Sometime between fifteen and thirty thousand years ago, probably in the Middle East, the long, protracted process of domestication began to alter the genetic code of the wolf, eventually leaving us with the animals we know and love as domestic dogs. While there are several different theories as to exactly how dog domestication began, what is clear is that there were some wolves who were less fearful of humans than others. Over time, those wolves were incorporated into early human settlements. Perhaps humans and early dogs learned to hunt cooperatively - both species hunt primarily by outrunning their prey - or perhaps early dogs instead learned that they could avoid hunting by scavenging on the leftovers of human hunting parties. Whatever the initial reason for the incorporation of wolves into human society, there their descendents still remain.
By sharing an environment with humans, dogs left behind their ancestral environment and found a place in a new one. No longer would they have to hunt to eat; humans would come to provide for their care and feeding. It is probably no accident that the relationship between dogs and their owners mirrors the attachment relationship between parents and their children, behaviorally and physiologically. Indeed, humans who have strong bonds with their dogs have higher levels of oxytocin in their urine than those with weaker bonds.
But it isn't only the source of their food that changed as wolves became dogs; their entire social ecology changed. Instead of sharing social space primarily with other wolves, dogs came to treat humans as social partners. This is one of the critical differences between a domesticate and a wild animal that is simply habituated to the presence of humans. Domestication is a genetic process; habituation is an experiential one. Domestication alters nature, habituation is nurture.
Several years ago, scientists at Eotvos University in Budapest wanted to determine whether the social-cognitive differences among dogs and wolves was primarily genetic or experiential. To do this, they hand-raised a group of dog puppies and a group of wolf pups from birth, resulting in roughly equivalent experiences. Any differences between the two groups' social cognitive skills, then, would be attributable to genetics.
Wolf and dog pups were raised by humans starting four to six days after birth, before their eyes had fully opened. For the first months of their lives, the wolf and dog pups were in close contact with their human foster parents nearly twenty-four hours per day. They lived in the homes of their caregivers and slept with them at night. They were bottle-fed, and starting on the fourth or fifth week of life, hand fed with solid food. Their human caregivers carried them in a pouch so that the wolf pups and dog puppies could participate in as much of their daily activities as possible: traveling on public transportation, attending classes, visiting friends, and so on. Each of the pups had extensive experience meeting unfamiliar humans, and at least twice a week, they were socialized with each other as well as with unfamiliar adult dogs. The guiding principle for the hand-rearing paradigm, according to the researchers, was based not upon competition or aggressive interactions, but "to behave rather like a mother than a dominant conspecific."
Would wolves, having been raised by humans, demonstrate social-cognitive skills that approached the sophistication of dogs? Or is social-cognitive aptitude encoded in dogs' genes, a direct result of domestication?
In one simple task, a plate of food was presented to the wolf pups (at 9 weeks) or to the dog puppies (both at 5 weeks and at 9 weeks). However, the food was inaccessible to the animals; human help would be required to access it. The trick to getting the food was simple: all the animals had to do was make eye contact with the experimenter, and he or she would reward the dog with the food from the plate. Initially, all the animals attempted in vain to reach the food. However, by the second minute of testing, dogs began to look towards the humans. This increased over time and by the fourth minute there was a statistical difference. Dogs were more likely to initiate eye contact with the human experimenter than the wolves were. This is no small feat; initiating eye contact with the experimenter requires that the animal refocus its attention from the food to the human. Not only did the wolf pups not spontaneously initiate eye contact with the human experimenter, but they also failed to learn that eye contact was the key to solving their problem.
A second experiment, conducted when the wolves and puppies were between four and eleven months old, found similar results. Each animal was presented, in different testing sessions, with two different types of tasks. First, each of the wolves and dogs was trained to retrieve a food reward by opening a bin (in one task) or pulling a rope (in the second task). Then, after they had mastered the task, they were presented with an impossible version of the same problem. After attempting to retrieve the food, the dogs looked back towards the human caregivers. The wolves did no such thing. Dogs spontaneously initiated a communicative interaction with the humans earlier, and maintained it for longer periods of time, than did the human-reared wolves, who all but ignored their human caregivers.
Both dogs and wolves were equally adept at learning the two tasks, indicating that there were no group differences in terms of motivation or physical abilities, but large differences emerged when given impossible problems to solve. In both impossible tasks, as well as in the earlier eye contact experiment, dogs instinctively shifted their attention away from the food and towards the humans. Despite the fact that they had been fully socialized, the wolves treated each of the situations as physical problems rather than social ones. Only rarely did they ever attempt to engage in a communicative problem-solving interaction with a human. It's not that wolves are unintelligent; it's quite the opposite, in fact. Wolves are cooperative hunters, skilled at negotiating within their own social networks. It's just that even after being raised by humans, wolves simply do not see humans as potential social partners. The dogs, however, quite rapidly took a social approach to solving each problem they were given. In one sense, this is a remarkable example of tool use. Only in this case, the humans were the tools, and the dogs the tool-users.
Gcsi M, Gyori B, Miklsi A, Virnyi Z, Kubinyi E, Topl J, & Csnyi V (2005). Species-specific differences and similarities in the behavior of hand-raised dog and wolf pups in social situations with humans. Developmental psychobiology, 47 (2), 111-22 PMID: 16136572
Miklsi A, Kubinyi E, Topl J, Gcsi M, Virnyi Z, & Csnyi V (2003). A simple reason for a big difference: wolves do not look back at humans, but dogs do. Current biology : CB, 13 (9), 763-6 PMID: 12725735