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November 22, 2002 12:57 a.m. EST |
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DNA Data Indicate All Dogs By PETER LANDERS Somewhere in or near China about 15,000 years ago, a few docile gray wolves hit upon a good idea: Instead of tiring themselves out on the hunt all day, why not hang around the campfire of humans and pick up scraps of food there? Hunter-gatherer tribes were happy to have the wolves around, perhaps as guards or hunting companions, so long as they didn't act too wolflike. After many generations, a new breed of gray wolf emerged, a gentle race that could prosper only in human company. And prosper it did, traveling with human friends from its Asian homeland all the way to South America and Europe within a few thousand years. ... That could be the early history of the dog, according to scientists who are beginning to draw a detailed picture of the time when humankind's best friend was first befriended. To the delight of dog lovers, the emerging picture puts dogs on center stage during many milestones of human prehistory, from the formation of settlements to the great post-Ice Age migrations. A new piece of the picture comes in Thursday's issue of the journal Science, in which researchers suggest that the dog may have originated in East Asia, rather than Europe or the Middle East as commonly assumed. A second article in Science says genetic evidence shows dogs colonized the New World together with humans, trotting their way across the land bridge to Alaska some 12,000 years ago. "Dogs must have played some essential role in these early human societies," says Robert Wayne, a biology professor at the University of California at Los Angeles and co-author of the second paper. "Dogs are a nice companion but an expensive companion. They eat meat. Humans were willing to pay the price." Both of the Science papers confirm the results of earlier research that the various breeds of dogs today are virtually identical in genetic terms both to each other and to wild gray wolves, despite their vastly different appearances. Studies of domesticated animals have shown that a few small genetic modifications can have broad effects. Domesticated animals, including dogs, tend to retain a more juvenile appearance and develop features such as floppy ears and tails that are rarely found in the wild. Humans and gray wolves have shared habitats and hunting grounds for millennia, but scientists generally agree they began to get serious about their relationship roughly 15,000 years ago, when some humans were beginning to establish settlements. It's not clear who made the first overture, but in recent years dog experts have favored the wolf. For wolves that were good scavengers and relatively docile, taking up with humans might have been a good survival strategy. "I think dogs initiated the movement into those villages," says Raymond Coppinger, a biology professor at Hampshire College in Amherst, Mass., and author of a recent book on dog history. Dr. Coppinger scoffs at romantics who imagine early humans taking in cute wolf pups. "I'm not sure that Mesolithic people could go down to the drugstore and buy a rubber nipple," he says. Why didn't humans drive the early dogs away? Perhaps the animals were useful trash collectors. Soon, though, humans must have realized that dogs could help out as camp guards, hunters and beasts of burden. People might have used dogs for food, too. The uses are so manifold that many scientists have long assumed the domestication of dogs happened independently many times around the world. Not so, according to the new research led by Peter Savolainen at the Royal Institute of Technology in Stockholm. Dr. Savolainen examined mitochondrial DNA from 654 dogs world-wide in an attempt to determine their origin. His data show the most genetic diversity among dogs in East Asia, suggesting domestication happened there first. In this view, all dogs today descend from East Asian dogs who traveled across the continents with humans. Dr. Savolainen says it's plausible to assume that a single group of people living around 15,000 years ago initiated the domestication. That conclusion is controversial; critics say Dr. Savolainen's team didn't test enough European and Middle Eastern dogs to say with certainty that diversity there is lower. Still, the mention of East Asia is a surprising twist and is likely to lead scientists to ask why that might have been a plausible location for the first domestication. Dr. Savolainen says it may be because East Asian gray wolves are smaller and more easily domesticated. Zhang Yaping, a researcher at the Kunming Institute of Zoology in China who collaborated on Dr. Savolainen's study, thinks East Asia might have been a hotbed of domestication at the time. He is also examining the genetic roots of pigs, chickens, cattle and yak. "Domestication is one of the important factors in the transition to a farming society," Dr. Zhang says. Wherever dogs got their start, it's clear they hit it off with humans quickly. Within a historical eye-blink, dogs spread across the planet. That's shown in a second paper in Science that illuminates the history of dogs in the Americas. Jennifer Leonard, a UCLA geneticist in Dr. Wayne's lab, and colleagues in the U.S. and Latin America tested mitochondrial DNA from modern dogs as well as from the bones of 37 dog specimens from archeological sites in Mexico, Peru and Bolivia. Their conclusion: When humans first entered the Americas 12,000 to 14,000 years ago, they brought dogs with them. The genetic data show that ancient American dogs resembled their Eurasian counterparts and didn't appear to have come from American gray wolves. The study also suggests that Native American dogs were wiped out after Europeans and their dogs arrived in the New World. Write to Peter Landers at peter.landers@wsj.com1
Updated November 22, 2002 12:57 a.m. EST |
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![[dog map]](http://www.wsj.com/public/resources/images/2f_dogs11222002005052.gif)