When we brought our new baby home from the hospital, our dog Tassie was faced with a dilemma. Since the day we adopted him from a shelter as a puppy, Tassie has had a basket of stuffed toys. Growing up, his favorite activity was to rip out the stuffing and leave it all over the house. Every now and then we would fill up the basket with new toys he could rip up all over again.
We also gave our baby, Malou, a basket of stuffed toys, which was almost identical to Tassie’s. As Malou started to crawl, she quickly developed the habit of dragging the toys out of her basket and leaving them all over the house.
Here was the dilemma. Of the dozens of toys, Tassie had to figure out which ones were his to rip up, or Malou was going to find her favorite toys in a heap of stuffing and there would be trouble.
Tassie turned out to be rather good at it. Of course, we were hopeful Tassie would have this ability, since Brian’s colleague at the Max Planck Institute for Evolutionary Anthropology in Germany, Juliane Kaminski, studied a dog named Rico who had solved a similar problem. Kaminski received a phone call one day from a very nice German lady saying she had a Border collie who understood more than two hundred German words, mostly the names of children’s toys. This was impressive but not unheard of. Language-trained bonobos, bottlenose dolphins, and African grey parrots have learned a similar number of names for objects. What was different about Rico was how he learned the names of these objects.
If you show a child a red block and a green block, then ask for “the chromium block, not the red block,” most children will give you the green block, despite not knowing that the word chromium can refer to a shade of green. The child inferred the name of the object.
Kaminski gave Rico a similar test. She placed a new object Rico had never seen before in a different room with seven of his toys that he knew by name. Then she asked him to fetch a toy using a new word he had never heard before, like Sigfried. She did this with dozens of new objects and words.
Just like children, Rico inferred that the new words referred to the new toys.
Without any training, Tassie has never ripped up one of Malou’s toys instead of his own. His toys and her toys can be lying in a jumble on the floor, and he will carefully extract his toys and play with them, giving her toys only a longing glance or a quick sniff. He adapted quicker than we did to life with a new baby.
* * *
In the last ten years, there has been something of a revolution in the study of canine intelligence. We have learned more about how dogs think in the past decade than we have in the previous century.
This book is about how cognitive science has come to understand the genius of dogs through experimental games using nothing much more high-tech than toys, cups, balls, and anything else lying around the garage. With these modest tools, we have been able to peer into the rich cognitive world of dogs and how they make inferences and flexibly solve new problems.
Thinking about dog genius will not only help us enrich their lives but also broaden how we think about human intelligence. Many of the same concepts used to study dog intelligence are being applied to humans. Perhaps the greatest gift our dogs will give us is a better understanding of ourselves.
Everyone has an opinion about what makes dogs smart. There is now an extensive scientific literature examining dog psychology that sometimes supports or doesn’t support these opinions. To help all dog lovers debate what the latest scientific findings might mean, this book provides a comprehensive review of dog cognition, or “dognition.”
We have read thousands of scientific papers relevant to the study of dog cognition, and we reference more than six hundred of the most important and interesting of these papers in this book. If you are interested, there are ways to get access to these papers and read them for yourself.*
While our review is comprehensive, it covers only areas that have been scientifically studied. We may not cover some areas of interest simply because no scientist has published anything on the topic. But on the flip side, there is tons of fascinating research on dognition you may never have imagined.
Although we have done our best to represent the literature fairly, not every scientist will agree with everything we report. Whenever we could, we highlighted alternative perspectives or competing data in the main text. But for ease of reading, we have provided extensive notes at the back of the book that cover important details and alternative findings when they are available.
Disagreement and debate in science are healthy and exciting. Disagreement often drives research that leads to advances in our understanding. Scientists rely on skepticism and empirical debate as a road to the truth. So do not be alarmed if your intuition or your own observations lead you to be skeptical of some of the evidence we present. You are just being a good scientist.
We hope that when you finish this book, your new knowledge, combined with your own observations, will lead to interesting discussions and debates with your fellow dog lovers. Through these debates, we can learn how to have an even richer relationship with our dogs. We can also identify areas where we need more understanding or where scientists have not even asked the right questions. This is all part of the fun.
What we know for certain is that the cognitive world of every dog is far more complex and interesting than we thought possible. We also have a tantalizing glimpse into the secret of their success. We can now pinpoint the stuff of dog genius.
Brian had the good fortune to play a significant role in the unfolding of this story of discovery—as did his childhood dog Oreo. Some of what is laid out in the following pages will shock even the most knowledgeable dog owners. It is not always obvious where dogs will show an ability to make inferences or show more flexibility than other species. But in the end, your intuition is correct—your dog is a genius.
The many flavors of genius
Can I really be serious about the title? Most dogs can do little more than sit and stay, and can barely walk on a leash. They are baffled when a squirrel disappears up a tree by circling the trunk, and most will happily drink out of the toilet bowl. This is not the profile of a typical genius. Forget Shakespearean sonnets, spaceflight, or the Internet. If I used the clichéd definition of genius, this would be a very short book.
I am serious, and hundreds of studies and the latest research back me up. This is because in cognitive science, we think about intelligence in animals a little differently. The first thing we look at, when judging the intelligence of animals, is how successfully they have managed to survive and reproduce in as many places as possible. In some species, such as cockroaches, success does not have much to do with intelligence at all. They are just very hardy and excellent reproducers.
But with other animals, surviving takes a little more intellect, and a very specific kind of intellect. For instance, it does not do any good composing sonnets if you are a dodo. You are obviously missing the intelligence you need to survive (in the dodo’s case, this was learning to avoid new predators such as hungry sailors).
With this as our starting point, the dog is arguably the most successful mammal on the planet, besides us. Dogs have spread to all corners of the world, including inside our homes, and in some cases onto our beds. While the majority of mammals on the planet have seen a steep decline in their populations as a result of human activity, there have never been more dogs on the planet than today. In the industrialized world, people are having fewer children than ever but are simultaneously providing an increasingly lavish lifestyle for a growing population of pet dogs. Meanwhile, dogs have more jobs than ever. Service dogs assist the mentally or physically disabled, military dogs find bombs, police dogs do guard duty, customs dogs detect illegally imported goods, conservation dogs find scat to help estimate population sizes and movements of endangered animals, bedbug dogs detect when hotels have a problem, cancer dogs detect melanomas or even intestinal cancer, therapy dogs visit retirement homes and hospitals to lift spirits and speed recoveries.
I am fascinated with the kind of intelligence that has allowed dogs to be so successful. Whatever it is—this must be their genius.
What Is Genius?
Most of us have at some time been given a test where scores determine how we are taught or which college we get into. Alfred Binet designed the first standardized intelligence tests in the early twentieth century. His goal was to identify students in France who should receive extra scholastic attention and resources. His original test evolved into the Stanford-Binet Intelligence Scale, which is known as the IQ test.
IQ tests provide a very narrow definition of genius. As you probably remember, tests such as IQ tests, GREs, and SATs focus on basic skills like reading, writing, and analytical abilities. The tests are favored because on average, they predict scholastic success. But they do not measure the full capabilities of each person. They do not explain Ted Turner, Ralph Lauren, Bill Gates, and Mark Zuckerberg, who all dropped out of college and became billionaires.
Consider Steve Jobs. One biographer said, “Was he smart? No, not exceptionally. Instead he was a genius.” Jobs dropped out of college, went to find himself in India, and at one point was forced out of Apple, the company he co-founded, when sales were slow in 1985. Few would have predicted the level of his success by his death. “Think different” became the slogan of a multinational monolith that fused art and technology under his guidance. Jobs may have been average or unexceptional in many domains, but his vision and ability to think differently made him a genius.
A cognitive approach is about celebrating different kinds of intelligence. Genius means that someone can be gifted with one type of cognition while being average or below average in another.
Temple Grandin, at Colorado State University, is autistic yet is also the author of several books, including Animals Make Us Human, and has done more for animal welfare than almost anyone. Although Grandin struggles to read people’s emotions and social cues, her extraordinary understanding of animals has allowed her to reduce the stress of millions of farm animals.
The cognitive revolution changed the way we think about intelligence. It began in the decade that all social revolutions seemed to have happened, the sixties. Rapid advances in computer technology allowed scientists to think differently about the brain and how it solves problems. Instead of the brain being either more or less full of intelligence, like a glass of wine, the brain is more like a computer, where different parts work together. USB ports, keyboards, and modems bring in new information from the environment; a processor helps digest and alter the information into a usable format, while a hard drive stores important information for later use. Neuroscientists realized that, like a computer, many parts of the brain are specialized for solving different types of problems.
Neuroscience and computer technology highlighted the fatal flaws in the idea of a single-dimensional measure of intelligence. People with well-tuned perceptual systems might be gifted athletes or artists; people with less sensitive emotional systems will succeed as fighter pilots or in other high-risk jobs; and those with unusual memories might do well as doctors. This same phenomenon can be observed in mental disorders. There are myriad cognitive abilities that are not necessarily interdependent on one another.
One of the best-studied cognitive abilities is memory. In fact, we usually think of geniuses as people who have an extraordinary memory for facts and figures, since such people often score off the charts in IQ tests. But just as there are different types of intelligence, there are different types of memory. There is memory for events, faces, navigation, things that occurred recently or long ago—the list goes on. If you have a good memory in one of these areas, it does not necessarily mean your other types of memory are equally as good.
For instance, a woman known as AJ (to protect her identity) had a remarkable autobiographical memory. She could remember when and where almost everything happened in her life. When experimenters named various dates, she could report with uncanny precision important personal and public events that occurred—even down to the time of day. But her memory applied only to autobiographical events. She was not a particularly good student and struggled with rote memorization.
In another study, neuroscientists found that London taxi drivers had a higher density of neurons in an area of the brain called the hippocampus. The hippocampus is involved in navigation, and a higher density of neurons means more storage capacity and faster processing. This gives taxi drivers unusual abilities in solving new spatial problems requiring navigation between landmarks.
What makes AJ and taxi drivers worthy of being credited as geniuses is not what standard IQ tests measure. Rather it is their specialized, extraordinary memories.
There are many definitions of intelligence competing for attention in popular culture. But the definition that has guided my research and that applies throughout this book is a very simple one. The genius of dogs—of all animals, for that matter, including humans—has two criteria:
• A mental skill that is strong compared with others, either within your own species or in closely related species.
• The ability to spontaneously make inferences.
Animal Genius—Not All Just Song and Dance
Arctic terns have a genius for navigation. Each year they fly from the Arctic to Antarctic and back. Every five years a tern will travel the same distance it takes to get to the moon. Whales have an ingenious way of cooperating to catch fish. They create massive walls of bubbles that trap schools of fish, netting them a much heartier dinner than if they hunted alone. Honeybees have evolved a form of dance that allows them to tell other bees where to find nectar-filled flowers—it is certainly a form of genius to be able to make your living by dancing.
Genius is always relative. Certain people are considered geniuses because they are better than others at solving a specific type of problem. In animals, researchers are usually more interested in what a species as a whole is capable of, rather than each individual animal.
Even though animals cannot talk, we can pinpoint their particular genius by giving them puzzles. Animals do not need to talk to solve these puzzles, they just need to make choices. And these choices reveal their cognitive abilities. By presenting the same puzzle to different species, we can identify different types of animal genius.
Since any bird would look like a genius at navigation compared with an earthworm, it helps to compare closely related species. That way, if one species has a special ability that a close relative does not, we can not only identify their genius but also, more interestingly, ask why and how that genius exists.
For example, the spatial memory of Clark’s nutcrackers easily rivals the best taxi driver. These birds live at high altitudes in the western United States. In summer, each bird may hide up to one hundred thousand seeds throughout its territory. In winter, Clark’s nutcrackers retrieve the exact same seeds they hid nine months before, even though the seeds are covered in snow.
When compared with their corvid relatives, Clark’s nutcrackers are the champions of finding food they had hidden. A tough winter environment has made these birds into geniuses of spatial memory. However, Clark’s nutcrackers do not outperform their relatives in every memory game.
Western scrub jays are also part of the corvid family, and they also frequently hide food. However, unlike the solitary nutcrackers who rarely steal, scrub jays make a habit of it. They watch other birds hide food and later return to steal it. When tested for their ability to remember where other birds had hidden food, scrub jays proved themselves masters while nutcrackers were hopeless in the same situation. Competition has made scrub jays into geniuses of social memory. (Scrub jays do not just pilfer, they also defend against prying eyes. They prefer to hide their food in private, will re-cache their food later in a new location if another bird observes them hiding their food, and even prefer to hide food in darker locations to avoid others seeing them cache it.)
By giving different types of memory puzzles to these closely related species, scientists have been able to discern each species’s unique form of genius. By observing the problems each species encounters in the wild, scientists have also been able to understand why the two show different types of genius.
As with people, just because a species looks like a genius in one area does not mean its members are geniuses in other areas. For instance, some ant species are impressive in how they cooperate. Army ants can form living bridges over water, allowing others to cross over on their backs. Other ant species fight wars to protect workers and breeders, and some even “enslave” other ants, or keep other insects as “pets.”
But ants have one severe limitation. They are not always very flexible. Most ants are programmed to follow the scent trails of the ants ahead of them. In the tropics, you can find an “ant mill” where hundreds of thousands of ants walk in a perfect circle that resembles a crawling black hole. Ant mills have been observed up to twelve hundred feet in diameter, with a single lap taking up to two and a half hours to complete. These ant mills are also known as ant death spirals, because often the ants mindlessly follow one another in tightening circles until they exhaust themselves and die. They loyally follow the pheromones of the ants ahead of them to their death.
This leads in to the second definition of genius—the ability to make inferences. Sherlock Holmes was a genius because even if the solution to a mystery was not clearly apparent, he was always able to find it by making a series of inferences.
Humans make inferences constantly. Imagine speeding toward an intersection. Even without seeing the traffic light, you can infer the light is red when you see cars entering the intersection from the cross street.
Nature is far less predictable than traffic. Animals have to deal with unexpected surprises. For ants, following the scent of a pheromone trail is usually a foolproof method. But when the pheromone trail becomes circular, ants do not have the mental abilities to realize the trail they are following is going nowhere.
When an animal encounters a problem in the wild, they do not always have time to slowly figure out a solution through trial and error. One mistake can mean death. Hence animals need to make inferences—fast. Even when animals cannot see the correct solution, they can imagine different solutions and choose among them. This leads to a lot of flexibility. They might solve a new version of a problem they have seen before, or they might even spontaneously solve new problems they have never encountered.
Yoyo is a chimpanzee living at Ngamba Island Chimpanzee Sanctuary in Uganda. She once watched as an experimenter put a peanut through the opening of a long transparent tube. The peanut bounced when it hit the bottom. Yoyo’s fingers were too short to reach the peanut, there were no sticks around to use as a tool to reach it, and the tube was fixed and could not be turned upside down. Undaunted, Yoyo made an inference. She collected water in her mouth from the drinking fountain and spit it into the tube. The peanut floated to the top, and she happily gobbled it up. Yoyo realized she could make the peanut float, even though no water was visible when she thought of her solution. In the wild, her ability to make an inference like this could mean the difference between a good meal and starvation.
John Pilley, a retired psychology professor, adopted a Border collie named Chaser. Chaser was eight weeks old and typical of Border collies—she loved to chase and herd, she had intense visual concentration, she enjoyed being petted and praised, and she had limitless energy. Pilley had read of Rico the Border collie who knew at least two hundred German words, previously studied by Juliane Kaminski, and he was interested in seeing if there was a limit to the number of names a dog could learn. Or perhaps the memory of some of the older objects would fade as Chaser learned the names of new objects.
Chaser learned the names of one or two toys a day. Pilley, known as “Pop,” would hold up the toy and say, “Chaser, this is . . . Pop hide. Chaser find . . .” Pilley did not use food to motivate Chaser. Instead, he used praise, hugs, and play as rewards for finding the right toy.
Over three years, Chaser learned the names of more than 800 stuffed toys, 116 balls, 26 Frisbees, and more than 100 plastic objects. There were no duplicates, and all the objects differed in size, weight, texture, design, and material. In total, Chaser learned the names of more than 1,000 objects. She was tested every day, and just to be sure she was not “cheating” by getting hints from anyone, every month she had to complete a blind test in which she fetched objects in a different room, out of sight of Pilley and her trainers.
Even after Chaser had learned more than a thousand words, there was no decrease in the rate at which she learned new ones. More impressive still, the objects were organized in a variety of categories in her mind. Although the objects came in different shapes and sizes, Chaser, without any training, could distinguish between objects that were her toys and those that were non-toys.
We will discuss these studies in greater detail in Chapter 6, but for now, suffice it to say that Rico and Chaser seemed to be learning words in a similar way to human infants—they inferred that a new word belongs to a new toy. Rico and Chaser knew the new word could not refer to their familiar toys, since they already had names. This left a toy without a name as the only possible answer.
This process of making inferences is critical in understanding how dogs think. In an experimental game, dogs were shown two cups. One of them hid a toy, and the dogs were given one chance to find it. When the experimenter showed the cup where the toy was not hidden, some dogs spontaneously inferred the toy must be in the other cup. In the right situation, many dogs can make this kind of inference.
First, we look for genius in animals by comparing one species to another. Often, the challenges different species face in the wild have provided them with different kinds of genius. Some dance, some navigate, and some have figured out how to have diplomatic relations with other species. Second, we look for genius in animals by testing their flexibility to solve new problems by making inferences.
Genius in Dogs—The Breakthrough
Until recently, science had not taken the genius of dogs very seriously. The abilities of dogs like Chaser and Rico to learn new words could have been discovered as early as 1928. In that year, C. J. Warden and L. H. Warner reported on a German shepherd named Fellow. Fellow was something of a movie star; his most memorable scene was saving a child from drowning in the movie Chief of the Pack.
Much like Rico’s owner, who got in contact with my colleague Juliane Kaminski, Fellow’s owner contacted the scientists and reported that Fellow had learned almost four hundred words, noting that Fellow “understands these words in much the same manner as a child under the same circumstances would.” He had raised Fellow almost from birth and talked to Fellow the way you would to a child.
Warden and Warner went to examine the dog. They had his owner give commands to Fellow from the bathroom, so he would not unwittingly give Fellow any extra cues unconsciously. They found that Fellow knew at least sixty-eight commands (some of them helpful to a canine movie star), such as “speak,” “stand close to the lady,” “take a walk around the room.” Others were more impressive, such as “go into the other room and get my gloves.”
The scientists concluded that although Fellow had nowhere near the abilities of a child, more research was needed to understand this type of intelligence in dogs. Unfortunately, their call was not answered until Juliane Kaminski undertook her research on Rico in 2004.
In the intervening seventy-five years, dogs were largely ignored. When scientists began studying animal cognition in the seventies, they were more interested in our primate relatives. Eventually, enthusiasm extended to other animals, from dolphins to crows. Dogs were mostly left out of the equation because they were domesticated. Domesticated animals were seen as artificial products of human breeding. Domestication supposedly dulled an animal’s intelligence because they had lost the skills and intelligence needed to survive in the wild. Only two research projects were conducted to evaluate dog intelligence between 1950 and 1995, and both found dogs to be unremarkable.
Then in 1995, I did an experiment with my dog in my parents’ garage and started something new. I discovered that instead of domestication making our best friends stupid, our relationship with dogs gave them an extraordinary kind of intelligence. Almost simultaneously on the other side of the world, Ádám Miklósi conducted a similar study and independently came to the same conclusion.
These studies caused an explosion in the field of dog cognition. All of a sudden, people from all sorts of disciplines realized what had been under our noses the whole time—dogs are one of the most important species we can study. Not because they have become soft and complacent compared with their wild cousins, but because they were smart enough to come in from the cold and become part of the family.
Perhaps the biggest biological mystery of all is the origin of our unlikely relationship with dogs. Every human culture on every continent for thousands of years has included dogs, from dingoes in Australia to Basenjis in Africa. Our new understanding of dog genius has provided answers for some big questions about our best friends. How, when, and why did this powerful relationship begin? And what does it mean when we think about the origins of our own species? And just as importantly, what does it mean for your relationship with your dog?
For the first time, we can hope to answer these questions. To begin our journey, and to understand how this relationship came to exist at all, we must travel back millions of years to a time long before dogs existed. Before wolves and humans had even met.
Wolves conquer the world, only to lose it all
The best archaeological and genetic evidence suggests that dogs began evolving from wolves somewhere between twelve and forty thousand years ago. We take our relationship with dogs for granted, although on closer inspection, it is an astounding thing to have happened. People have proposed that our ancestors adopted wolf puppies, which then became domestic dogs over time. Or that wolves and humans began to hunt together. But neither of these theories really makes sense.
Wolves and humans have never had a particularly amicable relationship, although the animosity is overwhelmingly one-sided. Occasionally, there is a story of children who were adopted and raised by wolves with a happy ending, like Romulus and Remus, who went on to found Rome, or Mowgli in Rudyard Kipling’s Jungle Book. But for the most part, no other animal has been portrayed so ubiquitously as the Bad Guy throughout history.
The Bible portrayed the wolf as a ravenous destroyer of innocence. In Icelandic mythology, two wolves swallowed the moon and the sun. The Old German word for wolf, warg, also means “murderer,” “strangler,” and “evil spirit.” Those officially pronounced wargs were cast out from society and forced to live in the wilderness. Some think this is where the myth of werewolves came from, since the outcast was no longer thought to be human. As children, we grew up with Little Red Riding Hood and the Three Little Pigs, where wolves were cunning villains to be outsmarted and slain.
The revilement of wolves was not limited to myths and fables. Almost every human culture in the world that has come into contact with wolves has persecuted them at one time or another, and these persecutions have often led to their local annihilation.
The first written record of a wolf extermination was in the sixth century BC, when lawmaker and poet Solon of Athens offered a bounty for every wolf killed. This was the beginning of a long, systematic massacre that turned the wolf from one of the most successful and widespread predators in the world to one listed by the International Union for Conservation of Nature (IUCN) as vulnerable to extinction in 1982. (The gray wolf’s status had been upgraded by 2004 to a species of “least concern.”)
The Japanese used to worship wolves and prayed to them to protect their crops from wild boar and deer. When Japan ended three centuries of self-imposed isolation from the rest of the world in 1868, Westerners arrived and advised the Japanese to poison all the wolves to protect their livestock. In 1905, three men brought a wolf carcass to sell to an American collector of exotic animals. The wolf had been killed while chasing deer near a log pile. The collector paid the men for the wolf, skinned it, and sent the pelt to London. This was the last wolf in Japan.
In England, the last wolf was killed in the sixteenth century under the order of Henry VII. In Scotland, the forested landscape made wolves more difficult to kill. In response, the Scots burned the forests. Emperor Charlemagne of France organized an order of knights called the louveterie, who were essentially wolf hunters. The last wolf in France was seen in 1934. The wolf was hunted from 80 percent of China and India, and numbers have been dramatically reduced in Mongolia.
Wolves in the United States fared little better. Wolves were revered and respected in some Native American tribes, but this reverence did not protect them from being hunted and trapped for fur. The first European settlers brought their prejudices with them, and the war on wolves was swift and thorough. Soon after the first livestock arrived in Virginia in 1609, a bounty was put on wolves. Barely a century later, thanks to traps, strychnine poisoning, and the fur trade, wolves were gone from New England.
In 1915, the eradication of wolves became government business, and officials were appointed whose sole purpose was the elimination of wolves in the continental United States. They did their job well. By the thirties, there was not a wolf left in the forty-eight contiguous states of America.
Since then, wolves have been reintroduced into Yellowstone National Park and Idaho, though residents in the surrounding communities have successfully lobbied to have them hunted, since wolves occasionally kill livestock.
If this is a snapshot of our behavior toward wolves over the centuries, it presents a perplexing problem—how was this feared and hated creature tolerated by humans long enough to evolve into the domestic dog?
Domestication requires genetic change over many generations, and the early progenitors of dogs looked very much like wolves—the same animals humans have hunted and persecuted throughout the centuries. When did humans and wolves meet for the first time? And what happened to convince humans that an animal we traditionally feared and despised would make a good pet?
To answer these questions, we have to go back to the very beginning.
Life in a Freezer
Around six million years ago, the earth began to cool. Ice sheets formed on Antarctica and Greenland, and began to build up on North America and northern Europe.
In East Africa, some forest-dwelling primates left the trees for more open grasslands. They began evolving to walk upright, which caused myriad changes to their anatomy. They tamed fire, hunted and were hunted in turn, and over millions of years became the face you see in the mirror.
At the same time as our ancestors were coming down from the trees, the first canids appear in the fossil record on the other side of the world in North America. Canis ferox was about the size of a small coyote, with a more robust build and a large head.
Aliens visiting the planet six million years ago who happened to observe these two different creatures from their spaceship would not have guessed how closely their paths would intertwine. If you had to choose two species who would share a bond rivaling any other on earth, you might choose two who shared a longer evolutionary history, who were similar in size, had similar anatomy, even came from the same place. Would you have made the connection between our ancestors standing unsteadily on two feet in the cradle of Africa and a small fanged carnivore on the other side of the world? It was definitely a long shot.
Then, two and a half million years ago, increasing ice sheets, movement of the tectonic plates, and slight changes in the earth’s orbit around the sun caused the Ice Age. In less than two hundred thousand years, the world’s climate plunged from warm and temperate to freezing. Massive ice sheets as high as 1.2 miles covered North America, then collapsed into the ocean, only to form again. Gigantic icebergs filled the North Atlantic, causing temperatures to plunge even further. The formation of the land bridge between the South and North American continents cut off the Atlantic Ocean from the Pacific, and the Arctic and Antarctic waters kept the Atlantic cool and isolated from warmer equatorial currents.
The harsh conditions were interspersed with warm periods, called interglacials, when the climate was much like it is today. A glacial–interglacial cycle lasted around forty thousand years, with variations in between. But at its worst, the Ice Age was not an easy time to live. Forests were destroyed under the ice. The ground was completely frozen, except for a few surface feet that melted every summer then cracked and refroze in the winter. Half the vegetation disappeared. Glaciers cut huge pathways, transforming the landscape and diverting rivers. In addition to the bitter cold, the air was dry and full of dust. Animals and plants retreated from advancing ice sheets toward the equator; then, during interglacial periods, they returned to reoccupy their former habitats.
Between 1.7 and 1.9 million years ago, in this inhospitable environment, a wolf arrived on the scene. Canis etruscus, or the Etruscan wolf, was probably the ancestor to modern wolves. Previously, canids were isolated in North America, but the uplift of tectonic plates revealed the Beringian land bridge connecting North America to Asia, and canids quickly crossed into Asia, then spread to Europe and Africa.
The Etruscan wolf was smaller than modern wolves, with a slender build and a skull similar to the American coyote. What is impressive is that this relatively small wolf spread throughout Europe in a conquest so complete, it became known as the Wolf Event.
There were other predators at the time. Pachycrocuta brevirostris was the largest hyena ever recorded on earth. The size of a modern lion, this hyena was the only predator at the time capable of crunching bone with its massive cheek teeth in a powerful skull. But at a quarter of the size of the giant hyena, the Etruscan wolf not only competed with the hyena but went on to become the most successful predator of its time, foreshadowing the success of its descendants.
While the wolves were conquering Europe, early humans were leaving Africa for the first time. Homo erectus had large brains and fast-moving limbs and were just beginning to make complex tools. Standing around six feet, they were a good two feet taller than their australopithecine ancestors, and their long, gangly legs carried them over the Levantine corridor into Eurasia.
At the archaeological site of Dmanisi in Georgia, beneath the ruins of a medieval fortress, paleontologists found the remains of our ancestors Homo erectus. They also found an almost perfect skull of the Etruscan wolf. Which means it was probably around this time, 1.75 million years ago, that humans and wolves met for the first time.
One million years ago, the Ice Age intensified. Temperatures were erratic, and our ancestors could witness climate change from temperate to freezing within their lifetime. At the more extreme end of the cold period, a giant ice sheet stretched five million square miles, covering the northern part of America from the Atlantic to the Pacific Oceans, reaching all the way down to New York. More ice sheets covered much of northern Europe, extending from Norway to Russia and from Siberia to northeast Asia. In the Southern Hemisphere, ice covered Patagonia, South Africa, southern Australia, New Zealand, and of course Antarctica.
It was on these giant ice sheets, beneath the shadow of the glaciers, that the Ice Age beasts evolved. Mammals tend to get bigger when it gets cold. Larger animals have a lower surface-area-to-volume ratio, so they radiate less body heat than smaller animals and can stay warmer in colder climates. The second reason mammals get bigger when the climate gets cold is that as the earth cools, it gets drier. Water gets locked up in the ice sheets, and the air cannot hold as much water. This kind of climate is ideal for grasslands. But as the rainfall goes down and the grasslands get drier, the quality of the grass also decreases. Larger herbivores have larger guts that can process low-quality food; they can also roam farther, mowing down vast amounts of vegetation. As an example, a woolly mammoth could spend twenty hours a day grazing up to four hundred pounds of grass.
As the herbivores get bigger, it takes bigger carnivores to bring them down. In Europe half a million years ago, you would have recognized some of the carnivore guild, although you would have been surprised to see them in Europe and probably would have been shocked by their size. The lion (Panthera leo) is the same species as the African lion, but 50 percent larger. The hyena (Crocuta crocuta) was around 25 percent larger than modern hyenas. Weighing around half a ton, the cave bear was the largest bear around and was completely herbivorous, although it competed for den space with predators.
Some members of the carnivore guild stayed the same size. The leopard, Panthera pardus, was around the same size it is today in Africa, while wolves were about the same size as the larger modern-day Alaskan wolves.
Then there were species you would not see today. The saber-toothed cat (Smilodon fatalis) was the size of modern lions. From the sheer numbers in fossil deposits in the Californian Rancho La Brea Tar Pits (they were five times more common than the next predator down), the saber-toothed cats were the top predators at the time. They gripped their prey with powerful front limbs, using retractable claws to drag the prey toward them. Their upper canines were long and curved and could puncture the neck of their prey with a single lethal stab. They hunted in prides and were capable of bringing down prey much larger than themselves.
Neanderthals—Wild Dogs of the Ice Age
Another member of the carnivore guild was the Neanderthals. These were the Europeans who evolved from the first immigration of early humans from Africa. Their forebears appeared in Europe around 800,000 years ago, and the peak of the Neanderthals began 127,000 years ago. These big, barrel-chested humans had short forelimbs and robust fingers and toes to help them conserve heat and avoid frostbite. They had a football-shaped head with a heavy browridge and a large lower jaw with a receding chin, giving them an ape-like appearance. Their large, flat noses with massive nostrils probably had an excellent sense of smell and may have warmed the chilling air of the Ice Age before it reached their lungs. They had strong muscled bodies built for carrying heavy loads, but the alignment of their hips shows they probably walked less efficiently than modern humans.
Neanderthals survived the cruelest years of the Ice Age. They hunted woolly mammoths and other large herbivores, and their stone tools allowed them to quickly tear off flesh (similar to wild dogs) and—if they had enough time before the larger scavengers arrived—crack open bones for nutritious marrow, like hyenas.
So this was the Ice Age bestiary. It must have been an awesome sight, the herds of woolly mammoths grazing the tundra, saber-toothed cats lying in wait, and giant hyenas scavenging over a kill. These enormous creatures must have seemed timeless, invincible even.
Then the arrival of a new predator changed everything. Modern humans arrived in Europe around forty-three thousand years ago, and within fifteen thousand years, Neanderthals and almost all the large carnivores went extinct.
There is a lot of argument about what caused this mass extinction at the end of the Pleistocene, particularly of the Neanderthals. Humans have always outcompeted other animals, but it is curious that they drove a close relative to extinction. Far from being the thuggish brutes portrayed in movies, Neanderthals had even bigger brains than modern humans. They had culture, perhaps language. Although new genetic evidence suggests most European descendants have Neanderthal genes in them, pointing to crossbreeding at one time or another, the larger Neanderthal population definitely went extinct.
Some say it was climate change. Others say it was direct or indirect competition with humans. Steve Churchill, from Duke University, argues that Neanderthals were vulnerable to extinction before modern humans arrived. First, their populations were already thinning in Europe. Their big, squat bodies were good for keeping warm, but they required a lot of calories to maintain, which did not leave a lot left over for investing in reproduction and child care. Most Neanderthals died between their twentieth and thirtieth birthdays, and Neanderthal bones reveal diseases attributable to malnutrition, such as rickets and osteoarthritis. Thomas Berger, formerly at the University of New Mexico, found that bone traumas in Neanderthals and modern-day rodeo riders were similar, especially in the head and neck areas. Although Neanderthals did not ride bucking horses, they did come into a lot of unfriendly contact with large mammals.
Second, according to Churchill, Neanderthals’ diet was mostly meat, which means they were competing with other predators in the carnivore guild, and Neanderthals were not top predators. To be a top predator, you need two things: You have to be big to overpower your competitors, and you have to be social. (For instance, leopards are large but they are not top predators because they are solitary.)
Neanderthals were neither. Though they were robust, they certainly could not compete with lions, saber-toothed cats, or even leopards. And since Neanderthals lived in groups of only fifteen or so, their numbers were not big enough to overpower these predators. Churchill argues that in the predator hierarchy, Neanderthals were probably around the level of a pack of African wild dogs (Lycaon pictus) still living on the African savanna today. If they managed to bring down large prey, they had to quickly strip off as much high-quality meat as they could before they were chased off by other predators. Otherwise, they were left scavenging the remnants of other kills.
The consequences of being middle to low ranking are quite severe. The socially dominant carnivores ate as much as 60 percent of all the herbivores killed by predators. This means that the rest of the carnivore guild had to split up the other 40 percent. But this split was not even. The next most dominant carnivore got the majority of this 40 percent, then the next dominant species received the biggest share of what remained, and so on. So even though Neanderthals may have been skilled hunters, they still would have struggled to obtain enough meat to survive.
The New Gang in Town
Churchill points out that when modern humans arrived in Europe, they were the socially dominant carnivore. Although not able to compete with other carnivores in terms of strength, they came in large numbers. They also had something the Neanderthals did not—projectile weapons, such as spear throwers and perhaps even bows and arrows. Neanderthals had spears, but these spears were close-range weapons. If there was a group of lions or saber-toothed cats on a kill, a small group of Neanderthal males with spears would not have a chance. But large groups of humans who could launch spears from forty to fifty meters away, this was competition.
After modern humans muscled out the carnivores, they fed on the herbivores; woolly mammoths, woolly rhinos, horses, bison, oryx, wild cattle, and red deer. As the modern human population density increased, they started competing for food like fish, birds, rabbits, and squirrels with smaller carnivores, like the lynx and fox, whose numbers plummeted. Later, the large herbivores followed. As a result, fifteen thousand years after modern humans arrived, most of the larger members of the carnivore guild, including Neanderthals, were extinct.
Only two large carnivores survived—the brown bear and the wolf, Canis lupus. The omnivorous brown bear fed on vegetation, fish, and small mammals and perhaps avoided direct competition with humans. Though they did not go extinct, their numbers certainly went down.
The survival of Canis lupus is inexplicable. They appear in the fossil record around a million years ago in Alaska, and they arrived in Europe approximately half a million years ago.
Not only did wolves survive to spread throughout most of the Northern Hemisphere and become one of the most successful predators in the world, but somewhere along the line, a subpopulation of wolves spent enough time with humans over many generations that their morphology, physiology, and psychology changed from wild wolves to domesticated dogs.
The theory has long been that humans intentionally adopted wolf puppies and tamed them on purpose. The late zoologist Ian McTaggart-Cowan wrote:
Somewhere in early history a young wolf was brought into the family circle of man and through the years became the source of the domestic dog and our most successful and useful experiment in domestication.
In a 1974 paper, wolf expert David Mech from the University of Minnesota says,
Evidently early humans tamed wolves and domesticated them, eventually selectively breeding them and finally developing the domestic dog (Canis familiaris) from them.
But when you think about it, this does not really make sense. Modern humans were extremely successful hunters without wolves. And wolves eat a lot of meat, as much as eleven pounds per wolf per day. A pack of ten wolves would need an entire deer each day. Starvation was a real threat for many carnivores in the Ice Age, and competition would have been fierce. So fierce that humans, who were no longer content with only 60 percent of the energy budget, drove every other large carnivore except wolves to extinction. (Starvation is a significant cause of mortality in many carnivores, including lions, spotted hyenas, wolves, wild dogs, and lynx. As a general rule, it takes about twenty-two thousand pounds of prey to support about two hundred pounds of carnivore biomass—irrespective of carnivore body size.)
Wolves are extremely possessive of their food, and if humans wanted some of the kill, they would probably have had to fight them for it. When wolves see prey run, it triggers a “rush” response, where they chase down their prey and inflict numerous bites until the prey falls. The feeding frenzy that follows is quick and intimidating. Wolves are historically plagued by scavengers, and their sharp, shearing teeth are specialized for tearing off large chunks of meat. Wolves prize the same parts of the kill as humans: high-protein internal organs like the liver, heart, and lungs, followed by the muscle. There are frequently squabbles over food, and a bite that would be relatively harmless between wolves could lead to a serious injury if inflicted on a soft-skinned human.
Other domesticated animals make sense. Cattle, pigs, and horses may all have started out wild, perhaps a little aggressive when cornered, but none of them had fangs and lived on meat. The wolf–human relationship makes no sense at all.
And yet, at an ancient site in Israel, to the east of the Mediterranean and north of the Sea of Galilee, a burial site is nestled among the hills beside a lake. Under a slab of limestone, a human skeleton rests its head on its left wrist, and the hand gently lies on another skeleton—a puppy.
Dated at between ten and twelve thousand years old, the human was a Natufian, part of a Stone Age settlement along a narrow strip parallel to the Mediterranean Sea that stretched from Turkey to the Sinai Peninsula, on whose tallest peak (Mount Sinai) some say Moses was given the Ten Commandments. It was not the barren, thorny desert it is today, but a forested woodland covered in wild foods and game. The Natufians were hunter-gatherers who settled in the region. They lived in dwellings half buried in the earth and had tools such as knives made from bone and stone grinding implements.
But more important are the burial sites. Tucked away in the heart of the Natufian landscape, each base camp contained graves, either in deserted dwellings or just outside the houses. Bodies were carefully placed, usually stretched out and facing upward. They might be decorated with headpieces, necklaces, and bracelets made from shells, beads, and teeth. Several graves had more than one body, and the Natufian sites are among the earliest records of humans being buried with another species—in this case a dog. Similarly aged burials of dogs have been uncovered across Europe, the Levant, Siberia, and East Asia.
So somewhere between the arrival of modern humans forty-three thousand years ago and the first dog burials around twelve thousand years ago, wolves became domesticated. Not only that, but the bond between humans and the domesticated wolf—now a dog—was so strong that the two were often buried together. And through the centuries, when wolves continued to be persecuted and almost driven to extinction, dogs and humans grew even closer.
As populations of hunter-gatherers became more sedentary, wolves must have started coming into frequent contact with humans, whether through hunting or scavenging around campsites, or eating garbage or human feces. But first, something had to change, something dramatic, so that humans no longer perceived the wolves as a threat.
It was by complete accident that I stumbled on the answer.
The perfect place for a scientific discovery
Like a Seattle grunge band, I got started in my parents’ garage. It was late fall in Atlanta, Georgia, and we were having a cold snap. The garage had only three walls. The wind cut through my tracksuit pants and reminded me why garages need a door. Like most garages, ours had a cement floor polka-dotted with oil stains and was full of junk. Cans of paint, toys, and camping gear lined the walls. Dad had strapped an old Mad River canoe to the ceiling so haphazardly, I was convinced it would fall any minute.
Sitting to one side was my best friend, Oreo. My parents got Oreo from a neighbor. As a die-hard Georgia Tech fan, Dad liked the idea that our new puppy’s Labrador parents were named GT and Jacket. He hoped I would name the puppy Buzz, after Georgia Tech’s yellow- jacket mascot. Since I was seven, I named him after my favorite food, Oreo cookies.
There was a fence around our suburban yard, but it was little more than a symbolic barrier. Oreo could open the gate latch if we forgot to lock it, and there was a corner of the fence low enough for him to jump over. Oreo was always roaming around, getting into trouble. My mother would get the occasional phone call because Oreo had invited himself to a neighborhood pool party and was splashing around with the kids. Or while driving home, we would find a neighbor trapped behind his lawn mower because Oreo was endlessly plopping tennis balls in front of it to force a game of fetch.
But Oreo only got into trouble when I was not around. He preferred hanging out with me to anything else. We rambled through the woods, swam in neighborhood lakes, and visited my friends and their dogs. Oreo was so loyal that when I rode my bike to a friend’s house for a sleepover, Oreo would sit on the doorstep until we went home the next morning.
I was as obsessed with baseball as Oreo was with me. We were a match made in Cooperstown. I could take a bag of baseballs, hit each one, and wait till Oreo brought them back so I could do it all again. Or I would take aim at something in the yard, and whether I hit or missed, Oreo brought back the ball so I could keep pitching. I knew at ten that my career as a starting pitcher for the Atlanta Braves would be thanks to Oreo. He never let me quit. If I put away the balls, he would conjure another one from the yard, drop it on my feet, and bark until I was ready to go again. The one hitch was that any ball that entered Oreo’s mouth became a drool sponge. By about the tenth throw, the ball would be twice its original weight, with a slobber tail like a comet. Oreo probably never understood why no one was as excited to play ball with him as I was.
To Be or Not to Be Human
Fast-forward ten years. I made the first cut of the college baseball team but then gave it up. A professor at Emory University introduced me to something that captured my imagination more than winning the seventh game of the World Series. Mike Tomasello was trying to figure out what makes us human. As a nineteen-year-old, I had never given much thought to such a profound question, and I was in awe that anyone could even attempt to answer it.
There is no doubt that our species has a special kind of genius. Our powers are not always used for good. But they are impressive. We have managed to colonize every corner of the earth, molding glaciers and deserts into comfortable living quarters. We are the most successful large mammals on the planet in terms of our population size and the influence we have on the environment. Our technology can preserve or destroy life. We can fly above the earth’s atmosphere and trawl the deepest trenches of the ocean. As I write, Voyager 1 is more than eleven billion miles from our planet, sending NASA signals from the edge of our solar system.
It was not always like this. A few million years ago, we were indistinguishable from other forest-dwelling apes. Fifty thousand years ago, we were dodging the fangs of saber-toothed cats and giant hyenas. Twenty thousand years ago we had no governments or even permanent housing. Today, we cannot imagine surviving without the Internet or iPads. What happened to us after our ancestors’ split from the last ancestor we shared with other apes? What was the first change that led to all the other changes? How did it all happen?
Until I met Mike, I had not realized that to understand what it is to be human, you had to figure out what it is not to be human. My new vocation was studying the minds of other animals to better understand ourselves. Likewise, as a famous psychologist studying the development of infants, Mike compared infants with chimpanzees to test ideas about what makes us unique. He never guessed that he was destined to become a dog researcher.
It was Oreo who led Mike and me to our destinations, but it was Mike’s knowledge of infants that led us to Oreo. The theory and methods for studying infant psychology allowed for the revolution in our understanding of dogs.
Humans are not born with adult cognitive abilities. Our infants are born helpless and require the greatest amount of parental care of any animal. This is mostly due to babies’ underdeveloped brains. At birth, our brains are only a quarter of their adult size. This is because the human pelvis is designed for walking upright, which has resulted in a small pelvic aperture relative to bonobos and chimpanzees. The aperture is so small that only underdeveloped brains can fit through it during birth. This means most of our brain growth must occur after our birth.
Studies in cognitive development have revealed that not all skills develop at the same time and rate in infants. Early skills become the foundation for more complex skills.
Mike was one of the first to realize that infants develop powerful social skills as early as nine months old. This nine-month revolution allows infants to escape an egocentric view of the world. Infants begin paying attention to what others are looking at, what others are touching, and how others react to different situations. If Mom looks at a car, infants begin following her gaze by matching their line of sight to hers. If infants see something strange like an electronic singing Santa, before they react, they look to an adult’s face to gauge their reaction.
Almost simultaneously, infants begin to understand what adults are trying to communicate when they point. Infants also begin pointing out things to other people. Whether infants watch you point to a bird or point to their favorite toy, they are beginning to build core communication skills. By paying attention to the reactions and gestures of other people, as well as to what other people are paying attention to, infants are beginning to read other people’s intentions.
Intention reading provides a cognitive foundation for all human forms of culture and communication. Shortly after the nine-month revolution, infants begin to imitate the behavior of others and acquire their first words. Intention reading allows infants to accumulate cultural knowledge that would be impossible for them to obtain on their own. Infants who show delayed development of intention reading usually have problems learning language, imitating, and interacting with other people. Without culture and language, we could not build on the accomplishments of previous generations. There would be no laws, rockets, or iPads. We would probably have ended up as easy targets for all sorts of predators.
Standing on a beach in Australia, I saw a large black fin come out of the water near a group of swimmers. Over the noise of the waves, it was impossible for them to hear me. I waved frantically at the swimmers, and when I had their attention, I did something I had never done before—I bent over and placed my hand on my back like a fin. The swimmers hurriedly got out of the water, even though they had probably never seen anyone do this. From my simple gesture, the swimmers knew I had seen something they had not. Given the context, they were able to infer what I was trying to tell them—there was danger in the form of a shark. This social inference requires an understanding of my communicative intention. The swimmers understood my gestures as both communicative and helpful. They could then think about how they should adjust their behavior. Luckily, the fin belonged to a dolphin, but if it had been a great white shark, understanding communicative intention could have saved their lives.
Understanding communicative intention gives us unprecedented flexibility in solving problems. To find out if this is what makes us human, Mike compared humans with our closest living relatives, bonobos and chimpanzees. If we have a skill that bonobos and chimpanzees do not have, then this skill probably evolved after our lineage split from the bonobo and chimpanzee lineage between five and seven million years ago.
Mike needed to compare the abilities of bonobos and chimpanzees in understanding communicative intentions to infants’. If understanding communicative intentions is as crucial to humans as Mike thought, then bonobos and chimpanzees should not show an understanding of communicative intentions. However, if bonobos and chimpanzees were as skilled as young infants, Mike would know he was on the wrong track.
It is quite tricky to test for an understanding of communicative intention in an ape who has no language. However, while human language is the most complex form of communication, it is not the only form. Both bonobos and chimpanzees use visual gestures during social interactions. They can ask to play by pushing or slapping someone; they can ask for food by placing their hand under the chin of someone who is eating. By the time they are adults, bonobos and chimpanzees use and understand dozens of different gestures. This is similar to infants. By examining how bonobos and chimpanzees respond to the gestures of others, we can see whether they understand one another’s intentions.
Mike borrowed a game developed by Jim Anderson, a Scottish primatologist from the University of Stirling in the UK. Anderson hid food in one of two containers, then gave various primates a clue where the food was. He either touched, pointed, or looked at the container that had the food. Anderson tested capuchin monkeys, who failed miserably. To succeed, the monkeys had to be trained for hundreds of trials, and each time they got a new kind of clue, they had to be trained all over again.
Since chimpanzees are so socially sophisticated and so closely related to us, Mike thought they would do better than monkeys. But chimpanzees also failed. Even if they eventually learned they should choose the container you pointed at, if you changed the clue by standing farther back from the container while you pointed, again the chimpanzees failed.
The only exception was when the chimpanzees had been raised by humans. This meant that they had interacted with humans for thousands of hours. The few chimpanzees with this unusual rearing history were the only ones who were able to spontaneously use a variety of human gestures to find the food.
Mike seemed to have strong support for his idea that spontaneously understanding another’s intended communication was a kind of genius unique to humans. Unlike infants, chimpanzees could use new gestures in a new context only if they were given a lot of practice with the game or if they had been raised by humans. This suggested that chimpanzees do not understand that when you point, you are trying to help them. Mike thought he may have discovered what made humans unique.
My Dog Can Do That
One day in my sophomore year, I was helping Mike play these signaling games with chimpanzees. We started to discuss the implications of our findings. Mike suggested that only humans understand communicative intentions, which allows us to spontaneously and flexibly use gestures, like pointing.
I blurted out, “I think my dog can do it.”
“Sure.” Mike was amused. “Everybody’s dog can do calculus.”
During our training for the World Series, Oreo developed a special talent. He could fit three tennis balls in his mouth at the same time, sometimes four if he positioned them just right. I would throw one, and then while he was fetching the first one, I would throw the second and third in different directions. After he had fetched the first ball, Oreo would look at me, and I would point to where the second ball was. After he fetched the second ball, I would point to the third, and off he would go to find it and finally bring all three back to me in triumph, his cheeks bulging like a chipmunk who had eaten the whole bag of nuts.