What is the origin of dogs? When did the wolf, an animal not known for its affection for humans, transform into man's best friend?
Prior research found that dogs diverged from wolves after the last Ice Age, no earlier than 16,000 years ago. But now, a study released in the June issue of Current Biology finds that the fabled relationship between humans and canines may be much older than we previously believed.
Pontus Skoglund from the Department of Genetics at Harvard University, along with biologist Erik Ersmark, Eleftheria Palkopoulou, and Love Dalén from Stockholm University analyzed a rib of a canine discovered in Russia's Taimyr Peninsula in 2010. The bone's genome revealed that it belong to an ancient wolf, one that was equally related to both modern gray wolves and dogs.
Carbon dating revealed that this Taimyr wolf lived about 35,000 years ago.
Using genetic sequencing, the researchers then concluded that the split between wolves and dogs occurred between 27,000 and 40,000 years ago, about three times earlier than everyone had thought.
"Dogs may have been domesticated much earlier than is generally believed," said Dr. Dalén of the Swedish Museum of Natural History and Stockholm University. “It is interesting that this [finding] suggests that domestication happened before the development of agriculture.”
Humans are thought to have begun farming about 12,000 years ago.
The research team analyzed mitochondrial DNA using shotgun sequencing, a method for identifying the building blocks of long strands of DNA, to discover that the Taimyr wolf was symmetrically related to both gray wolves and dogs. They concluded they had discovered an ancient ancestor to the dog.
But when analyzing the genome according to traditionally accepted rates of mutation, the authors were unable to explain how the bone fragment they discovered could date so far back. They concluded either a slower mutation rate or a longer generation time was necessary to explain this phenomenon. Or perhaps both.
“The most significant finding is the recalibration of the [rate of mutation] time scale,” said Dr. Skoglund, “and that opens up the possibility of an earlier domestication.”
“We think the simplest explanation for our results is that dogs were domesticated earlier than other studies have suggested,” added Dalén.
Dog-genome expert Peter Savolainen of the Royal Institute of Technology (KTH) in Stockholm, Sweden, who did not participate in this study, cautions against concluding that the age of a specimen indicates the date of domestication.
“We cannot be sure that this split was when the dogs were actually domesticated.” Skoglund agreed, “We wouldn’t know if [the wolf] was tame or wild just by looking at this information.”
But despite questioning some of the researchers’ conclusions, Dr. Savolainen agrees that this new study contributes a “really good molecular clock” to the field. Savolainen’s own research on the origins of dogs in Madagascar appears this week.
If it's true that Fido predates farming, what does that say about human nature?
“This kind of highlights the resourcefulness of early humans; they were resourceful enough to domesticate the dog,” said Dalén. “It says something about how humans interact with the world around them,” added Skoglund.