A PBS documentary highlighted some of the remarkable differences between wolves and domesticated dogs (Nova: Dogs Decoded, video). The Nova segment is a remarkable distillation of recent evidence about how humans have altered dogs through artificial selection, and been altered ourselves in the process.
As I discussed in an earlier post, there is much controversy about how long our mutual admiration society has been in operation, with estimates ranging from about 10,000 to 100,000 years.
However long our association with dogs has gone on, we have altered them radically from ancestral wolves although they can still interbreed and are thus the same species. The primary factor that humans selected for was tameness, or low levels of aggression. The main mechanism through which this was accomplished was neotenization, or retention of juvenile low aggression into adult life. We also selected animals who paid attention to us.
The resulting differences between dogs and wolves are striking. When wolves were raised in human homes, they were a great deal more aggressive and less respectful of human rules. Although wolf cubs are cute, they quickly mature into wild animals who have little interest in their masters.
Apart from the more obvious anatomical signs of juvenility, such as shortened snout and more domed skull, adult dogs are remarkably sensitive to human social cues in a way that hand raised wolves are not.
Dogs are exquisitely sensitive to gestures, such as pointing, and are very good at finding hidden food when we point to it, something no other animal can do. Another uncanny canine capacity is their facility at reading our emotions. You don't have to tell your dog whether you have had a good day or not.
How dogs decode our emotions may be complex and is poorly understood. One of the more fascinating recent discoveries is that when dogs look at human faces, they gaze to their left, fixating the right side of our faces that convey more emotion than the left side.
In the course of exploiting their niche as our best friends forever, dogs evolved a varied repertoire of barks to signify various emotions. Wolves evidently have less range in their vocal repertoire although the Nova claim that they have only one bark (for anger) is a mistake (at least for pack animals in the wild). Recent research finds that domestic dogs have at least eight different barks that people can distinguish (e.g., when the dog is left alone, when it encounters a territorial threat, when it is frightened, or dejected).
If all of this were not enough, it seems that dogs are very much better at understanding our words than we are at deciphering their barks. Witness the border collie who recognizes words for some 300 different objects that it will fetch on demand.
It seems that the process of domestication has had profound genetic effects for dogs. Dogs also allowed our ancestors to become much more effective hunters and their services as herders likely played a role in domesticating other species.