The dog has long been considered man's best friend. Now new findings may explain just when humans first domesticated their furry friends. According to reports published today in the journal Science, today's dogs originated from East Asian wolves about 15,000 years ago.

Previous research had established the wolf as the ancestor of today's dog, but when and where humans first domesticated the animals remained unclear. Peter Savolainen of the Royal Institute of Technology in Stockholm and his colleagues examined samples of mitochondrial DNA (which is passed solely through the mother) from 654 dogs representing all major dog populations worldwide. More than 95 percent of the dogs belonged to just three major groups, the team found. What is more, the distribution among these groups was similar across all regions, which suggests "a common origin from a single gene pool for all dog populations," the authors write. Because the East Asian group displayed the greatest genetic diversity, the scientists posit that dogs were domesticated there first. Prior work had suggested that domesticated dogs came from the Middle East based on archaeological evidence and domestication patterns for other animals.

The results of a second study suggest that soon after domestication dogs began accompanying humans on long journeys. Jennifer A. Leonard of the Smithsonian Institution and her colleagues investigated the origins of dogs in the New World to try to determine whether they arose independently from wolves in the area or if they were tied to their Old World counterparts. The scientists extracted DNA from 37 dogs specimens recovered from archaeological sites in Mexico, Peru and Boliva that predated Columbus's arrival. In addition, the team analyzed DNA from the remains of dogs found in Alaska that date from before the arrival of European explorers. The researchers found similarities in the genetic sequences that suggest that "ancient American and Eurasian domestic dogs share a common origin from Old World gray wolves." The explorers that crossed the Bering Strait between 12,00 and 14,000 years ago most likely brought a number of different lineages of dogs with them, they conclude. "I can imagine that if dogs were, for example, improving the quality of hunting, that would be a very great advantage for humans," says study co-author Carles Vilà of Uppsala University in Sweden. "It could have even made the colonization of the New World easier."