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Dog Dynasty

DNA points south of Yangtze for first dog domestication

08·23·2015

Dog Dynasty

DNA points south of Yangtze for first dog domestication

08·23·2015

Be it a yapping shihtzu or a lumbering Tibetan mastiff, dogs have always been man’s best friend—or have they? Technically, at some moment in history, there was a point when man and dog were first united. But scientists are divided on how this union came to be.

One prominent academic, Peter Savolainen, from the Swedish KTH Royal Institute of Technology, has for over a decade been making the claim that the origin of dog domestication is in fact a region of China or Southeast Asia, south of the Yangtze River.

Essentially, there are a few ways scientists can trace the origins of a domesticated species. Archaeological research was the primary method for quite some time, however in the last few decades as the science for DNA analysis has become more sophisticated, analyzing the DNA for clues has become more applicable. But how does that work exactly? It’s not as if the DNA has a “Made in China” tag on it.

It’s rather the absence of DNA that makes the case. Savolainen points out that his research revolved around ten DNA types, three of which were found only within this region. “The only place you can expect to find all ten types is at the point of origin,” he says. “You have ten basic types among dogs. You have all the types in southern China and Southeast Asia. As soon as you go north of the Yangtze River we have found only seven. In north China, in Heilongjiang, we have found only five. In Japan we found seven—in Europe, four.”

But when he talks about these DNA types it is crucial to avoid associating this with the idea of various varieties of dog. “In this case, the DNA doesn’t code for any genes. It’s random junk DNA in a way. That is the perfect thing for looking at this kind of analysis, otherwise there might be selection. These don’t carry a function.”

In a number of papers in recent years, Savolainen and co-authors have made the case that the genetic diversity of dogs in this region south of the Yangtze River indicated that this was the cradle of dog-human civilization, with the first domestication of dogs occurring somewhere in a fairly wide window between 5,400 and 16,300 years ago.

The wide window is due to the fact that while using DNA is handy for determining the origin point of a domesticated species like this, it is not ideal for determining the exact period—in those cases, archaeology is needed. Given the results of archaeological findings, Savolainen estimates that the domestication event probably happened sometime between 10,000 to 15,000 years ago.

The DNA also can’t specifically explain the means by which the animals spread, though Savolainen said it was likely to have been trade, if the animals proved popular. But before this domestication can be notched up to another “Made-in-China” success, it’s probably wise to point out that according to Savolainen’s best guess, the dogs may well have been raised for food—a finding that perhaps reinforces certain unpalatable stereotypes. Given the transition into agriculture in the area at the time, it seemed likely that food was a primary reason for this domestication.

Savolainen first started researching this area after he noticed in 1999, during forensic analysis of dog hairs from a crime scene, that dogs from East Asia had their own unique genetic differences.

He got in touch with Professor Zhang Yaping in China for assistance in locating samples and began working with Zhang and Professor Wang Guodong, who are operating out of the State Key Laboratory of Genetic Resources and Evolution, and the Yunnan Laboratory of Molecular Biology of Domestic Animals, under the Kunming Institute of Zoology, Chinese Academy of Sciences.

Since then, across various studies, they collected 3,000 dog samples from around the world, with 500 from China. They hope to more precisely identify where dogs originated and also identify the specific genes which changed in the evolution from wolves to dogs.

Interestingly, dogs are not the only animal which, according to the DNA evidence, seem to have been domesticated in China. Pigs seem to have two different origin points from two different domestication events—one in the Middle East and one in China. According to genetic evidence, chickens also seem to have been domesticated in a similar region to dogs—somewhere south of the Yangtze River, either in China or Southeast Asia.

However, there are alternative theories circulating throughout the scientific community. Another study, published in Nature magazine, which also used DNA evidence as well as archaeological findings, puts the point of origin in the Middle East. This was more in line with previous theories on the origins of dogs which relied solely on archaeological evidence, but Savolainen points out that this study didn’t include samples from the region of Asia where this genetic diversity was found.

Issues relating to the number of DNA samples collected from various regions represent some of the key difficulties in analyzing the origins of dogs; some areas have been sampled extensively, while others are left almost untouched. This not only creates gaps in knowledge, but can also lead to biases as researchers develop assumptions. In addition, distinguishing between wolf bones and dog bones can be a highly specialized task, which can also easily result in wolves being incorrectly identified as dogs.


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