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Who Let the Dogs In? And When?
New Studies Ponder Origins of Pets' Domestication

By Rick Weiss
Washington Post Staff Writer
Friday, November 22, 2002; Page A01

Research has long indicated that all dogs, from prissy Pekingese to slobbering St. Bernards, are the domesticated descendants of wolves. But scientists have tussled for years over when and where the transition from wild carnivore to newspaper-toting pet began -- and why, exactly, dogs and humans have gotten along so well.

Now a new analysis of dog DNA pegs East Asia as the place where wolves and people began their dance of domestication -- not Europe or the Middle East, as some experts have contended. The work also suggests that domestication occurred much more recently than had been thought, and that dogs dispersed with surprising speed into new territories with humans -- evidence, perhaps, of their great popularity and utility.

The new findings rewrite the story of how dogs made their remarkable evolutionary journey from wilderness wanderers to their place today in tens of millions of cozy American households. It's a story that scientists concede is still far from finished and will need to be revamped as additional research gets done.

Meanwhile, a study being published simultaneously today helps explain what may be the most enduring canine mystery of all: What is it about dogs that makes them so compatible with people? In the first direct comparison of its kind between dogs and chimpanzees, dogs demonstrated an uncanny ability to interpret human communicative cues -- gleaning information from subtle hand gestures and even getting the meaning of a human glance -- while the brainy chimps remained clueless to what was going on.

It may not be news to dog owners, but now it can be said with some scientific assurance: Centuries of selective breeding has created an animal that in some respects, at least, understands us even better than our closest primate cousins.

"It looks like there's been direct selection for dogs with the ability to read social cues in humans," said Brian Hare, a Harvard biological anthropologist who led the behavior study.

Scientists suspect that wolves hung around primitive human hunter-gatherers long before the first wolf was domesticated, perhaps in the hope of stealing scraps of food. Eventually, the theory goes, humans cajoled a few to help with hunting or guarding, and began breeding those that proved to be the best companions.

Domestication, of course, is a matter of perspective. Some experts suspect that a few clever wolves initiated the process, recognizing that free food and a warm home beats living in the wild. Either way, scientists would like to know when and where it happened. But that has proven difficult.

Bones from small, doglike animals have been found in human sites dating back 100,000 years or more, but specimens older than about 10,000 years are difficult to identify accurately, said Peter Savolainen of the Royal Institute of Technology in Sweden, who led one of three dog studies appearing in today's issue of the journal Science. "You can't say for sure whether they're from dogs or small wolves."

So Savolainen went with a more modern approach. He and his colleagues counted the number of mutations within a stretch of genetic material known as mitochondrial DNA in 654 dogs from Europe, Asia, Africa and Arctic America, and also in wolves. This is the largest such study ever conducted.

Based on the widely accepted assumption that such mutations occur about every 20,000 years, the researchers calculated that domestic dog DNA first appeared about 15,000 years ago -- or perhaps 40,000 years ago in the less likely event that domestication started with just one wolf rather than several.

That's much more recent than the 100,000 years ago that scientists had concluded from a smaller DNA study published in 1997. The difference is significant, because dogs were clearly widespread around the world about 9,000 years ago, and such a rapid dispersal over a few thousand years would suggest dogs were valuable to migrating people and were perhaps widely traded.

Still, some researchers said they don't trust the new numbers, in part because such calculations are inherently dependent on so many assumptions. "I think it's still an open question," said Robert K. Wayne, the University of California at Los Angeles, evolutionary biologist who oversaw the older study.

Savolainen's group also found that dogs from East Asia had the highest level of DNA variability, suggesting that domestication originated around there -- probably in eastern China or perhaps Japan. But this finding, too, faces challenges. Italian researchers have recently gathered evidence pointing to Italy as being home to the world's first dogs. Other scientists have said they stand by their claim that dogs first appeared in the Middle East -- perhaps in Israel or Iraq, where the first agricultural settlements emerged.

Whenever it happened, it was long before most of today's familiar breeds came into being. The vast majority of today's 400-plus breeds -- about 150 of them formally recognized by kennel associations -- did not appear until intensive breeding came into a vogue a few hundred years ago. Still, all those breeds can trace their ancestry to a handful of wolves that began living with people thousands of years ago.

In a second study, scientists present DNA evidence that even New World dogs are the offspring of East Asian wolves and are not the descendants of native American wolves. The first dogs in the New World apparently came along as newly domesticated companions when humans migrated from Asia to North America 12,000 to 14,000 years ago.

"That tells us that dogs were very important," perhaps as sled dogs, food protectors, hunters or even as food sources themselves, said Jennifer A. Leonard, now at the Smithsonian's National Museum of Natural History, who helped lead the study. "Remember, these are hunter-gatherers in the Stone Age. They don't have a lot of stuff, and dogs have to be fed and, to some extent, taken care of."

In a third report, researchers describe several experiments aimed at unveiling the biological and behavioral essence of the human-dog relationship. One experiment presented dogs and chimps with two smell-proof boxes, one empty and the other containing a treat. The team tested the animals' ability to read hints from a person as to which box had the food -- hints such as tapping on the box or even pointing at the food box and gazing at it.

The dogs, represented by several breeds, usually picked up on the signals and chose the right box, while chimps performed no better than chance. Hare, the Harvard doctoral candidate who designed the study after trying the test on his own two dogs, acknowledged that chimps perform better than dogs on many kinds of tests. "But in this simple task involving . . . communicative signaling with humans, chimpanzees fall flat on their faces," he said.

In a separate series of experiments comparing test performance among human-raised puppies, kennel-raised puppies, dogs and wolves, Hare and his colleagues concluded that this communicative talent is not learned from human interaction during puppyhood and is lacking in wolves. That suggests it has become an innate trait among dogs -- the result of individual dogs' having been selected and bred over hundreds or thousands of years on the basis of their ability to "understand" their masters.

Raymond Coppinger, a professor of biology and dog expert at Hampshire College in Amherst, Mass., called the experiments a good start at understanding the dog mind, but emphasized that such experiments are difficult to design well.

"This argument about cognition and who has it has been going on since Aristotle," Coppinger said. "The thought that one article is going to answer it now for dogs is, well, you fill in the ending."

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