Canine diaspora from East Asia to Americas. (Three Dog Eves).
Analysis of 654 dogs from around the world suggests that their earliest female ancestors originated from several lineages of wolves primarily in one region, says Peter Savolainen of the Royal Institute of Technology in Stockholm. The patterns of genetic diversity point to East Asia as the likeliest place for the canine Eden, Savolainen and his colleagues argue in the Nov. 22 Science.
"This has been the search for the dog Eve," says Savolainen.
The same issue of Science also reports on extraction of bits of DNA from New World-dog remains predating European influence. This DNA shows that early New Worlders did not domesticate dogs anew, say Jennifer Leonard of the Smithsonian Institution in Washington, D.C., and her colleagues.
"The first Americans came across the Bering land bridge with their dogs, and this was something we couldn't prove before," says coauthor Robert K. Wayne of the University of California, Los Angeles.
Dogs were probably the first domesticated animals (SN: 6/28/97, p. 400) and have unusual sensitivity to signals from people (see "Dog sense: domestication gave canines innate insight into human gestures").
Savolainen started studying dog genetics to help crime-scene investigators analyze hairs. "I've been to a lot of dog shows here, snatching hairs from the dogs," he says.
As he assembled a large collection of dog hairs and attached cells, he began to wonder whether he could expand it and find the cradle of the domestic dog.
He and his international partners focused on stretches of DNA from the cells' mitochondria, or powerhouses, which pass from mother to pup. Based on similarities in that genetic material, 95 percent of the dogs that the researchers had sampled tome from just three lineages that seem to have arisen in East Asia, Savolainen and his colleagues say.
To study New World dogs, Leonard and her colleagues worked with DNA from remains up to 1,400 years old. Thirty-seven came from archaeological sites in Peru, Bolivia and Mexico, and 11, from modern gold mines in the Alaskan permafrost.
When the researchers constructed a family tree that includes modern dogs and wolves, they found that the ancient New Word dogs were much closer to Old World dogs than to New Word wolves. Also, the ancient New Word lineages seem to have disappeared from modern breeds.
The two new studies agree with suggestions from older work: Dogs were domesticated in the Old World, and the earliest migrants brought them to the New World, comments geneticist David Hillis of the University of Texas at Austin. He is convinced by the new data that the major lineages of dogs originated in East Asia, but he sees evidence in the Savolainen study that some rarer lineages evolved elsewhere.
RELATED ARTICLE: Dog sense: domestication gave canines innate insight into human gestures.
Anybody who's ever moved a muscle toward a leash will agree that dogs understand human body language. The animals' capacity to do this, suggests new research, was evolutionarily engrained since they became people's canine companion about 15,000 years ago.
Previous studies have shown that dogs can use human cues to find hidden food. For example, dogs that watch experimenters look or point at a sealed bowl enclosing a meal then choose correctly between that container and an empty one. "Conventional wisdom would say that [people] train dogs to do this," explains Michael Tomasello, a comparative psychologist at the Max Planck Institute in Leipzig, Germany. But his team's findings support another view.
Tomasello and his colleagues compared various animals taking the food-container challenge. Dogs were always better than human-reared wolves at finding the food. And they even outwitted chimpanzees. The research team was surprised to final that 9-to-26-week-old puppies, including some rarely exposed to people, could use the researchers' cues to find food.
In the Nov. 22 Science, the researchers conclude that dogs don't learn social and communication skills from people nor do they inherit them from wolves, their closest relatives. They acquired the skills as they evolved in domestication (see story above).
Mark Plonsky of the University of Wisconsin-Stevens Point disagrees. He suggests that all the dogs in the study could have learned the skills. Even the puppies were old enough to have learned them from their mothers and littermates, he says.
In contrast, Benjamin Hart of the University of California, Davis says that dogs might learn from experience but that "they're also predisposed genetically" to understand people's cues.
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|Date:||Nov 23, 2002|
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