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Text A. The Origin of Dogs

Where did our best friend originate? Researchers are looking to DNA to dig up answers about where, when and why pooches became popular

By Katherine Harmon

From Chihuahua to Great Danes, all domestic dogs (Canis familiaris) seem to be descended from the Eurasian gray wolf (Canis lupis). But what we still don't know is exactly when and where our best friends transformed from predators into partners. And such knowledge might help solve the long-disputed question of exactly why dogs were the first animal to be domesticated.

The dog genome was first decoded in 2005—and even before that researchers had been using genetic tools to track Fido's first home. Early research pointed toward east Asia as the locus of first taming after the discovery of high genetic diversity and other key markers in dog populations from various villages there. Some investigators, however, have since pointed out that the genetic search sampled more east Asian village dogs, neglecting similar pups roaming other villages around the globe. That's where the Village Dog Genetic Diversity Project at Cornell University comes in. Starting with a recent genetic analysis of dogs in African villages, the Cornell group hopes ultimately to create a detailed DNA-based map of canine ancestry worldwide, which in turn should provide a new understanding of the ancient humans who took them in.

One part of that new insight appeared earlier this month in the Proceedings of the National Academy of Sciences (PNAS), in a study that calls into question the assumption of dogs' east Asian origin. A team led by Adam Boyko, a researcher at Cornell's Carlos D. Bustamante Lab, sampled 318 village dogs in Africa (as well as hundreds of dogs from North America and Europe for comparison) and discovered that the high genetic diversity of canines there resembles that found in east Asia. "We found almost without exception they're descended from different ancestral populations," Boyko says of the village dogs sampled in Africa. That means they may have been there just as long as others had been in east Asia.

Researchers have also yet to figure out when people first began raising dogs. The going theory is that dogs were domesticated somewhere between 15,000 and 40,000 years ago. But, Boyko explains, genetic testing has not gone deep enough to come up with a more refined date. To try to track down some more clues, field crews have fanned out around the globe this summer to test village dogs in Vietnam, New Guinea, Malaysia and other locations in Eurasia in order to get more data.

Of course, scrappy village dogs aren't often the focus of heartfelt conservation efforts, and some even face active elimination programs. But these pups also have challenges from newly arrived European-descent dogs, which threaten to make a splash in the regional gene pool. "It is unclear the degree to which older populations will be able to maintain their genetic identity and persist in the face of modernity," Boyko and his co-authors wrote in the PNAS paper. So time is of the essence in digging up a solid answer about doggie descent.



Looking back into the pooch family tree will help researchers learn more not only about dogs, but about ancient people, as well. A genetic map of dog domestication could reveal important information about human migration and trade routes. "We may be able to turn dogs into a genetic marker for what human populations were doing," Boyko says. He adds that he and his colleagues also plan to "look for which regions of the genome went under selection earliest," and from that "we'll also learn what traits were selected for at that time." That knowledge, along with a little help from archaeologists, may be able to uncover sniff out just why the dog was so special and became most likely the first domesticated species. (From Scientific American Online, August 20, 2009)


Date: 2016-03-03; view: 101


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