For 6 weeks in the summer of 2010, a hardy band of scientists floated down a river on the Taymyr Peninsula, a bare hump of Siberia that juts out into the Arctic Ocean. They were on a hunt for ice age treasures: animal bones that had tumbled from the melting permafrost along the riverbank. There, among mammoth tusks and other remains, Love Dalén spotted what he thought was a reindeer rib. But when the evolutionary geneticist analyzed it back at the Swedish Museum of Natural History in Stockholm, he realized that the 5-cm-long specimen belonged instead to a wolf—one that could shed new light on the history of dog domestication. “This will be one of the critical pieces,” says Robert Wayne, an evolutionary biologist at the University of California, Los Angeles, who was not involved with the work.
Humans domesticated dogs long before any other animal, yet researchers don’t agree on where or when this happened. One study of the DNA of modern dogs and wolves suggests that dogs arose less than 16,000 years ago in Southeast Asia, but another genetic analysis of ancient dogs and wolves pegs the event to Europe as long as 32,000 years ago. Archaeological studies have been similarly contentious, with some groups claiming that Russian and Belgian skulls dated to about 30,000 years ago represent the world’s first dogs, whereas others argue that the oldest definitive dog skulls are 16,000-year-old craniums found in Russia and Germany.
Dalén hopes the new study will put some of the debate to rest. When he and his colleagues dated the small Taymyr bone and sequenced its genome, they discovered that the specimen belonged to a male wolf that lived about 35,000 years ago. The DNA, when compared with that of modern and ancient dogs and wolves, indicated that this individual lived during a critical period in canine history, when an ancient population of wolves divided into lineages that would eventually give rise to the Taymyr wolf, modern gray wolves, and today’s dogs.
“It looks like a three-way split that all happened around the same time,” says lead author Pontus Skoglund, a postdoc at Harvard University. According to the genetic mutation rate the researchers calculated by comparing the DNA of the Taymyr wolf with that of dogs and other wolves, the lineage that gave rise to today’s dogs arose somewhere between 27,000 and 40,000 years ago, the team reports online today in Current Biology.
“I like that time period,” says Wayne, whose own work indicates that dogs arose in Europe about this time. “That’s when modern humans first entered Europe and began encountering wolves that became the raw material for dogs,” he says, referring to the older end of the time frame. “It’s a good paper,” agrees Peter Savolainen, a geneticist at the Royal Institute of Technology in Stockholm, who was not involved with the work. His team’s analysis of modern dog and wolf DNA suggests that the wolf and dog lineages split off from each other about 32,000 years ago. “It’s really nice that the modern and ancient DNA matches up,” he says.
Still, neither Savolainen nor Wayne—who have argued over whether dogs arose in Asia or Europe—thinks the study provides clarity on that debate or whether dogs were domesticated multiple times, as some scientists have proposed. “There’s still a lot of open questions,” Skoglund agrees.
Also unclear is whether Siberian huskies and Greenland sledge dogs—both considered ancient breeds—were among the first types of dogs. When Skoglund, Dalén, and their colleagues compared the DNA of the Taymyr wolf with that of 48 dog breeds, they found that Greenland sledge dogs and Siberian huskies shared more ancestry with the Taymyr wolf than did any other breed. That could mean that these two breeds arose soon after dogs split from wolves. But it could also be a genetic red herring, especially if these breeds mated with descendants of the Taymyr wolf in recent history. Still, Dalén says, “my hunch is that both are a fairly early form of dog.”