Analysis of genetic markers in blood samples taken from dogs in 38 countries across six continents suggests dogs were first domesticated in Central Asia, somewhere near India or Nepal, a new study says.

The DNA of thousands of dogs collected over seven years was analyzed in an attempt to determine the ancestry and geographical origin of today's domesticated dogs, the researchers say.

"This is the first global study of genomic patterns of dog diversity," study leader Adam Boyko of Cornell University in Ithaca, New York, says. "We find a clear pattern of genetic diversity focused on central Asia, suggesting the first domesticated dogs came from this region."

The research team collected DNA samples taken from so-called "village dogs" that live near human settlements but can be feral, strays, and simply hanging around but not belonging to any particular person.

Village dogs are a better source of an authentic genetic signature of original dog populations than modern-day purebred dogs, whose genetic line only goes back 200 years or so, the researchers say.

"They are very different from pure-bred dogs genetically because they are free-breeding, so in a genetic sense, they are a natural population," Boyko says.

The new study is just the latest to tackle the long-running debate about when and where wild wolves first began to be domesticated to become man's best friend.

Previous studies have proposed origins in Europe, Siberia, the Middle East and southern China.

Boyko acknowledges his study by itself is not likely to end the debate.

"I'm not pretending my study alone is enough to rally the community together," he says.

Another expert, Greger Larson from the University of Oxford, said Boyko's study was a "major step forward" but questioned whether using DNA from modern-day dogs can reveal the true origins of dogs.

He notes that almost every geographical region on Earth has at least one study presenting it as a candidate for the domestication of dogs.

"Adding Central Asia now means that everyone with a favorite region can point to at least one paper that supports their suspicions," he says.

Although Boyko's study points to Central Asian for the rise of domesticated dogs, it made no attempt to put a timeline on the event.

One previous genome study of living dogs and wolves proposed the domestication happened around 10,000 years ago, when wolves scavenging at the fringes of human settlements gradually became more and more accustomed to living in close proximity to people.

Other studies have suggested domestication took place in East Asia about 32,000 years ago, while another proposed Europe and a timeline between 32,000 and 18,000 years ago.

And the debate continues.