The authors say the process by which humans domesticated the dog is poorly understood.
Having been a beagle owner for over 20 years, I can tell you up front, they are looking at it backwards. I've been quite convinced that the ancestor of the beagle, saw us sitting at a fire, eating food, and thought: how do I get some of that?
When I married my husband, his beagle had completely trained him -- if I give you a sock, you'll give me something to eat.
In fact, the most effective means of training both dogs and cats involve a give and take situation -- also know as clicker training. Both parties think they are training each other, so both parties are happy and get what they want.