Man's best friend has been the dog for a long time, but where and when did the camaraderie begin? Swedish, Chinese, and U.S. researchers have an answer based on genetic analysis of dogs and wolves from all over the world.
Two studies in the journal Science indicate that domesticated dogs first appeared somewhere in East Asia, spread across Asia and Europe, and then followed their two-legged companions into the New World 12,000 to 14,000 years ago.
One study by a Swedish and Chinese team suggests humans may have domesticated dogs from wolves as recently as 15,000 years ago. Team leader Peter Savolainen of the Royal Institute of Technology in Stockholm says an analysis of DNA from over 600 dogs worldwide and nearly 40 Eurasian wolves shows that dogs share a common gene pool and one geographic origin.
"We found that there was much more genetic variation in the samples in East Asia than in the other parts of the world," Mr. Savolainen said. "This tells us that the geographic origin must have been east Asia."
While the researchers cannot pinpoint the specific location, they say China would be a good guess.
Previous researchers had looked to the Middle East as the site for both animal and plant domestication.
The domestication date is less certain. The Swedish and Chinese scientists say if dogs evolved from just one wolf ancestor, the domestication time would be about 40,000 years ago. However, their analysis and previous ones indicate lineages from at least four and possibly six wolves, suggesting a more recent origin. That is because the more sources of domestication, the less time it takes to develop the genetic variation seen today in dogs.
"Looking just at our data, we think 15,000 years seems most probable," Team leader Peter Savolainen said. "Apart from that, also the archaeological data suggest an origin about 15,000 years ago. So altogether, it's kind of a good majority for this 15,000 years."
A second research team from several U.S. institutions supports the notion of the single originating locale for dogs. They studied whether dogs in the New World were domesticated independently from Old World dogs, or whether the two groups were related. They compared the genetic sequences of the two groups, including some Latin American and Alaskan animals that predated the arrival of European explorers in the 15th century.
Again, the similarities indicate that all the dogs shared a common ancestor. That suggests that they arrived in the Americas with the hunter-gatherers who crossed the Bering Strait from Asia 12,000 to 14,000 years ago.
A certain cluster of gene material from ancient Latin American dogs did not match any from modern dogs. This indicates that European colonists probably did not use native American dogs to create the breeds known today, but instead brought their own.