There is an article in today's New York Times claiming that dogs were first domesticated in China, solely for a food source. And before you get your dander up (I felt mine starting to rise as I began reading this), this research contradicts prior research that indicated a number of different domestication events and separated dogs into groups based on those events. These is even current ongoing research that contradicts this report. So take it with a definite grain of salt and without the dog meat.
Whatever the value of this report, the domestication of dogs remains a topic of fascination. Ray Coppinger's theory that wolves domesticated themselves, scavenging at human garbage dumps, seems plausible. And presumably the humans quickly realized the advantages of having wolf dogs around (alarm barking is often cited, though wolves rarely bark, so keeping the settlement cleaner and relatively free of vermin may be more likely, plus the "three-dog night" warmth of furry bodies). Co-hunting and alarm barking probably came later, as wolves morphed into dogs.
The current study investigated only mitochondrial DNA. Other studies surveyed a wider spectrum of DNA and so probably have more validity. But it remains an open question and research is ongoing. Stay tuned.