Dogs have been man's best friend even before humans began to settle down and started farming, but scientists have not been certain where the animals were first domesticated.

A 2015 study that involved looking at blood samples of dogs from 38 countries suggests that the domestication of dogs occurred in Central Asia somewhere near Nepal or India, but there are also other studies that suggest humans first domesticated wolves in Europe, Middle East, Siberia and China.

Now, a new genetic study of hundreds of canines could help explain the discrepancies in the results of these studies as it has found evidence suggesting that dogs may have been domesticated not just once but on at least two occasions in two different parts of the world.

For their research published in the journal Science on June 3, Greger Larson, from Oxford University, and colleagues looked at the genetic data of 59 ancient dogs and a 4,800-year-old dog fossil discovered in Newgrange, an archeological site in Ireland, then compared these with those of more than 2,500 modern dogs.

The researchers found a deep split between the dog populations that currently live in East Asia and Europe, suggesting that dogs were separately domesticated both in Europe and Asia but eventually mixed as humans migrated to Western Europe and the Middle East.

Over time, a dramatic population turnover event occurred in Europe, which replaced the earliest population of domesticated dogs that lived there.

"Our analyses revealed a deep split separating modern East Asian and Western Eurasian dogs," the researchers wrote in their study.

"These results suggest that dogs may have been domesticated independently in Eastern and Western Eurasia from distinct wolf populations. East Eurasian dogs were then possibly transported to Europe with people, where they partially replaced European Paleolithic dogs."

The findings could mean that most modern dogs are a genetic mix of the European and Asian ancestors and could partly explain why earlier genetic studies that attempt to pinpoint the birthplace of canine domestication have been difficult to interpret.

"We need to reconsider the number of times dogs were domesticated independently," Larson said. "Maybe the reason there hasn't yet been a consensus about where dogs were domesticated is because everyone has been a little bit right."

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