Where Did Dogs Become Our "Best Friends"?

August 3, 2009

DNA from scrappy dogs in African villages is raising doubts about a theory that dogs first became "man's best friend" in East Asia.

Based on DNA evidence, scientists believe that domestic dogs originated from Eurasian gray wolves sometime between 15,000 and 40,000 years ago.

(Related: "Dog Genome Mapped, Shows Similarities to Humans.")

The history of how dogs became human companions, however, remains muddy.

In 2002 researchers had examined DNA from hundreds of dogs around the world and found that East Asian dogs are the most genetically diverse.

Since the highest diversity should exist in the region where dogs first went from wolf to woof, the study seemed to suggest that the dog-human bond was forged in East Asia.

That study included almost equal numbers of East Asian "breed" dogs and "village" dogs, said study co-author Adam Boyko, a biologist at Cornell University in Ithaca, New York.

Breed dogs include purebred and mixed-breed animals. Village dogs are those that are indigenous to a specific region and "were not subject to the same degree of intense artificial selection and closed breeding practices that characterize modern breed dogs," the study authors write.

Equally Diverse

For the new survey, Boyko and colleagues examined DNA from village and breed dogs living across Africa, plus Puerto Rican street dogs and mixed-breed dogs in the U.S.

The team found that the African village dogs' genetic diversity matches that of East Asian village dogs.

The authors note that this does not mean domestic dogs might have originated in Africa.

"We know Africa cannot be where dogs were domesticated, because there are no gray wolves there," Boyko said. But the findings call into question the previous proof that dogs were first domesticated in East Asia.

"What we think we are picking up on is actually the signal of village dogs have more genetic diversity than breed dogs do, … ," he said.

That's not to say East Asia is out of the running. But to definitively solve the riddle, scientists should obtain genetic samples from village dogs throughout Europe, the Middle East, and East Asia, Boyko said.

Once the timing and location of domestication is resolved, he added, doggie DNA could help unravel mysteries about early human-migration patterns and population histories.

For example, he noted, "there's pretty good evidence that they followed humans into the New World, and they certainly followed along the Polynesians in their exploring."

Findings appear this week in the Proceedings of the National Academy of Sciences.




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