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Man's Best—and Oldest—Friend

New research opens up the possibility that the bond between humans and dogs is much older than previously thought.
(Photo: Brian Talbot/Flickr)

(Photo: Brian Talbot/Flickr)

Dogs may have become man’s best friend much earlier than previously thought, according to research published today in the journal Current Biology.

A new study finds that dogs' ancestors may have split from wolves as much as 40,000 years ago. This comes in direct contrast to previous genetic analyses, which suggested that the split occurred just 16,000 years ago, according to Pontus Skoglund, a research fellow in genetics at Harvard Medical School, and lead author on the study.

Researchers still don’t know exactly when or where dogs were domesticated, or even which wolf population eventually gave way to our obedient sidekicks. So when Skoglund and his colleagues at Stockholm University and the Swedish Museum of Natural History came across an ancient Siberian wolf bone, they hoped “this ancient wolf might shed some light on that question,” Skoglund says.

If the ancient wolf was roaming Siberia 35,000 years ago, the ancestor to modern dogs might have been as well.

The wolf rib was collected from the Russian Taimyr Peninsula in 2010, and radiocarbon dating revealed that the bone was roughly 35,000 years old. The team sequenced the Taimyr wolf’s genome and built population history models based on the genetic data of the ancient wolf and that of modern-day wolves and dogs. By comparing the genomes, they found that all three lineages likely split from a common ancestor around the same time. And if the ancient wolf was roaming Siberia 35,000 years ago, the authors reasoned, the ancestor to modern dogs might have been as well.

The team found more evidence for this theory by determining the mutation rate for dogs—the amount of time it would take for all the genetic differences between modern-day wolves and dogs to arise. They then compared the ancient wolf’s genome to modern day populations’, and found that the mutation rate had to be half as fast as the previous estimates, which the authors say were based on assumptions rather than direct measures. In other words, the genetic changes that made dogs distinct from wolves arose much more slowly than previously thought; the differences between wolves and dogs today would need about twice as long as the estimated 16,000 years to develop. The authors conclude that the ancestors to dogs likely split from modern-day wolves’ ancestor between 27,000 and 40,000 years ago.

This research opens up the possibility that dogs were domesticated much earlier than previously thought, although we still don’t know exactly when dogs became humanity's best friend. “We can’t tell for sure just from the genetics,” says Skoglund, who adds that the most exciting finding is that Husky-type dog breeds share approximately 3.5 percent of their DNA with the Taimyr wolf.  The genetic link suggests the dogs' ancestors interbred with the ancient wolf population at some point in the past.

Skoglund, who spends most of his time working on ancient human genomes, sees parallels to our own history, and the link we share with another extinct species: “This ancient wolf is to Siberian Huskies what Neanderthals are to people outside of Africa,” he says.

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