(Image: Iztok Noc/Getty)

Man’s best friend may be a very old friend indeed. An analysis of a bone from a newly identified ancient wolf species suggests dogs may have split from wolves as early as 40,000 years ago – with or without being domesticated at the same time.

Exactly when dogs started to be domesticated and split from wolves is a matter of some controversy. Archaeological evidence analysing the shapes of canid skulls found near early human camps suggested it might have happened as far back as 35,000 years ago. DNA analysis, focusing on differences between living dog and wolf genomes, seemed to suggest they must have split much more recently – between 11,000 and 16,000 years ago.

Now Love Dalén from the Swedish Museum of Natural History in Stockholm and colleagues have sequenced the genome of a wolf that lived 35,000 years ago in Taimyr, northern Russia, according to carbon dating. This allowed them to recalibrate the molecular clock – the rate at which genetic differences accumulate over time – and better reconstruct the wolf-dog evolutionary tree.

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They found that dogs and wolves must have split into two separate lineages 27,000 to 40,000 years ago, bringing the DNA and archaeological evidence into line with each other.

They also found that some northern latitude dog breeds, having split from wolves, then interbred with the now extinct Taimyr wolf, which could have helped them adapt to the challenging northern environment. These breeds include the husky, Greenland sledge dog and, to a lesser extent, the Chinese shar pei and Finnish spitz.

But although the findings back an early split of dogs from wolves, they don’t tell us when the domestication of dogs started. “The present study does not rule out the possibility of a very early date indeed, but it does not rule the possibility of a much later date either,” says Laurent Frantz from the University of Oxford.

Perhaps humans didn’t domesticate dogs once the creatures had split away from wolves: the alternative possibility is that there was an early split between two types of wolves, and that dogs emerged much later on one of these lineages. “We do not yet know whether it infers an early divergence between two wolf populations or between wolves and dogs,” says Frantz.

Dalén says a combination of genomic and morphological work on ancient wolf or dog specimens is needed before we have a conclusive date on the time of domestication.

Mietje Germonpre of the Royal Belgian Institute of Natural Sciences in Brussels was one of the researchers who did the skull-shape work that suggested an early date of domestication. She is excited by the new findings, and says she is already studying a lot more specimens that should help clarify the question.

“I find it interesting that early modern humans might have been so resourceful that they started making use of dogs already during the height of the last Ice Age,” says Dalén.

Journal reference: Current Biology, DOI: 10.1016/j.cub.2015.04.019