There are four general theories on how the modern dog evolved: 1) from wolves tamed through human intervention 2) wolves “taming” themselves over a long association with humans 3) wolves dividing into distinct populations of wolves and proto-dogs through scavenging activities 4) modern dogs evolving from a wild dog or proto-dog species other than “Canis lupus”.
1) Human Intervention
Juliet Clutton-Brock proposed that wolves began their evolution into dogs approximately 12,000 to 14,000 years ago, coinciding with humans moving from hunter-gatherers to settled agrarians. Adult wolves, preying on humans and their food supplies would be driven away, but abandoned wolf pups would be taken as gifts for childless women or as playmates for children.
As the wolf puppies reached maturity, they would either escape back into the wild, or be killed and eaten, their pelts used for clothing. Occasionally, a particularly tame or highly favored mature wolf might be allowed to remain in the camp, interbreeding with other “pet” wolves; over several generations the ancestors of the modern dog evolved.
2) Self-taming Over Long Association
Dr. David Paxton proposes that the wolf-human relationship began 80,000 years ago, while humans were still nomadic hunter-gatherers. Wolves followed humans to take advantage of byproducts, and in exchange, provided protection against other predators. Gradually, human and wolf would have become co-dependents and accepting of each other’s presence. Paxton also proposes that Homo sapiens would not have survived it not for the additional protection and assistance the wolf/proto-dog provided.
3) Self-evolving Scavengers
Raymond Coppinger and Lorna Coppinger propose that individual wolves had a shorter flight distance (reaction to danger by when to run and how far), were less nervous, and these animals took advantage of the byproducts of the early settlements (12,000 to 14,000 years ago). More nervous individuals, with a longer flight distance (running early and farther from potential danger) removed themselves from human habitation, leaving the dump wolves to interbreed, eventually producing more tamable off-spring with virtually no flight distance – these became the early ancestors of modern dogs.
4) Janice Kohler-Matznick proposes that dog did not (directly) descend from “Canis lupus”, a specialist carnivore, but rather from a more generalist scavenger, a wild canine, closer to a modern dingo or pariah dog. The theory is that early man had neither the resources or the ability to successfully maintain tame a wolves, and that wolf behavior does not lend itself to domestication – therefore, dogs must have had a different ancestor.
The DNA evidence (documented by Dr. R.K. Wayne in a paper titled “Molecular evolution of the dog family”) indicates that dogs and wolves are closely related, but does this mean modern dogs are descended ONLY from ancient wolves? While there are genetic and behavioral similarities between dogs and wolves, there are also similarities between dogs and jackals, dingos, wild dogs and pariah dogs. There are instances of interbreeding in modern canine populations, so it is very likely interbreeding happened in the past as well.
Wolves are carnivores who require high-protein diets – wild dogs are scavengers and omnivores who require meat, but who can also make use of vegetation and waste products. Wolves mature more slowly than modern dogs and wild dogs, and early hunters and farmers would have to supply the young, growing animals with valuable, high-protein food for two years before the animals were useful for hunting or herding or before they could be bred to produce “tamer” animals.
Wolves prey on humans, as well as their wild game supplies and livestock. Humans and wolves are competitors, and the relationship would have been even more competitive 60,000 years ago, or even 14,000 years ago. A smaller scavenger would have posed little, if any, threat to hunting or herds, and any prey could be stolen by humans – it is likely the presence of a smaller canine would have been tolerated closer to human habitation.
Behaviorists working in ideal conditions are unable to completely tame and train wolves today. Just containing an adult wolf is a major logistical problem. Even wolf/dog hybrids are considered unstable, unsuited to training for specific tasks and are often escape artists. Wolf puppies must be handled by 19 days of age, or they will not accept humans. Early humans would not have had the resources or the knowledge to conduct a taming and breeding program on the scale required to turn wolves into dogs.
Though it is proposed that wolves were originally used as hunting partners, herders or guardians, this seems unlikely. Wolves hunt for themselves and are possessive of their kills. Wolves would be more likely to kill flocks than protect them. And again, training a wolf to follow a simple command like “sit” or “stay” is next to impossible – herding dogs and hunting dogs are highly bred dogs who require specialized training to be effective partners.
Although it is clear that wolves and dogs are related, the link is more likely through the interbreeding of different species or through an intermediary species (wild canine) than a direct descendance. The notion that our dogs are descended from the mighty wolf is romantic and perhaps more palatable than dogs descending from a scavenger, such as a jackal, however our dogs are opportunists rather than mighty hunters.
Even trained specialists with modern theories and tools find it impossible to train and and almost impossible to contain wolves or wolf-hybrids – it’s unlikely than early man would have had the ability or the foresight to train wolves for useful roles in human society. It is also unlikely that early man would have used essential food to support large numbers of animals until they could become useful partners, or that that humans would have formed a partnership with a species that so directly competed with us for essential resources.
Rather than all dogs being descended directly from wolves, it is more likely that dogs evolved from different canine ancestors, and as they lived and moved with human populations, their genes intermingled with other canines, including wolves, coyotes, dingos and jackals. The actual evolution of the wild ancestor into the modern dog was probably the result of a number of factors and events, rather than one simple chain of planned or “natural” evolution – and the process probably included elements from all of the standard theories on dog evolution.
References and suggested reading:
“Canine Behavior: A Guide for Veterinarians” by Bonnie Beaver
“Dogs A starling new understanding of canine origin, behavior & evolution” by Raymond Coppinger and Lorna Coppinger
“The Intelligence of Dogs” by Stanley Coren