Dogs Decoded

PBS Airdate: November 9, 2010

NARRATOR: We are inseparable.

WOMAN 1 (Chocolate Lab Owner): We're best friends.

DR. BRIAN HARE (Duke University): Anywhere you find humans you will almost certainly find dogs.

NARRATOR: And they are smarter than we ever imagined. Astonishing new research is revealing that dogs are far more than merely tamed wild animals.

PROFESSOR DANIEL MILLS (University of Lincoln, England): What makes our relationships so special is the dog's ability to be able to read our emotions so effectively.

NARRATOR: Have they evolved a new kind of intelligence?

DR. JULIANE KAMINSKI (Max Planck Institute, Germany): Suddenly, there were dogs doing something that not even chimps could do.

NARRATOR: Have dogs developed a language to communicate complex emotions?

DOGS BARKING: Bark , bark, ruff, ruff.

íDíM MIKLíSI: Anger, fear, happiness, despair.

MAN 3 (Pug Owner): You can almost understand what they're thinking.

NARRATOR: Why do we love an animal that was once a fearsome predator?

How did dogs go from this to this? Is it in the genes or the way we treat them? And when did it all begin?

The bones tell one story.

Peter Rowley-Conwy (Durham University, England): We start seeing the first things 12,- or 13,000 years ago.

NARRATOR: The genes tell another.

Greger Larson (Durham University, England): One-hundred-thousand years or more.

NARRATOR: The answer is more important than you might think.

Greger Larson: Without dog domestication, civilization just would not have been possible.

NARRATOR: Dogs Decoded, right now, on NOVA.

MAN 1 (Irish Wolfhound Owner): Corrie! Come here.

NARRATOR: There are more dogs than babies worldwide, nearly half a billion.

MAN 1 (Dog Owner): Good boy. Sit.

NARRATOR: We treat them as if they are fellow human beings, with all the thoughts, feelings and emotions of a family member.

MAN 2 (Dog Owner): (Dog Owner): Good girl.

NARRATOR: It's an incredibly close relationship. We share our lives, our homes, even our beds with them.

WOMAN 1: We're very close. We're best friends.

WOMAN 2 (Dog Owner): Pippin sleeps with us. He loves being in the bed with his head on the pillow.

MAN 1 : He just seems to fit in.

MAN 2: She's there with my slippers, first thing in the morning. She's part of the family; she is the family.

NARRATOR: For decades, science has dismissed dogs as being unworthy of legitimate study, But all that has changed. Scientists are now attempting to understand dogs like never before.

What kind of bond do we really have with our dogs? Can we read each other's emotions? Are they smarter than we think? And how and when did this unique relationship develop?

DR. BRIAN HARE: Dogs are all over the world; they're everywhere. Anywhere you find humans, you will almost certainly find dogs.

DANIEL MILLS: We're now beginning to realize that we can answer certain questions in dogs that we can't really answer in any other species.

JULIANE KAMINSKI: There's been this explosion in dog research, I think, really, because they are specially tuned in to humans, and this makes dogs extremely interesting as a model.

NARRATOR: Here at England's University of Lincoln, Professor Daniel Mills specializes in veterinary behavioral medicine. He is using eye tracking technology, to probe how close our relationship really is.

DANIEL MILLS: What we're trying to do here is see the world from a dog's perspective, rather than just impose our own views as to how we think the dog sees the world.

NARRATOR: He's attempting to discover if dogs are as good at reading our emotions as their owners claim.

WOMAN 1: He'll know what I'm thinking even before it's turned into a thought bubble.

WOMAN 3 (King Charles Spaniel Owner): He is clearly an animal; I accept that he is totally an animal. I am not under any illusions that he isn't, but he's more knowing than I would expect an animal to be.

WOMAN 4 (Dog Owner): He will look at me with sorrowful eyes and then give me one big lick on the hand, as if to say, "It's alright."

MAN 2: It's this sixth sense that dogs have.

DANIEL MILLS: One of the things that a lot of people comment on is that dogs seem to be naturally attuned to them and be able to sense their moods and whatever. And part of our work here is actually to look into the scientific basis of that.

NARRATOR: The key to a dog's ability to read our emotions might lie in something we all do without knowing it.

DANIEL MILLS: When we express our emotions in our faces, we don't do it symmetrically. It's been shown that, if you take somebody's face when they're expressing some emotion like happiness or anger or something like that, there is a difference between the left and right side.

NARRATOR: Composite faces consisting of two right or two left sides look very different.

DANIEL MILLS: One of the theories is that maybe our emotions are more faithfully presented in the right side of our face, and that's the side that we tune in to.

And when we look at a face, we have what's known as a natural left-gaze bias, so you naturally look much more towards the left, i.e. the right-hand side, of somebody's face.

NARRATOR: Eye-tracking software demonstrates that, when presented with a human face, we nearly always look left first. Daniel Mills wants to find out if dogs use the same trick to read human faces.

DANIEL MILLS: Shifting the direction of your gaze, we thought, was fairly unique to people, until we started looking at dogs.

ANAíS RACCA (University of Lincoln, England): Taz! Tazy!

NARRATOR: To test the theory, his team recreates this experiment with dogs.

ANAíS RACCA: Moose, what's that?

NARRATOR: They present a series of images showing human faces, dog faces and inanimate objects and record the direction of a dog's gaze with a video camera.

ANAíS RACCA: We found that dogs, when they are looking at pictures of dog faces or objects, they will look randomly on the left or the right.

NARRATOR: But, when it comes to human faces, they make a remarkable discovery.

ANAíS RACCA: So now we have Taz looking at a human face. So, first she's looking in the middle of the screen, and here is the first eye movements on the left. She's in the middle and she's going on the left.

So, now, this is Moose, and then we can see really well that this is a left gaze; from here to here. We can see the white here. She's even moving her head.

NARRATOR: Does this mean dogs can read human emotions? As far as we know, no other animal has this relationship with the human face. And dogs don't do this with each other. This suggests that dogs have acquired a new skill enabling them to communicate with us on an emotional level.

DANIEL MILLS: Being able to detect when somebody is angry or potentially going to be harmful to them, you could understand that there may be a biological advantage in being able to read people's emotions and, equally, that it makes sense for a dog to approach somebody when they're smiling.

If dogs can read human emotion, and increasingly the scientific evidence is beginning to point in that direction, that's going to form the basis of a very powerful bond between human and dog.

NARRATOR: Evidence like this appears to underpin our conviction that dogs understand us in a way that other animals cannot.

But for many dog owners, this unique relationship is much more than a one-way street.

WOMAN 2: Well, I like to think we can understand him.

YOUNG GIRL 1: Yes, but he woofs and we talk.

WOMAN 2: That's because he wants to be part of the conversation.

WOMAN 4: If he's bored, he'll take a deep sigh and go, (imitates dog).

WOMAN 2: I think he's got a bark when he wants to go out, and I think he's got a bark when he hears strange noises.

WOMAN 4: Sometimes, when he tells the kittens off, he goes, (imitates dog), like that.

MAN 3 (Pug Owner): If you're in a certain mindset, you can almost understand what they're thinking.

NARRATOR: The idea that we can understand barking, almost like a language, has always been dismissed by scientists.

But, in Hungary, an experiment is underway, looking for evidence to back up the claims made by dog owners. Here in Budapest is one of the world's first research facilities dedicated to investigating the human/dog relationship. Dr íDíM MIKLíSI wants to see if humans really can understand dogs' barks.

Today, he's out on a field expedition, collecting recordings.

DR. íDíM MIKLíSI (Eí¶tví¶s Lorí¡nd University, Hungary): Scientists used to think that barking is a random noise without any specific information or content. However, we have a different idea. Dogs might tell us something about anger, fear, happiness, despair. So these are basic emotions which I think humans might be able to recognize in the barking sound.

NARRATOR: To test this idea, Adam and his team act out a number of scenarios, provoking dogs to bark in different ways.

When other people listen to these recordings, will they be able to match the bark to the emotion?

íDíM MIKLíSI: Alone bark.

MAN 2: That sounds like a dog asking for attention.

FEMALE RESEARCH PARTICIPANT 1: It's anxious.

WOMAN 3: It's sad; distressed.

MAN 4: Wants to be let off a chain or something like that.

FEMALE RESEARCH PARTICIPANT 2: I think that one's playful.

WOMAN 2: Excitement.

MAN 2: It seems as though they're actually asking their owner for something.

WOMAN 4: It sounds as if it may want a ball or a toy or something. She could be playing with it.

YOUNG GIRL 1: Angry.

WOMAN 4: This is a sound that she would make if she saw somebody behind the fence walking along.

FEMALE RESEARCH PARTICIPANT 1: It's a stranger, I think. It's a stranger encroaching on her territory.

NARRATOR: The results of Miklí³si's research are remarkable. It demonstrates a strong agreement between people about the meaning of different barks.

íDíM MIKLíSI: Overall, in the study, you could see that people can discriminate six barks, and most of them were quite successful in this.

NARRATOR: Dr. Miklí³si has created a system to analyze the barks. It's helping him decode how dogs communicate meaning.

íDíM MIKLíSI: I measured the three features of this sound. One was the frequency, the other was the tonality, and the third was the interval between the barking sounds. And, probably, this is also what the judgment of people is based on when they are describing the bark in terms of emotional content.

NARRATOR: But what's more surprising is not our ability to interpret the barks, but what the barks reveal about dogs.

In the natural world, dogs' wild relatives, wolves, only bark as a warning. Amazingly, during the course of domestication, dogs may have evolved their elaborate vocal repertoire especially to communicate with us.

íDíM MIKLíSI: At the basic level, everyone can do it, and there is a good chance that barking is a very good means to communicate with humans.

NARRATOR: The evidence from these recent experiments seems to confirm what dog owners have asserted all along, that dogs and people are incredibly attuned to each other, in a way that no other two species are.

And new research techniques now allow us to study, more precisely, the nature of this bond.

Some scientists believe that our interaction has a biochemical signature that may be similar to what happens between a mother and baby.

MOTHER OF NEWBORN: It's really hard to describe. It's just an amazing feeling.

NARRATOR: In Sweden, Professor Kerstin Uvnas-Moberg has been studying the role of the hormone oxytocin in creating the bond between mothers and their newborns.

KERSTIN UVNíS-MOBERG (Karolinska Institutet, Sweden): Oxytocin is a little, little peptide hormone. It's just nine amino acids. It's produced in a very old part of the brain, called the hypothalamus. And oxytocin helps the mother quickly establish the positive feelings and the bond to the baby.

NARRATOR: Each time a mother breastfeeds, she has a new release of oxytocin which may reinforce the bond.

KERSTIN UVNíS-MOBERG: It's sort of, in a way, difficult to understand how you can be familiar with somebody who is actually a stranger so quickly, don't you think?

MOTHER OF NEWBORN: Yes.

NARRATOR: Professor Uvnäs-Moberg believes oxytocin plays a similar role in the bond between dogs and their owners.

To test the theory, blood samples are taken from dogs and their owners before and during a petting session.

KERSTIN UVNíS-MOBERG: We had a basal blood sample, and there was nothing, and then we had the sample taken at one minute and three minutes, and you could see this beautiful peak of oxytocin. The fascinating thing is, actually, that the peak of oxytocin is similar to the one we see in breastfeeding mothers.

NARRATOR: Surprisingly, it's not just the owners who are affected. Blood samples taken from dogs reveal a similar burst of oxytocin.

KERSTIN UVNíS-MOBERG: It is a mutual kind of interaction, you know. The owner touches with her hands, and they both smell, hear and see each other. That is a very nice way of triggering oxytocin release in the two of them.

NARRATOR: Oxytocin has a powerful physiological effect. It can lower the heart rate and blood pressure and may lead to reduced levels of stress. Research indicates that owning a dog could even extend your life.

KERSTIN UVNíS-MOBERG: If you have a dog, you are much less likely to have a heart attack, and if you have a heart attack, you are three to four times more likely to survive it if you have a dog than if you don't.

NARRATOR: Our relationship with dogs goes back thousands of years. So how did it begin? Where did the first dog come from?

Darwin recognized our unique relationship with dogs, but even he couldn't say for sure which animal was the true ancestor of today's dogs.

It's a complex puzzle that both archaeologists and geneticists are working to solve.

Peter Rowley-Conwy: There's a huge amount of variation in present day dogs. Consider the difference between a Pekingese and a Great Dane. Could they really all be descended from one wild ancestor?

Greger Larson: It could have been a coyote that might have introgressed with a wolf, and then that may have been slightly selected upon to create one particular breed of dog, or jackals or African wild dogs. Any number of these other dog-like species that are out there must have somehow come together, and that's where that variation must have come.

NARRATOR: Until the advent of genetics, archaeology had few firm answers.

GREGER LARSON: All you have to play with are the bones. And so, when you look at the bones, if you don't have a very small flat-faced, round-headed pug in the archaeological record, you don't know where that came from.

Those are questions that, before genetics, you really couldn't answer.

NARRATOR: To unravel the evolutionary origins of dogs, geneticists compare D.N.A. from dogs with that of their wild relatives. Specifically, they look at mitochondrial D.N.A. sequences which pass, unchanged, down the maternal line. Since mitochondrial D.N.A. changes little over time, it can act as a kind of signature left by an animal's ancestors.

GREGER LARSON: Those markers, in domestic dogs, show them to be much more closely related to grey wolves than they are to any other species. There's no admixture, so we never see a mitochondrial signature of, say, an African wild dog or jackal or coyote in a domestic dog. And of the thousands upon thousands of mitochondrial D.N.A. that has been extracted from domestic dogs, every single one of them just looks just like a grey wolf.

NARRATOR: This controversy is settled; dogs are domesticated wolves. But a mystery remains: when and how did this change take place?

PETER ROWLEY-CONWY: What is clearly a dog? Clearly, a dog is something which is clearly not a wolf.

Well, here's a wolf skull, and, as you can see, it's a long quite low skull with a relatively flat top. The teeth are quite large and the thing is quite narrow.

Compare that with a domestic dog. This is a cairn terrier, and, as you can see, the process of domestication has gone really quite a long way. The whole face is very much shorter; it's been contracted towards the brain case. The brain case itself has a much steeper front and a much more bowed upper surface, so if you found that, you would be in no doubt you were dealing with a domestic dog.

But this is a domestic Alsatian, and telling these apart, really, would be substantially difficult.

NARRATOR: And since early dogs were probably very wolf-like, it's hard to pinpoint when domestication happened, by looking at the shape of the bones.

PETER ROWLEY-CONWY: The best I can give you is around 12-, or 13,000 years ago. We start seeing the first things that everybody would accept as being domestic dogs.

NARRATOR: But mitochondrial DNA offers a different set of clues.

GREGER LARSON: The original genetic dates that were coming out seemed to suggest that domestication was happening on a far earlier timescale than was suggested by anything in the archaeological record. The first dates that were coming out were on the order of a hundred-thousand years or more, which a lot of archaeologists raised their eyebrows at.

NARRATOR: It's hotly debated exactly when dogs were domesticated, but geneticists and archeologists agree on one thing: our relationship with dogs goes back thousands of years further than with any other pet.

It was a time when we were still hunter-gatherers.

PETER ROWLEY-CONWY: Dogs were certainly the first animal to be domesticated, and they fit into hunting and gathering societies probably better than any other species out there.

GREGER LARSON: At this stage, when we're hunting and gathering and killing wild animals, after you finish with them, you're creating a relatively large pile of bone and leftover meat, things that these wolves would have been very attracted to. Those wolves that were able to take advantage of that resource and were a little bit less afraid and could approach the human camp were then setting themselves up into a closer relationship with humans.

PETER ROWLEY-CONWY: We are carnivores; we are social carnivores. We hunt in groups, and we hunt in daylight. There are not many other species that do that. The wolf is a social carnivore that hunts by daylight, and, therefore, I think there's natural potential for teamwork between those two species.

GREGER LARSON: We became much better hunters with dogs. We are more successfully taking down large game, which means we have more food to eat, which means we can have more offspring, which means the overall populations of humans grow.

NARRATOR: Dog domestication may have helped pave the way for a fundamental change in human lifestyle.

PETER ROWLEY-CONWY: It's hard to see how early herders would have moved and protected and guarded their flocks without domestic dogs being in place. And one has to wonder whether agriculture would ever really have made it as a viable alternative to hunting and gathering.

NARRATOR: Some believe that the influence of dogs on our development was not just important but pivotal.

GREGER LARSON: Dogs absolutely turn the tables. Without dogs, humans would still be hunter gatherers, and without that initial starting phase of dog domestication, civilization just would not have been possible.

NARRATOR: We look at our dogs and we see an intelligence, an ability to interact with us, unlike any other domesticated animal. But are dogs really that clever, or are they just dumb animals taught to perform tricks that mimic human behavior?

FEMALE RESEARCH PARTICIPANT 1 (Mutt Owner): I think she is very smart. She learns tricks fairly quickly.

MAN 3: If I am packing a suitcase they will go and sit in the suitcase because they know that suitcase is going to go somewhere.

WOMAN 4: When I'm talking to him, most of the time, his little head usually jilts to the side, as if he knows what I'm saying.

MAN 2: I do talk to her, and she picks up on what I say to her. I know it sounds stupid, but I do actually have a conversation with my dog.

NARRATOR: So how does the intelligence of a dog compare in the animal kingdom? New research is discovering that, in certain ways, dogs may actually think more like us than any other animal, including our nearest relative, the chimpanzee.

JULIANE KAMINSKI: Of all the questions around the evolution of human cognition, of course people would focus in on chimps, quite naturally, and suddenly there were dogs doing something that not even chimps could do.

NARRATOR: Cognitive psychologist Juliane Kaminski compares chimps with dogs, in a series of revealing experiments. At Leipzig Zoo, Kaminski is testing chimps to see if they can understand human gestures, like pointing, to find a hidden treat.

As simple as it seems to us, even our nearest primate relatives fail the task miserably.

JULIANE KAMINSKI: She's not really focusing on me, and she's simply making her own choice. Most of the time, you can see that she makes a decision, long before I give my gesture. She doesn't even wait for my information.

It's such an uncooperative interaction, so it's like really I'm providing information for her to find food, which is just simply something which would never happen in a chimp group, really. I mean a chimp wouldn't go, like, "Oh, look, there's the banana." And then another chimp could go and get it.

NARRATOR: Since we're the only species that makes this gesture, it would be remarkable if any animal could understand it. But dog owners take it for granted that their dogs respond to pointing.

JULIANE KAMINSKI: Good boy!

NARRATOR: For Kaminski, it's proof of their extraordinary social intelligence.

JULIANE KAMINSKI: If you really look at that gesture, it's an informative gesture. So it's, in its essence, a very cooperative interaction, so, I'm really helping you to find something. And for dogs, following, pointing seems to be very natural, and it makes dogs extremely interesting.

NARRATOR: In fact, dogs are so tuned in to our social cues, they can even pick up on something as subtle as the direction of our gaze.

Humans have unique almond-shaped eyes with exposed white sclera visible on each side.

JULIANE KAMINSKI: One hypothesis is that we have evolved those eyes because we use it for communication. So, really, with human eyes, you can really tell easily which direction I'm looking.

NARRATOR: But these aren't skills that dogs use with each other. They are abilities dogs only use with us.

JULIANE KAMINSKI: I think it's very, very easy to imagine that they develop special skills in interacting with humans, because that's their new social partner, so they, kind of, learn to interpret human communication which is different from dog communication. So they, kind of, learn a second language. So you could probably say they are bilingual, yes.

NARRATOR: Even puppies as young as six weeks old seem to respond human gestures.

At least some of the time!

JULIANE KAMINSKI: If they learn it, they learn it very quickly, and it's obviously that they are ready to do it, so from the very beginning, they are ready to receive human communication.

NARRATOR: Dogs are primed to communicate with us, but just how smart are they? New research reveals their abilities extend way beyond what anyone thought.

Professor Kaminski has discovered a remarkable border collie, living in Austria, just outside Vienna. She's conducted a series of experiments and is amazed at the dog's intelligence.

JULIANE KAMINSKI: She can distinguish objects by name, which is really amazing. And she has, like, many, many words.

BETSY'S OWNER: Käse, das zebraâ¦

NARRATOR: With a vocabulary of over 340 words, Betsy is pushing the boundaries of what we think dogs are capable of.

B BETSY'S OWNER: carotte, sandwich.

NARRATOR: Betsy's owner, who prefers to remain anonymous, explains how this all started.

BETSY'S OWNER: I think it was when she was four or five months old, when she spontaneously started to connect human words to items. When we were discussing shall we play with the rope or with the ball, she immediately started to bring those items. So it was actually her idea, and, from this time on, we started to really train her on different words. It was maybe one toy per week, and it worked.

JULIANE KAMINSKI: I think, on average, a well-trained dog maybe knows like fifteen commands or something. There are just a very few individuals who can do what she does.

I can tell that I can try it with my own dog and it doesn't work at all. So he could maybe distinguish two objects; she is able to use it easily, more than 300 objects. That's pretty amazing.

NARRATOR: Betsy's understanding of vocabulary rivals that of a two-year-old, so Kaminski wants to test her comprehension on other skills, as well.

WOMAN 5 (Teacher of Two-Year-Olds): Can you go find me one of them, over there? Yeah?

NARRATOR: Two-year-olds are just beginning to understand how to use symbols, such as scale models, in communication. Though it looks easy, it requires abstract thinking way beyond the capability of almost all animals.

But would Betsy be able to do this, too?

BETSY'S OWNER: Ja. Ist gut.

JULIANE KAMINSKI: This was something the owners had never tried before, so when I came and I said I want to do this, they were really like, "Oh, no way, that's not going to work." I was the first one doing that with her, and she had no problem doing it, right from the beginning.

This is surprising, because, in its essence, if I hold out an object, she turns it into something communicative, and that's so interesting.

NARRATOR: Children also begin to grasp that a drawing or photograph can depict a real object.

WOMAN 5: Thank you very much. Well done.

JULIANE KAMINSKI: In essence, the picture is something very different, as the object. So it's a, it's a piece of paper butâ¦and it's two dimensionalâ¦but it's representing something, so she obviously interprets that as representing an object, a three-dimensional object, and that's so interesting that she does this. "I know exactly what you want. This is the one you want, and I'm going to go and get it for you."

BETSY'S OWNER: Ja gut. Super braves, Madchen, gut gemacht, super.

NARRATOR: Kaminski is unsure how many dogs might have similar abilities, but Betsy has shown that certain dogs may have the potential to be more intelligent than we ever thought possible.

So how did dogs acquire these unique abilities? Did these evolve over thousands of years, or is it, rather, the way dogs have been raised in a human environment?

Dogs and wolves are still the same species today. They can easily interbreed. Overall, wolves and dogs are 99.8 percent genetically identical. Given that they're biologically so similar, is it the way we raise them in our homes that makes a dog?

Researchers in Hungary set out to answer this question.

DR. KUBINYI ENIKí (Eí¶tví¶s Lorí¡nd University, Hungary): We wanted to see whether the special relationships between humans and dogs are due to nature or nurture. So, we wanted to see what happens if a wolf is raised in a human environment, in a home, whether it would act like, like a dog or not.

NARRATOR: A litter of five-day-old cubs is taken from a wolf sanctuary outside Budapest. A group of young researchers are their adoptive parents, caring for them 24 hours a day.

As a control for the experiment, they already raised puppies. Now they aim to raise the wolf cubs in the same way.

KUBINYI ENIKí: So we were especially nice with, with our cubs, because we wanted to maintain a very good relationship with them. They were really cute, so it was not very difficult to carry them everywhere we were going. And we also slept together with, with the cubs.

So the bonding, it was good. I really liked my cubs, and there was a strong, really strong relationship between us.

NARRATOR: Then something changed. Despite raising the cubs in the same way as the puppies, at eight weeks, differences start showing up.

KUBINYI ENIKí: Dog puppies were always interested in what, what I was doing. There is a very strong cooperative tendency in dogs, and this was missing in, in wolves. They had their own ideas; they were not much interested in my activities.

NARRATOR: The researchers want to find out exactly what is going on and decide to run a series of tests comparing the wolf cubs with puppies of the same age. The puppies engage. The wolves don't.

Unlike dogs, the wolf cubs do not respond to pointing. In fact, they hardly make eye contact with humans at all. The cubs behave the same as they would in the wild.

KUBINYI ENIKí: She was really possessive. If she wanted to grab an object, it was really difficult to get it back. And if we wanted to open the refrigerator and have breakfast, the pup was immediately in the middle of the refrigerator and grabbed something. It is not like with a dog that you say, "No, you shouldn't." It just didn't care.

NARRATOR: The battles worsened.

KUBINYI ENIKí: After the second month, we started to have more and more conflicts, and the wolves wanted to destroy everything.

And of course, when the cub is a small cub, it's nothing, but when they reach 40 or 50 kilograms, you know, it starts to be really dangerous. We just could not keep them in the house anymore.

NARRATOR: After four months, the cubs had to be returned to the reserve. The experiment shows that upbringing has little impact. It's impossible to turn a wolf into a dog, no matter how much it is loved and nurtured.

KUBINYI ENIKí: So according to our experiences, the dog is not a socialized wolf at all. These differences we experienced in the communicative ability and in the social behavior of dogs, this is the effect of domestication.

NARRATOR: The differences must lie in the way dogs have been bred by humans over thousands of years. Their unique abilities are now part of their nature.

But how did dogs evolve these innate attributes? Can we figure out what made them tame? A remarkable experiment in Siberia may hold the key to understanding how wolves evolved into domesticated dogs.

Half a century ago, Soviet scientists set up a breeding program to see if they could domesticate silver foxes. Foxes are closely related to wolves. The project, which has attracted the attention of scientists across the world, is opening a remarkable window on the process of domestication.

Here on a farm, outside the city of Novosibirsk, the experiment still continues today, overseen by Dr Lyudmila Trut.

The breeding program began in 1959, when the first foxes were selected from local fur farms.

DR. LYUDMILA TRUT (Institute of Cytology and Genetics, Russia) [Dubbed]: We approached the animals in the cages and recorded their reaction to us. We could see that some of the foxes showed aggressive behavior, others were frightened; but only one percent of them showed neither signs of fear or aggression.

NARRATOR: This one percent is selected to become the founding generation of a new population of foxes. At every generation, the selection process is repeated, only the tamest foxes are allowed to breed. Within just three generations, the aggressive behavior begins to disappear.

LYUDMILA TRUT [Dubbed]: The radical changes came through in the eighth generation, when foxes started to seek contact with humans and show affection to them. The amazing thing was that cubs who had just started to crawl opened their eyes and started showing affection to humans by breathing heavily, wagging their tails and howling.

This kind of response was a big surprise to us.

NARRATOR: Half a century and nearly fifty generations later, the foxes are tamer than ever. It's an accelerated model of how dogs might have been domesticated from wolves.

In order to understand the role that genetics plays in the taming process, the scientists also bred a group of foxes to be more aggressive.

LYUDMILA TRUT [Dubbed]: It just bit my hand. I didn't even open the cage. I just put my hand out and it managed to bite me through the bars. This isn't a fox, it's a dragon.

NARRATOR: This experiment allows researchers to make unique comparisons between tame and aggressive foxes.

LYUDMILA TRUT [Dubbed]: We did an experiment with cross-fostering, where we gave aggressive cubs to tame mothers and vice versa. We found out that the mother's behavior does not influence that of the cub. This cub was brought up by a tame mother.

NARRATOR: The results are clear. The difference between tame and aggressive foxes is almost entirely genetic.

LYUDMILA TRUT [Dubbed]: We even took the experiment one stage further and transplanted embryos from aggressive mothers into tame mothers, but the results were the same. It proved that you can't change the gene of aggressiveness, and it will be kept and preserved for the next generation.

NARRATOR: Geneticists have already located several regions on the fox genome responsible for tameness. They're now taking blood samples from tame and aggressive foxes in an attempt to pinpoint the specific genes.

Dr. Anna Kukekova, the scientist leading this research team, makes the 5,000 mile journey to Siberia, to study the foxes.

DR. ANNA KUKEKOVA (Cornell University): Behavior is complex. We're pretty sure there will be not a single gene, but definitely the orchestra of genes which is responsible for this behavior.

NARRATOR: One fascinating result to come out of this experiment is the fact that tamer foxes are producing less adrenaline. With lower adrenaline levels, the foxes experience less fear and are less aggressive.

ANNA KUKEKOVA: He is like a doggy, you know, like the puppy who's very happy when somebody picks him up from the floor. It's unbelievable how they trust, how they trust people. And I just really admire this animal.

LYUDMILA TRUT [Dubbed]: So, within 50 years of our intensive selection process, this fire-breathing dragon has turned into a human friend.

If foxes were brought up in a domestic environment, interacting with other animals and humans, they would make fantastic pets. They are as independent as cats, but, at the same time, as devoted as any dog could be.

NARRATOR: One surprising result of this experiment is that, as the foxes' behavior changes, so does their physical appearance.

Just a few generations into the experiment, scientists noticed a curious phenomenon. The normal pattern and silver color of the coat changed dramatically in some of the tame foxes. Their tails often became curly instead of straight. Some young foxes kept their floppy ears for much longer than usual, and their limbs and tails generally became shorter than their wild counterparts'.

In effect, the tame silver foxes were beginning to look more like dogs.

BRIAN HARE: What this shows is that when you select against aggression, you get almost all the same suite of changes that you see when you compare dogs to wolves.

NARRATOR: Evolutionary anthropologist Brian Hare is visiting the breeding program in Siberia. He believes once you select for tameness, changes in appearance will naturally follow.

BRIAN HARE: I think the surprise, when thinking about dog origins, is that there's so many ways that dogs are different from wolves. So is it that you had to select for each of these traits individually?

Well, the answer from the fox work is no. If you just select for behavior, a lot of the morphological and physiological changes that we see between wolves and dogs, they just get dragged along.

You end up with this crazy variance, you know, floppy ears, curly tails, you know? All these other things that are really cute, to talk about, so you get a lot of stuff for free when you select against aggression.

NARRATOR: For Hare, this wide variety of physical traits reveals something fundamental about domestication.

BRIAN HARE: When you're selecting against aggression, what you're doing is you're favoring juvenile traits. Juveniles and infants show much less aggression than adults and, so, basically, you've frozen development at a much earlier stage. And so, you have an animal, as an adult, that looks and behaves much more like a juvenile.

It's amazing that you get all this variance that's hidden under the surface. It starts to express itself, and then, of course, later, people can directly decide, "I really like the one with the curly tail, and I'm going to take two of them, and I'm going to put them together." And then you can end up having dogs that, sort of, shift in ways people want them to go.

NARRATOR: In the past few hundred years, we've taken dogs' infantile features and emphasized them even further through selective breeding.

We've created hundreds of breeds to fulfill different roles, but some of them have been bred purely for their looks.

MORTEN KRINGLEBACH (University of Oxford, England): I think this kind of breeding really tells us a lot about what kind of people we are, what it is that we like about dogs.

YOUNG GIRL 2 (Dog Owner): I want you to describe Laddy in one word.

YOUNG BOY 1 (Dog Owner): Cute. Cute, yeah.

YOUNG GIRL 1: Cute, adorable and funny.

MAN 2: I just look at her and I, I just smile, particularly when she's sleeping. She's very, very cute.

NARRATOR: We all know we find them cute, but what is it exactly that makes us respond to dogs so powerfully?

Psychiatrist Morton Kringlebach has a theory as to why the way dogs look has such a profound impact on us.

MORTEN KRINGLEBACH: The need to nurture, I think, is something that is so deep in us that we find it very difficult to resist.

Dogs, puppies have very infant-like features, and maybe that's one of the reasons why we think they are, you know, so cute, is that they remind us of the infants that we, are, so to speak, programmed to like.

There's something about the way that the facial features are organized that makes us want to care for them, and it's about having a large forehead, it's about having large eyes, big ears. And there's something about that that almost unconsciously we cannot help ourselves but actually like.

How are you feeling in there?

We're just going to go one more scan.

NARRATOR: Dr Kringlebach is exploring how strongly we respond to these infantile features. He uses an extremely powerful machine, called a MEG scanner, that allows him to measure, in real-time, the brain's response to pictures of baby and adult faces.

MORTEN KRINGLEBACH: What we found was that within a seventh of a second, there was activity in the frontal part of the brain, just over the eyebrows, in the orbital frontal of cortex, that was present when you were looking at the infant faces but not when you were looking at the adult faces.

This part of the brain is very much involved in emotional responses, and so, what we think we may have stumbled across here, is really, in many ways, the brain equivalent of the parental instinct. There's almost like a wired-in automatic reaction.

Just as with the infant, when you are looking at dogs, you find it very hard to control your emotions. You find it very hard not to get that need to nurture.

MAN 2: Wow, look at that. What a nice belly.

FEMALE RESEARCH PARTICIPANT 1: Mushu, mushu.

YOUNG GIRL 2: Oh, Boo, you so do, oh, yeah.

NARRATOR: But when we treat dogs as if they were children, do we sometimes allow them to replace our children?

MORTEN KRINGLEBACH: They are, essentially, moving our focus away from having children onto having pets.

PETER ROWLEY-CONWY: I think we can think of little puppies brought home as parasites. They don't do anything useful, they're not perceived as a food source, they're not perceived as a guard dog. They are simply brought home for fun.

The cuckoo is perhaps quite a good analogy because the baby cuckoo, of course, being planted in somebody else's nest, prompts mother bird to look after baby cuckoo, even though there's nothing in it for the mother bird at all.

MORTEN KRINGLEBACH: I think it's safe to say that dogs have, evolutionarily, been very successful. If you compare them to wolves, you will see that wolves are now an endangered species, while dogs, of course, are all around the world.

NARRATOR: Whether they are viewed as parasites or as beloved companions, no one can deny the evolutionary success of the domesticated dog.

In fact, there are over 400 million, worldwide. And humans have created over 400 genetically distinct breeds.

Research on dogs is heading in exciting new directions. Geneticists have already mapped the genome of one breed, the boxer. Studying this genome, scientists now realize that it offers tremendous promise in curing human disease.

Dr. Elinor Karlsson, of the Broad Institute, was part of the team that mapped the boxer genome in 2005.

Elinor Karlsson (Broad Institute of MIT and Harvard): If you look in, you know, a population of humans, you'd have quite a lot of genetic variation across them. People would be quite different from one another. But, within a breed, dogs are very similar to each other.

NARRATOR: Dr. Karlsson believes that she can use that similarity to understand the genetics of human disease.

Elinor Karlsson: I think there are hundreds of diseases that are in common between dogs and humans. There is diabetes, there is various cardiac diseases, there is epilepsy, there's a lot of different cancers: bone cancers, breast cancers, brain tumors.

NARRATOR: Today, the team is taking blood samples from boxers, which are susceptible to a fatal heart disease called cardiomyopathy.

The D.N.A. in their blood could hold vital clues to the causes of the disease.

Elinor Karlsson: Once we had the dog genome sequenced, we could design a gene chip which would allow us to compare all of our sick dogs and our healthy dogs and find the genes that are causing diseases.

NARRATOR: Using a genotyping machine, Dr. Karlsson simultaneously analyzes thousands of regions of D.N.A. from boxers, with and without this disease.

Elinor Karlsson: So, what you see when you compare the sick dogs to the healthy dogs and go across the genome from chromosome 1 to chromosome 2 and across, is that most of the points are right near zero, and there's not a lot of differences between the healthy dogs and the sick dogs, until you get to chromosome 17. And there, all of a sudden, you have a huge number of differences. And this is really exciting, because this means that this is the region of the genome that holds the gene that's causing our disease.

NARRATOR: Now, with the mutation's identity known, the team is able to locate the corresponding gene in humans. It's accelerated a process that, without dogs, could have taken decades.

Elinor Karlsson: I think that there's probably a lot of diseases that are so complicated in humans, dogs, basically, give us a huge head start on that.

We can really say that dogs are good for our health.

NARRATOR: For a pet that has been around so long, dog research is a surprising new area of science.

Experiments have shown what dog owners have always suspected: after thousands of years of living together, dogs are attuned to us like no other animal.

MAN 2: It's a very important part of life to actually know a dog, and especially a dog that adores you like this. It's got to be good for yourself.

FEMALE RESEARCH PARTICIPANT 1: It's kind of impossible to have a bad day when you are coming home to a wet nose and a waggy tail, I think. I can't imagine life without her.

WOMAN 3: It's quite strange. We weren't lacking anything before we had him, and yet, now, we would feel we were lacking if he wasn't here.

MAN 1: They just enrich your life. They are the best thing ever. They keep you young.

NARRATOR: New research has taken our understanding of how dogs evolved to a whole new level, getting us closer to what exactly it means to be tame.

DANIEL MILLS: While we can have good relationships with a wide variety of animals, historically, our relationship with dogs seems to have been the longest one with any domestic animal.

GREGER LARSON: I think one reason that there are almost seven billion people on Earth is, in large part, due to the role that dogs have played in our evolutionary existence.

DANIEL MILLS: Personally, I don't think it's any coincidence that the dog is referred to as man's best friend.