By Rick Weiss
Washington Post Staff Writer
Thursday, November 21, 2002; 4:05 PM
Research has long indicated that all dogs, from prissy Pekingese to slobbering St. Bernards, are the domesticated descendants of wolves. But scientists have tussled like puppies over the question of 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 co-domestication -- not Europe or the Middle East, as some experts have contended. The work also suggests that domestication began about 15,000 years ago, much more recently than some had previously concluded.
But it's an accompanying study, also being published today, that has dog-lovers really panting. 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 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 human hunter gatherers long before the first one 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. But while scientists may never know the motivations behind domestication, they have doggedly pursued its timing and location.
Bones from small, dog-like animals have been found in human archaeological sites dating back 100,000 years or more, but specimens older than about 10,000 years old 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."
Savolainen's team counted the number of mutations within a particular stretch of so-called mitochondrial DNA in 654 dogs from Europe, Asia, Africa and Arctic America -- the largest such study ever conducted. Working with the common but not universally held understanding that such mutations occur about every 20,000 years, they calculated that domestic dog DNA first appeared about 15,000 years ago -- and perhaps 40,000 years ago in the less likely event that domestication started with just one or a few wolves rather than many.
That's much more recent than the 100,000 years ago that scientists had concluded from a smaller DNA study published five years ago. The difference is significant because dogs were clearly widespread around the world not much later, and such a rapid dispersal would be added evidence of their popularity and utility.
But some researchers said they don't trust the new numbers, in part because such calculations are inherently dependent on so many iffy assumptions. "I think it's still an open question," said Robert K. Wayne, the University of California, Los Angeles, evolutionary biologist who oversaw the older study that suggested a more distant date.
Savolainen's group also found that dogs from East Asia had the highest level of DNA variability, suggesting that canid 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. And other scientists have said they stand by their claim that dogs first appeared in the Middle East -- perhaps in Israel or Iraq, in conjunction with the first agricultural settlements.
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 come into being until intensive breeding came into a vogue a few hundred 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 about 12,000 to 14,000 years ago.
"That tells us that dogs were very important," 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."
No one knows what role dogs played so early in their domestication, Leonard said, but it may have included transportation as sled dogs, protection of food, or hunting assistance. There is also evidence that they played an important role in early Native American religious culture.
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 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 pointing at the food box, tapping it, or even simply glancing at it. Dogs almost always picked up on the signals and picked the right box, while chimps performed no better than chance. (Experimental controls ensured that dogs were not simply smelling the food.)
Hare, the Harvard PhD candidate who designed the study after trying it out on his own two dogs at home, 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 in 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 not found 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."
© 2002 The Washington Post Company
