounds (15 kilograms).

“In general, Dusicyon avus has a carnivorous kind of diet,” said Lebrasseur, who co-led the study with Dr. Cinthia Abbona, a researcher with Argentina’s National Scientific and Technical Research Council. But when the scientists tested the fox skeleton from the burial, they found that its diet was less carnivorous than expected, and more similar to the diets of humans.

“That suggests either the community was feeding it, or it was around the community and feeding on the kitchen refuse,” Lebrasseur told CNN. “It would suggest that there’s a closer relationship and integration of the canid within the society.”

The notion of foxes as pets in South America aligns with evidence from other fox burials in Europe and Asia, said Dr. Aurora Grandal-d’Anglade, a paleobiologist at the Universidade da Coruña in Spain. Grandal-d’Anglade, who was not involved in the new study, previously described Bronze Age graves in the Iberian Peninsula that included dozens of dogs and four foxes buried alongside people. Researchers found that the foxes had been arranged much like the dogs were, suggesting that they, too, were companions for humans.

“There is no reason why foxes could not be domesticated,” Grandal-d’Anglade told CNN in an email. “We know that humans in many completely different societies often keep domestic animals (not only canids, but e.g. monkeys, birds, reptiles) simply as companion animals. When viewed in this light, more and more sites appear where foxes seem to have played the role of pet animals.”

Finding D. avus in a human grave was surprising for another reason — while the species was once widespread across southern South America, it was previously unknown in this part of Patagonia. Hunter-gatherers who lived in the region typically stayed within a range of about 44 miles (70 kilometres), so they likely encountered the friendly fox within that range, according to the study.

“The Dusicyon avus must have been part of the nearby vicinity, to be able to be integrated within the community,” Lebrasseur said.

What fox burials reveal about 'man's best friend'

The analysis also shed light on what drove the foxes to extinction — or rather, what didn’t. One hypothesis suggested that the foxes interbred with dogs that European colonizers introduced to South America, and that interbreeding eventually caused the foxes’ lineage to peter out. But the fox's DNA told a different story, the study authors reported.

“Based on what we were able to recover and the technique that we developed at Oxford a few years ago, we were able to suggest that the hybridization between domestic dogs and Dusicyon avus would not have been able to produce fertile offspring,” Lebrasseur said.

However, it’s still possible that dogs weren’t entirely innocent in the foxes’ decline. With a similar diet to D. avus, dogs may have helped speed the foxes’ extinction by outcompeting them. Dogs could also have carried and transmitted diseases that sickened the foxes, Lebrasseur added.

Experts often explain dog domestication as something that happened because humans realized that they could put dogs to work as hunters or herders, Grandal-d’Anglade said. But the D. avus skeleton at Cañada Seca and other fox burials hint that an animal didn’t need to be a useful worker to be nurtured by humans — it could simply be a friend.

“The proliferation of canids of different species in close relationship with humans seems to indicate that in principle it was a relationship of affection, of companionship,” Grandal-d’Anglade said. “The fact that we find them in so many different societies and on different continents indicates that keeping animals for companionship, and not only as working or meat animals, is an ancestral trait in humans.”

Mindy Weisberger is a science writer and media producer whose work has appeared in Live Science, Scientific American and How It Works magazine.