Inside of a Dog: What Dogs See, Smell, and Know (6 page)

All these physical characteristics came along for the ride, once a particular behavior was chosen and picked out. The behavior is not what affects the body; instead, both are the common result of a gene or set of genes. Single behaviors aren't dictated by genes, but they are made more or less likely by them. If someone's genetic makeup leads to having very high levels of a stress hormone, for instance, it doesn't mean that they will be stressed all the time. But it may mean that they have a lowered threshold for having the classic stress response—a raised heart rate and breathing rate, increased sweating, and so on—in some contexts where someone else doesn't have a stress response. Let's say this low-threshold character screams at her dog for barreling into her at the dog park. Her screaming at the poor pup certainly is not genetically obliged—genes don't know from dog parks, or even pups—but her neurochemistry, created from her genes, facilitated it happening when a situation presented itself.

So, too, with the doglike foxes. Given what genes do,* even a small change in a gene—turning on slightly later than it otherwise might, say—could change the likelihood of both certain behaviors and certain forms of physical appearance. Belyaev's foxes show that a few simple developmental differences can have a wide-ranging effect: for instance, his foxes open their eyes earlier and show their first fear responses later, more like dogs than wild foxes. This gives them a longer early window for bonding with a caretaker—such as a human experimenter in Siberia. They play with each other even when they reach adulthood, perhaps allowing for longer and more complex socialization. It is worth noting that foxes diverged from wolves some ten to twelve million years ago; yet in forty years' of selection they look domesticated. The same perhaps could happen with other carnivores we take under our wing and inside our houses. The genetic changes nudge them into being doggy.

Though we tend not to think much about it, the history of dogs, well before you got your dog, bears more on what your dog is like than the particulars of his parentage. Their history begins with wolves.

Wolves are dogs before the accoutrements. The coat of domestication makes dogs quite different creatures, however.* While a pet dog gone missing may not survive even a handful of days on his own, the anatomy, instinctual drive, and sociality of the wolf combine to make it very adaptable. These canids can be found in diverse environments: in deserts, forests, and on ice. For the most part, wolves live in packs, with one mating pair and from four up to forty younger, usually related wolves. The pack works cooperatively, sharing tasks. Older wolves may help raise the youngest pups, and the whole group works together when hunting large prey. They are very territorial and spend a good amount of time demarcating and defending their borders.

Inside some of these borders, tens of thousands of years ago, human beings began to appear.
Homo sapiens,
having outgrown his
habilis
and
erectus
forms, was becoming less nomadic and beginning to create settlements. Even before agriculture began, interactions between humans and wolves began. Just how those interactions played out is the source of speculation. One idea is that the humans' relatively fixed communities produced a large amount of waste, including food waste. Wolves, who will scavenge as well as hunt, would have quickly discovered this food source. The most brazen among them may have overcome any fear of these new, naked human animals and begun feasting on the scraps pile. In this way, an accidental natural selection of wolves who are less fearful of humans would have begun.

Over time, humans would tolerate the wolves, maybe taking a few pups in as pets, or, in leaner times, as meat. Generation by generation, the calmer wolves would have more success living on the edge of human society. Eventually, people would begin intentionally breeding those animals they particularly liked. This is the first step of domestication, a remaking of animals to our liking. With all species, this process typically occurs through a gradual association with humans, whereby successive generations become more and more tame and finally become distinct in behavior and body from their wild ancestors. Domestication is thus preceded by a kind of inadvertent selection of animals who are nearby, useful, or pleasing, allowing them to loiter on the edges of human society. The next step in the process involves more intention. Those animals who are less useful or liked are abandoned, destroyed, or deterred from hanging about with us. In this way, we select those animals who more easily submit to our breeding of them. Finally, and most familiar, domestication involves breeding animals for specific characteristics.

Archeological evidence dates the first domesticated wolf-cum-dog at ten thousand to fourteen thousand years ago. Dog remains have been found in trash heaps (suggesting their use as food or property) and in grave sites, their skeletons curled up aside human skeletons. Most researchers think dogs began to associate with us even earlier, maybe many tens of thousands of years ago. There is genetic evidence, in the form of mitochondrial DNA samples,* of a subtle split as long as 145,000 years ago between pure wolves and those that were to become dogs. We could call the latter wolves protodomesticators, since they had themselves changed behaviorally in ways that would later encourage humans' interest (or merely tolerance) of them. By the time humans came along, they might have been ripe for domesticating. The wolves taken up by humans were probably less hunters than scavengers, less dominant and smaller than alpha wolves, and tamer. In sum, less wolfy. Thus, early in the development of ancient civilizations, thousands of years before domesticating any other animal, humans took this one animal with them inside the walls of their fledgling villages.

These vanguard dogs would not be mistaken as members of one of the hundreds of currently recognized dog breeds. The short stature of the dachshund, the flattened nose of the pug—these are the results of selective breeding by humans much later. Most dog breeds we recognize today have only been developed in the last few hundred years. But these early dogs would have inherited the social skills and curiosity of their wolf ancestors, and would then have applied them toward cooperating with and appeasing humans as much as toward each other. They lost some of their tendency toward pack behavior: scavengers don't need the proclivity to hunt together. Nor is any hierarchy relevant when you might live and eat on your own. They were sociable but not in a social hierarchy.

The change from wolf to dog was striking in its speed. Humans took nearly two million years to morph from
Homo
habilis
to
Homo
sapiens,
but the wolf leapfrogged into dogness in a fraction of the time. Domestication mirrors what nature, through natural selection, does over hundreds of generations: a kind of artificial selection that hurries up the clock. Dogs were the first domesticated animals, and in some ways the most surprising. Most domestic animals are not predators. A predator seems like an unwise choice to take into one's home: not only would it be difficult to find provisions for a meat eater, one risks being seen as meat oneself. And though this might make them (and has made them) good hunting pals, their main role in the last hundred years has been to be a friend and nonjudgmental confidant, not a worker.

But wolves do have features that made them terrific candidates for artificial selection. The process favors a social animal who is behaviorally flexible, able to adjust its behavior in different settings. Wolves are born into a pack, but only stay until they are a few years old: then they leave and find a mate, create a new pack, or join an already existing pack. This kind of flexibility to changing status and roles is well suited to dealing with the new social unit that includes humans. Within a pack or moving between packs, wolves would need to be attentive to the behavior of packmates—just as dogs will need to be attentive to their keepers and sensitive to their behavior. Those early wolf-dogs meeting early human settlers would not have benefited the humans much, so they must have been valued for some other reason—say, for their companionship. The openness of these canids allowed them to adjust to a new pack: one that would include animals of an entirely different species.

And so some wolflike ancestor of both wolves and dogs took the plunge, loitered among human loiterers, and was eventually adopted and then molded by humans instead of solely by the caprice of nature. This makes present-day wolves an interesting comparison species to dogs: they likely share many traits. The present-day wolf is not the ancestor of the dog; though wolves and dogs share a common ancestor. Even the modern wolf is likely quite different than the ancestral wolves. What is different between dogs and wolves is probably due to what made some protodogs likely to be taken in, plus whatever humans have done in breeding them since.

And there are many differences. Some are developmental: for instance, dogs' eyes don't open for two or more weeks, whereas wolf pups open their eyes at ten days old. This slight difference can have a cascading effect. Generally, dogs are slower to develop physically and behaviorally. The big developmental milestones—walking, carrying objects in the mouth, when they first engage in biting games—come generally later for dogs than for wolves.* This small difference blossoms into a large difference: it means that the window for socialization is different in dogs and wolves. Dogs have more leisure to learn about others and to become accustomed to objects in their environment. If dogs are exposed to non-dogs—humans or monkeys or rabbits or cats—in the first few months of development, they form an attachment to and preference for these species over others, often trumping any predatory or fearful drive we might expect them to feel. This so-called
sensitive
or
critical
period of social learning is the time during which dogs will learn who is a dog, an ally, or a stranger. They are most susceptible to learning who their peers are, how to behave, and associations between events. Wolves have a smaller window during which to determine who is familiar and who is foe.

There are differences in social organization: dogs do not form true packs; rather, they scavenge or hunt small prey individually or in parallel.* Though they don't hunt cooperatively, they are cooperative: bird dogs and assistance dogs, for instance, learn to act in synchrony with their owners. For dogs, socialization among humans is natural; not so for wolves, who learn to avoid humans naturally. The dog is a member of a human social group; its natural environment, among people and other dogs. Dogs show what is called with human infants "attachment": preference for the primary caregiver over others. They have anxiety at separation from the caregiver, and greet her specially on her return. Though wolves greet other members of the pack when they reunite after being apart, they don't seem to show attachment to particular figures. For an animal who is going to be around humans, specific attachments make sense; for an animal who lives in a pack, it is less applicable.

Physically, dogs and wolves differ. While still quadrupedal omnivores, the range of body types and sizes among dogs is extraordinary. No other canid, or other species, shows the same diversity of body types within a species, from the four-pound papillon to the two-hundred-pound Newfoundland; from slender dogs with long snouts and whiplike tails to pudgy dogs with foreshortened noses and stubs of tails. Limbs, ears, eyes, nose, tail, fur, haunches, and belly are all dimensions along which dogs can be reconfigured and still be dogs. Wolves' sizes, by contrast, are, like most wild animals, fairly reliably uniform in a particular environment. But even the "average" dog—something resembling a prototypical mutt—is distinguishable from the wolf. The dog's skin is thicker than wolves'; while both have the same number and kind of teeth, the dog's are smaller. And the whole head is smaller on a dog than on a wolf: about 20 percent smaller. In other words, between a dog and a wolf of similar body size, the dog has the much smaller skull—and, correspondingly, a smaller brain.

This latter fact has continued to be promulgated, perhaps an indication of the ongoing appeal of the claim (now debunked) that brain size determines intellect. While erroneous, the smoothness of the shift from talking about brain
size
to brain
quality
trumped evidence to the contrary. Comparative studies with wolves and dogs on problem-solving tasks initially seemed to confirm dogs' cognitive inferiority. Hand-raised wolves tested on their ability to learn a task—to pull three ropes from an array of ropes in a particular order—well outperformed the dogs tested. The wolves more quickly learned to pull any rope to begin and then proceeded to be more successful at learning the order in which the ropes were to be pulled. (They also tore more ropes to pieces than the dogs did, although the researchers are silent about what this indicates about their cognition.) Wolves are also great at escaping from enclosed cages; dogs are not. Most canid researchers agree that wolves pay more attention than dogs do to physical objects and handle these objects more capably.