Canine Evolution

I found this L. A. Times article fascinating. Apparently, millennia of interaction with humans have shaped the genetic code of domesticated dogs in surprising ways.

In the genetic journey from wolf to lapdog, dogs developed a unique genius for sensing human intentions, as the interplay of handler and hound shaped the biology of canine behavior in ways that scientists only now are beginning to understand, new research shows. … From birth, dogs are fluent in the human text of hand gestures and facial expressions. Their ability to understand humans is better than chimpanzees -- humanity's closest relative -- or the gray wolves from which dogs are descended, according to the first direct comparison of the species.

What's most intriguing to me about this (though the article doesn't discuss it) is that it blurs the line between natural selection and artificial selection. Symbiotic relationships are a well established part of biological evolution, and nobody would suggest that those birds that instinctively pick the teeth of hippos are the result of the hippos' attempts at artificial selection. So what, exactly, is different about the relationship between humans and dogs? Is it the fact that people have *deliberately* bred dogs to have certain traits? That's true, but this article draws attention to the many traits of dogs that arose from interaction with humans without deliberate human selection, but as a corollary to it. Dogs with a greater ability to sense human needs and emotions were more likely to survive, even if humans didn't specifically try to breed in those abilities. So where does artificial selection end and natural selection begin (or vice versa)?