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15,000 years with man's best friend

Tight bond between dogs, masters unleash research surprises

By Marsha Walton

DNA analysis of dogs now found in most of the world showed the most genetic diversity in East Asia, meaning dogs have likely been domesticated there the longest.
DNA analysis of dogs showed the most genetic diversity in East Asia, meaning canines likely have been domesticated there the longest.

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(CNN) -- About 15,000 years of friendship between man and dog have helped man's best friend to develop unique ways of understanding humans: abilities that still are somewhat mysterious to scientists and dog lovers, several studies released this week found.

Whether it's a beagle, basenji or basset hound, scientists say dogs all over the globe descended from one common ancestor, probably somewhere in East Asia about 15,000 years ago, and they have followed man through his migrations over the Earth.

"Dogs are an important part of our human history, and until now there hasn't been much common knowledge, only a lot of common guessing about their origin," said Peter Savolainen, a geneticist at the Royal Institute of Technology in Stockholm, Sweden.

Tracing the origins

Three studies in this week's Science magazine provide evidence that early humans had domesticated gray wolves by the time they crossed the Bering Strait to settle the New World, 12,000 to 14,000 years ago. DNA analysis of dogs worldwide showed the most genetic diversity in East Asia, meaning dogs have likely been domesticated there the longest. Another study that compared Old and New World dogs found that canines in North and South America also descended from that same Eurasian mother.

"We know that dogs were useful for lots of things in Stone Age culture, as draft animals, in hunting, for warmth, and for protection," said Jennifer Leonard, a postdoctoral fellow at the Smithsonian Institution's National Museum of Natural History.

And in sharing food, shelter, survival and play, modern dogs have somehow genetically acquired an insight about humans that has earned them the title of man's best friend.

"It looks like dogs really do understand what we are trying to tell them, they are thinking about what we want, and they understand that we are trying to communicate," said Brian Hare of Harvard University, who authored one of the studies.

Picking up on human needs

Not only did the dogs Hare tested pick up on what human researchers were trying to convey, they surprised scientists by doing it much better than other species, even chimpanzees.

Hare's experiment worked in the following manner: A researcher stood near two containers, one of which had food inside. Testing dogs, puppies, wolves and chimpanzees, the researcher would send some cue, either by looking at, tapping on or putting some mark on the food container.

The adult dogs and puppies picked the correct container far more often than either the chimps or the wolves did, and far more often than chance levels. (Controls ruled out the possibility that the animals smelled the food.) By doing so, the dogs defied the expectations of a lot of scientists.

"Wolves have bigger brains than dogs, so it was thought the wolves would do better," Hare said. "And chimpanzees are primates, closer to humans, so it was thought they would do better."

Even the theory that the adult dogs would outperform the puppies because they had spent more time with humans was quashed, when puppies as young as 9 weeks old successfully picked up on subtle cues from human researchers.

"Dogs have a talent for reading social cues in a very sophisticated way," Hare said.

It's in the genes?

These results are not so surprising to zoology professor and dog behavior expert Patricia McConnell.

"Domestic dogs follow humans like a laser and watch the behavior of their humans with a focus that is astounding," said McConnell, a professor at the University of Wisconsin in Madison. "This opens up big and interesting questions about how social intelligence is passed on genetically."

But McConnell said what's not yet understood is which of the cues that humans give are the ones the dog picks out as relevant.

"Perhaps you've taught your dog to sit, and you want to show this off to your friends," McConnell said. "You say, 'Sit,' but he just looks at you."

The rise of designer dogs

The dog, she said, might have learned to sit -- not by your words but by how your head was turned or what your body language was like when he was learning. If those things are different in a roomful of people, the command "sit" may not do the trick.

These visual cues can be critical, said McConnell, who often works with aggressive dogs. A difference of a quarter inch in a human's head movement can be the difference between a calm dog and one that attacks.

But with one common ancestor, why the vast differences in size, shape and skills between shepherds and Shih Tzus, bull mastiffs and border collies?

That's all the work of humans, not genetics. People started creating designer dogs about 500 years ago, said Savolainen, the geneticist at the Royal Institute of Technology.

Upper classes started breeding better hunting and herding dogs and cuter lap dogs. The American Kennel Club now recognizes 150 breeds.

And they're all keeping a watchful eye over their humans.

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