It's pretty obvious in Darwin's thinking - and in the view of today's naturalists - that humans have influenced the evolution of the domestic dog. But an equally interesting hypothesis is Darwin's belief in the power of dogs to shape human evolution.
Derr quotes Darwin from The Descent of Man:
"The strongest and most vigorous men—those who could best defend and hunt for their families, who were provided with the best weapons and possessed the most property, such as a large number of dogs or other animals—would succeed in rearing a greater average number of offspring than the weaker and poorer members of the same tribes. There can, also, be no doubt that such men would generally be able to select the more attractive women."
I am curious to hear what my wife's thoughts will be.