New DNA evidence from a wolf bone suggests humans and dogs were companions for much longer than previously thought.

Modern Siberian huskies and Greenland dogs turn out to share an unusually large number of genes with a wolf that lived 35,000 years ago -- a time when our species was just beginning to populate Europe and Asia, reports the Current Biology study.

This animal, the Taimyr wolf of Siberia, is the most recent common ancestor of modern wolves and dogs.

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"We find that the ancestors of domestic dogs must have separated from the ancestors of wolves at least 27,000 years ago," lead author Pontus Skoglund, a Harvard University geneticist, told Discovery News.

"As for the genetic link between the 35,000-year-old wolf and Husky-type dogs, the most natural explanation is that these dog breeds absorbed local wolf ancestry that still lived on in Siberia when they followed early human groups to this region," he said. "This is the first direct evidence we have that the diversity in common dog breeds today has such deep roots."

It's likely that many other dog breeds today are also related to prehistoric regional gray wolf populations, helping to explain why there is such incredible diversity among dogs, from Golden retrievers to poodles, due to factors beyond humans selecting for certain traits.

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Skoglund and his colleagues made the discoveries after analyzing a small bone picked up during an expedition to the Taimyr Peninsula in Siberia. DNA tests revealed that the bone belonged to the prehistoric Taimyr wolf.

The direct dating of the wolf bone, combined with further genetic analysis, enabled the researchers to recalibrate the molecular timescale of wolves and dogs. This found that the mutation rate between the two is substantially slower than assumed by most prior studies, suggesting that the ancestors of dogs were separated from present-day wolves around 27,000 years ago.

Senior author Love Dalén of the Swedish Museum of Natural History told Discovery News that some of the debate over when dogs were "domesticated" hinges on the precise meaning of that word. If it is taken to mean a fully tame dog that doesn't look much like a wolf, then that happened much later.

"But if 'being domesticated' means an animal population that is held and breeds in captivity, then our results are consistent with dogs being domesticated at least 27,000 years ago," Dalén said.

Siberian husky at Yosemite National Park. Wikimedia Commons

Based on the new findings, the researchers propose that this kind of domestication happened just once, and probably from "a population of wolf that roamed the tundra steppe of the last Ice Age," Dalén shared.

As for what triggered the event, he and her colleagues suspect that "dogs may have originated through capture of wolf cubs or through self-domestication via attraction to food scraps," such as the meat and bones left behind by hunter-gatherers.

This is significant, because other research groups have tied dog domestication to farming, when humans first settled down to grow crops. That happened long after 27,000 years ago, however, so Skoglund and his team do not think farming led to dog domestication.

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After domestication occurred, the researchers believe that as the wolf-resembling dogs traveled with humans, they interbred with multiple regional wolf populations, such as the one for the Taimyr wolf in Siberia.

Greger Larson, director of the Palaeogenomics & Bio-Archaeology Research Network at the University of Oxford, told Discovery News that the new study "is a significant step forward in the long winding road toward a satisfying understanding of how, when and where dogs were domesticated."

Larson said that the two major findings of the new paper are the recalibration of the molecular rate of evolution between dogs and wolves, and the demonstration that some modern dog breeds may share genes with certain early regional wolves.

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This "suggests," he said, "that regardless of where dogs were domesticated, they often acquired a portion of their genomes from local wolf populations. This has been suspected, but never quite demonstrated like this."

In terms of precisely when and where the very first dogs emerged, he said that it's too early to close the book on the still heated debate.