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.