DNA studies suggest domestication happened south of the Yangtze River up to 15,000 years ago

DNA证据显示，人类和狗最早的友谊很可能发源于长江以南

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 about.

One prominent academic, Peter Savolainen, from the Swedish KTH Royal Institute of Technology, has for over a decade claimed that the origins of the domestic dog lay in 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 some time. However, in the past few decades, as the science of DNA has become more sophisticated, analyzing 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. Rather it is the absence of DNA that makes the case.

Savolainen points out that his research revolved about 10 DNA types, three of which were found only within this region.

"The only place you can expect to find all 10 types is at the point of origin," he says. "You have 10 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 you find only seven. In Northeast China, in Heilongjiang province, we 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 is random junk DNA in a way. That's the perfect thing for looking at this kind of analysis, otherwise there might be selection. These don't carry a function."