Researchers Track Changes in Size of Europe’s Dogs

European dogs doubled in size from 8000 to 2000 years ago, a new study suggests. The beefing up may have helped our canine pals protect sheep from bears and even their direct ancestor—the gray wolf.

It’s “important” research, says Robert Losey, an archaeologist at the University of Alberta, Edmonton, who specializes in ancient human-animal relationships but was not involved with the work. “It’s one of the few long-term studies based in Europe looking at trends in dog size over time.”

Dogs were domesticated between 15,000 and 30,000 years ago. Little is known about the size and roles of the earliest pups, though they were likely smaller than the gray wolves they came from.

Scientists have speculated that ancient dogs may have helped humans hunt and pull sleds.

To see how the size—and jobs—of dogs changed over time, Martin Welker, a zooarchaeology curator at the Arizona State Museum, and his colleagues examined the remains of 14 dogs uncovered from ancient human settlements in Croatia.

They also incorporated data from another 45 ancient dogs, some from Croatia and some from neighbouring countries. The remains dated from about 8000 years ago in the Neolithic (or later Stone Age) to the Roman period, about 2000 years ago.

Dogs had lived in the region before, but the first Neolithic farmers, who arrived in the area from Anatolia and the Middle East, brought a new breed with them.

These new animals averaged about 15 kilograms—roughly the size of a border collie, the scientists found—though this was long before most of today’s breeds evolved.

By the Bronze Age, which started roughly 6000 years ago in this region, the average mass increased to about 17 kilograms. And by Roman times, the weight of the average dog had jumped to 24 kilograms, the team concluded last month in the Journal of Archaeological Science: Reports.

Historical documents—including ancient Roman records giving advice to farmers on herding and guard dogs—suggest even bigger dogs at the time, reaching at least 32 kilograms, nearly the weight of today’s great Pyrenees dogs.

Great Pyrenees are still used to guard European livestock—and, indeed, the researchers saw an evolution in responsibilities as ancient dogs got bigger.

Isotope analysis of the teeth of Neolithic sheep, which can reveal ancient diets, suggests that, as time went on, they grazed higher in the mountains. “In doing so, you expose them to larger risk from predators like wolves and bears,” Welker says, making guard dogs important.

Not every dog was a hulking protector: The Romans may have been the first people to breed lapdogs, according to depictions on murals and other evidence.

Researchers have focused on hunting dogs but know less about what happened when people began farming, which makes this study exciting, says Angela Perri, an expert on ancient dogs with PaleoWest, a private archaeology firm. Perri wasn’t involved with the study.

Guard dogs are key to that story, and they had “staying power,” she says. “Hunting dogs and sledding dogs now are pretty rare, but people are still using herding and livestock guarding dogs everywhere.”