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A dog in wolf’s clothing

ALL DOMESTIC dogs are descended from just a few wolves tamed in East Asia about 15,000 years ago, according to the first research to trace the animal’s genetic origins.

Breeds of all shapes and sizes, and from every continent, share common ancestors that were domesticated by early humans in China or Mongolia, a comprehensive analysis of the canine gene pool says.

Once tamed, probably to help with hunting, dogs spread rapidly around the world, travelling with Asian tribes as they migrated through Europe, Asia and Africa, and across the Bering Strait into the Americas.

The animals proved so useful to mankind that it may have taken as little as 1,000 years for them to reach every continent. The differing size and shape of modern breeds, from Dobermann to Dachshund, has emerged only in the past 500 years, as a result of breeding programmes.

Canis familiaris, the domestic dog, is well known to have evolved from the grey wolf, Canis lupus, but the pattern of when and where the wolf was tamed has been obscure. As wolves were once abundant in Eurasia, Africa and North America, the first dogs could have been tamed either by a single tribe, or bred independently from local wolves in many regions.

Two genetic studies by Swedish, American and Chinese scientists now show that the domestic dog had a single origin in East Asia, from which it followed its masters as they travelled the world.

In the first study, a team led by Peter Savolainen of the Royal Institute of Technology in Stockholm analysed the DNA of 654 dogs, representing all the world’s major breeds and populations, seeking the site and date of the first genetic split from wolves.

The results, published today in the journal Science, show that the first dogs emerged between 40,000 and 15,000 years ago. Dr Savolainen said that an origin 15,000 years ago was most likely as the oldest dog fossil, found in Germany, was 14,000 years old.

Genetic diversity was highest among modern dogs in East Asia, indicating strongly that dogs have been domesticated in the region for the longest time. Increased genetic variety is a good indicator of age, as it grows with every generation of a species.

No similarity

Modern wolves living in East Asia include the tundra wolf, Canis lupus albus; the Tibetan wolf, Canis lupus laniger; and the Indian wolf, Canis lupus pallipes. Modern dogs could have emerged from one of these subspecies, or from another type of wolf that has since become extinct.

The second study, led by Carles Vilà of Uppsala University in Sweden, compared the DNA sequences of dogs from the Old and New Worlds, including the remains of animals that lived before the voyage of Columbus, to determine whether the animals had been domesticated independently from American wolves.

His team found no similarities between wild American species and domestic dogs on the continent, both before and after the arrival of the Europeans in the 15th and 16th centuries.

This shows that dogs were already a tame, separate species when they were introduced to the continent, and share the same ancestry as their European and Asian cousins. Even American breeds such as the Newfoundland, the Alaskan husky and the Chesapeake Bay retriever, are really Asian in origin.

The evidence suggests that, just as early humans evolved in Africa and spread through the world rather than evolving separately in many regions, so dogs were first tamed in East Asia then followed mankind globally. Even Australasian dogs, such as the dingo and the New Guinea singing dog, share the same origin.

The genetic data overturn conventional ideas about the domestication of dogs, which is often thought to have begun in the Middle East, possibly in the Fertile Crescent of modern Iraq, where farming and livestock originated.

Dr Savolainen said: "Most earlier guesses have focused on the Middle East as the place of origin for dogs, based on few known facts: a small amount of archaeological evidence from the region, and the fact that several other animals were domesticated there.

"A synthesis of available data points to an origin of the domestic dog in East Asia, approximately 15,000 years before present."

Dr Vilà said that it was clear that the spread of dogs mirrored patterns of human migration. "We found that dogs originating in the Old World arrived to the New World with immigrating humans," he said. "Thus, even before the development of trade as we know it now, humans had to be exchanging dogs."

The reason for the domestication of dogs, and their success in human communities, remains unknown, but many researchers believe that their role in hunting was crucial.

"I can imagine that if dogs were, for example, improving the quality of hunting that would be a very great advantage for humans," Dr Vilà said.

"There must have been something extremely advantageous about those dogs that made them extremely successful and allowed them to spread around the world."

Intelligent

Major differences in size, shape and temperament between breeds of dog is a recent phenomenon, the genetic studies suggest. About 500 years of selective breeding programmes, in which dogs are chosen for size, speed, aggression or docility, are responsible for the distinctions between a Pekingese and a pit bull terrier, not a different genetic origin.

Dr Savolainen said that although dogs would always have varied in size extreme variations between breeds began to develop only from medieval times. "The medieval upper classes wanted dogs for specific purposes, such as hunting or for lapdogs and so on, and they selectively bred animals with those qualities," he said. "You English have done a lot in the last 200 years to achieve this."

A third study, led by Brian Hare of Harvard University in Cambridge, Massachusetts, suggests that the close interaction between man and his best friend has made dogs more intelligent animals, and helped humans to survive as hunter-gatherers.

Dogs are much better than wolves or chimpanzees at finding food hidden in one of two containers, on the basis of social clues given by humans, the research found.