The social nature of wolves provides the evolutionary template for dogs. Wolves are highly social and live in a complex society maintained by systems of communication, cooperation, and aggressive and submissive behaviors. They exist in small family units consisting of a single reproductive (dominant or alpha) mated pair and their adult offspring from consecutive years. Some packs may also contain non-relatives or “strangers.”
Generally only the alpha pair reproduce, while adult offspring assist in all aspects of pack life including hunting, provisioning and guarding of offspring, defending pack territories, and attending to the den. Such packs maintain territories and aggressively repel interlopers—so aggressively, in fact, that interpack aggression may be the largest cause of non-human-induced mortality among wolves.
These wolfish behaviors are a kind of pre-adaptation for human/dog relations. Dogs can be readily submissive to their owners, but show various degrees of aggression toward strangers or territorial interlopers. They form long-term bonds with humans, as they would often do in a pack or with mates, and show cooperative and altruistic behavior, sacrificing for humans just as they would for kin.
How Old Is Our Oldest Friend?
Exactly when the dog split off from the wolf and hitched its future to that of humans is subject to debate, as are the reasons humans and wolves joined forces. The earliest archaeological evidence of dogs dates from 12,000 to 14,000 years ago. By 8,000 to 10,000 years ago dogs were found throughout the world, their presence increasingly recorded in early rock art from Africa, Eurasia, North America and Australia. This art shows them used for hunting and ceremonial purposes. Compared with wolves, these dogs possessed a foreshortened face, crowded teeth, a smaller brain, reduced bulla—the bony case surrounding the ear —and a prominent “stop,” or break between forehead and face.
But there is new evidence that the archaeological record does not tell the full story of the dog’s origin. Research by one of us (Robert Wayne and colleagues) on mitochondrial DNA, inherited through the mother and involved in the cell’s energy system, indicates that genetically the dog split from the wolf perhaps over 100,000 years ago and today differs in genetic (DNA) composition from the wolf by no more than 1 percent. This finding suggests that behavioral features may have been key in the domestication process and indicates that for much of the history of anatomically modern humans, there have been dogs.
The Domestication Question
Evidence suggests that ancient human hunters and gatherers had great respect for the abilities of top animal predators, like wolves and big cats, not least because they sought the same prey and probably scavenged each other’s kills. Proximity combined with the similar social structure of human clans and wolf packs doubtless created opportunities for humans to tame wolf puppies and for wolves to grow more accustomed to human encampments and activities. Wolves scavenging around the camps could also have warned of other predators and even driven them away.
Mutual tolerance and respect, combined with the proto-dogs’ willingness to submit to human direction, could well have set up the dynamic relationship that has changed and flourished through many human cultures and adaptations. Certainly the similarities between the wolf’s pack structure and the extended families of early humans made it easy for proto-dogs to fit into human societies.
Proto-dogs may have remained unchanged in appearance for tens of thousands of years, perhaps until what we know as the domestic dog began to appear in the fossil record. We know that many European travelers described the dogs of the Inuit and many North American Indian tribes as indistinguishable from wolves. That might reflect not only a lack of selection for traits we identify with dogs but also the intermingling of dogs and wolves. In this view, the look of proto-dogs began to change in places where people started to establish more permanent settlements and change their ways of living at the end of the last Ice Age.