“Man’s Best Friend” is not a phrase humans throw about lightly. Horses, elephants, camels, donkeys, and even dolphins and pigeons have been put to work by humans, and deserve credit for helping to build civilization. These beasts not only worked hard assisting their human masters in everything from agriculture to construction to warfare, but they have also provided varying degrees of companionship. However, none of these creatures gets that all-important word “best”. This term of respect is reserved strictly for one single species: the dog, also known as Canis lupus familiaris.
Dogs enjoy a reputation apart from all other animals among humans. Dogs have repeatedly been cited for their unflagging loyalty, their obedience, their sense of duty, their intelligence, their bravery, their friendly demeanor, and their companionship. Pet dogs are often given the free run of the house in ways no other animal would; it is not uncommon for a dog to share a sofa or bed with its owner. Stories of legendary dogs, who selflessly committed acts of sacrifice for their owners have been passed through generations. Movies and books have been devoted to dogs, have told stories from the dog’s point of view, have glamorized dogs, and have largely portrayed them in a heroic or sentimental light.
The extinct European Wolf, a close relative to the familiar Gray Wolf, was a dangerous apex predator that was not particularly trustful or tolerant of humans. They were pack animals that stayed close to their own kind, and survived largely from viciously attacking weaker prey. The journey from feared hunter to the family pooch lolling on its back for a tummy-scratch is a long one, and one of the more compelling examples of natural selection and artificial selection.
The Gray Wolf evolved to become what it is today through the same natural selection that all other creatures undergo. The modern Gray Wolf is familiar to humans, but largely considered unsuitable as a pet. They are strong willed, independent, resistant to training or housebreaking, unpredictable around children, and dangerous when threatened or angry. Farmers have long despised the Gray Wolf because of the carnage it visits upon livestock. They are also prone to carrying rabies. However, it is the sole ancestor of the domestic dog, from the most wolf-like breeds such as Huskies, to the least wolf-like, like Chihuahuas. The Gray Wolf, or more accurately, individuals within the species, was eventually domesticated by humans in Europe between 20,000 to 30,000 years ago. This marked the beginning of the artificial selection of wolves, which eventually resulted in dogs.
However, before the Gray Wolf could be domesticated, it first had to become a Gray Wolf. Gray Wolves evolved from the extinct “Hare-Eating Wolf” (Canis lephophagus), which split into two descendants: gray wolves and coyotes. Canis lephophagus existed from about 1.8 million years ago to about 1.3 million years ago, and was a small canid with a narrow skull. Earlier creatures in this lineage include the Canis ferox, a very primitive canis species. Even earlier was the Eucyon, an omnivorous fox-like creature about which not much is known. Their ancestors were the Miacids, carnivores that lived about 60 million years ago. Throughout this lineage, these creatures generally became larger, bulkier, and had larger brains. A small creature like Canis ferox would not have been much of a threat to animals larger than itself, and would probably be unsuited to survive in the current environment. Gray Wolves, however, were found in almost all corners of the northern hemisphere until only very recently, with no real threats to its existence beyond humans. Despite a tremendous loss of natural habitat in recent years, the Gray Wolf is listed as one of the least endangered species in the world, largely due to its adaptability and mobility.
While its ancestors are not well known and not well understood, the Gray Wolf is one of the most studied animals in history. Although it is an apex predator, it has largely learned to avoid and fear humans. Thus, wolf attacks on humans are relatively rare, and more attributable to rabid animals. Early humans eventually realized that the danger from a single wolf could be minimized by providing it with food. If the wolves were well-fed, they would not be prone to prey on humans. In addition, there was a sanitary benefit to having the wolves eat leftover meat scraps. The wolves would remain in close proximity to the human encampment that was feeding them, establishing territory nearby that may have helped the human encampment avoid attack from other hostile humans. The benefits to the wolves were a reliable source of food, less caloric needs, more opportunity to breed, and warmth from human fires. This trade-off, meat and comfort for security and sanitation, was the first step towards domestication and later, breeding for desired traits.
There exists much disagreement about the circumstances of when and where the first domestication of the Gray Wolf took place, but evidence suggests it was during the last Ice Age, prior to the Neolithic revolution. Hunter-gatherers of the era were hunting mega-fauna, including mammoths, mastodons, and bison. Considering the potentially lethal dangers of such a hunt, having a pack of wolves at one’s disposal gave the human an important advantage during the hunt. There is also evidence that domestication was not always successful; it appears that the modern dog most likely evolved from multiple domestication attempts that were ultimately abandoned, rather than directly from the Gray Wolf itself. Although there is only a 1.8% genetic difference between dogs and wolves, dogs clearly have undergone radical changes in shapes and size, depending on the qualities later breeders were seeking.
Aside from their ability to hunt and provide security, wolves have other traits that make them desirable to humans. Wolves are social animals, which travel in packs and maintain a hierarchical relationship with one another. Wolves in the wild display loyalty to the pack under most circumstances, and are subservient to the alpha male. These were desirable traits in a companion to humans, as it suggested that if a human established a dominant position over the wolf, the wolf would obey him. The territorial nature of wolves, in which they define a territory much larger than what they need to survive as theirs, suggested that they would be useful as guards. Their strong sense of smell meant that they could track prey for humans. Their intelligence, and complex system of vocal and non-vocal communication, suggested that they would be able to understand commands or complex tasks. The only real drawback to wolves was their wildness; while some wolves were willing to be dominated by humans, others weren’t. Wolves would also unpredictably depart, or get into ferocious moods, which is probably why there were so many efforts to domesticate them; none fully worked for a long time, until generations of offspring later.
The artificial selection process was largely hit-and-miss at first, but over time, humans developed a strategy for domestication. Orphaned wolf pups were preferred; wolf pups raised by humans from 21 days of age or earlier can be easily tamed and domesticated. After multiple generations, these creatures became more dog-like in demeanor, while losing much of the wild behavior that is nature to wolves. Those adults who were attracted to humans by the proximity of food would have had varying temperaments, but those who were comfortable being among humans and feeding with them were more likely to produce offspring with similar comfort around humans. While the process probably took thousands of years, eventually dog-like wolves became commonplace. While the earliest successful domestication of wolves is still in dispute, researchers mostly agree that by 7000 BC, the modern dog had been born.
Physiologically, modern dogs generally are smaller than their wolf ancestors, and have shorter teeth. Some interbreeding may have occurred with coyotes as well, which are smaller than their wolf cousins. Early dogs would have been raised for hunting, guarding, and work primarily. Companionship, less of a necessity to early humans, probably developed over time as humans witnessed the reliability of dogs, and their loyalty to their owners. Dogs are relatively clean animals, so people were willing to keep them close by, even inside residences. All the dogs required for their service and loyalty was to be fed and cared for. The domestication of the wolf, and the artificial selection process that led to dogs is one of humankind’s most important developments, and stands as a striking example of interspecies cooperation.
The modern dog, as we know it, has been bred in many shapes and sizes. Some of these breeds are very large and lean, while others are low and squat. Some breeds were developed to accentuate the characteristics needed for herding. These dogs were bred for intelligence and aggression, and also for body shapes that would protect them from the animals they were herding. They are trained not to attack the herd, but to circle them endlessly and chase those that wander off back to the herd. Gun dogs are famous for accompanying hunters and helping to locate the prey, whereupon they will usually freeze in a pointing position. They are trained for retrieving, not attacking. Scent hounds are raised for their ability to detect scent, and will vocalize when the object of their hunt is discovered. These dogs will also not attack, but will instead summon humans. Mastiff-types are muscular and aggressive and are bred for their guard dog abilities, or for fighting. Sight hounds depend more on sight than scent in locating prey, and generally have better vision than other dog breeds (which, on the whole, is usually poor) Bulldogs are smaller, muscular, compact, squat dogs bred for combat. Terriers were also primarily hunters, generally bred for an elongated trunk but short legs, enabling them to follow prey into a burrow.
This specialization of dogs is quite remarkable. Unlike domestic cats, which largely serve no practical function beyond hunting rodents, dogs have been bred for a wide variety of uses. As humans have evolved, so too has the work evolved that we ask of dogs. Scent hounds were once primarily hunters, but now may find themselves working for the Drug Enforcement Agency. Sight hounds make good seeing-eye dogs. Dogs are very capable of adapting to new environments and new challenges, and will most likely remain man’s best friend as long as there are humans to raise them.
The road from the Eucyon to the Golden Retriever is a long one, and it required both a fortunate fifteen million years of natural selection as well as another ten thousand years of artificial selection. No other living creature has been so methodically bred to serve man, and no other creature seems quite as happy to serve man as the domestic dog.