Good Dog: Studies & Research
The classic self-recognition test gets a makeover for dogs, using smell not sight
Dogs know individuals. Your dog knows I am not you and you are not me. Your dog knows that Rudy down the block is exceptional at playing, but Spot is not.
If dogs can recognize individuals, and your dog is an individual, might your dog know himself? As an individual? Does he have a sense of “me-ness”?
Alexandra Horowitz wants to know what it’s like to be a dog. Even her Twitter bio is dog-aware: “dogs sniff me; I sniff them back.” Her popular writing and research—at Barnard College’s Dog Cognition Lab in NYC—explore the unique experiences of the dog. Her recent publication in Behavioural Processes tackles the hefty question of their self-recognition.
But first, my teeth.
It was probably a good two hours post-lunch before a bathroom mirror informed me that I had a big piece of green gunk in my teeth. I was able to make this find—accompanied by “#$@&%*! Why didn’t anyone tell me?”—because I know mirrors reflect me, Julie. Faced with a mirror, we see ourselves: our constants (yup, my eyes are still brown), and our changes (#$@&%*! that pimple wasn’t there yesterday). You and I haven’t always done this. An understanding of self-in-the-mirror appears by age two.
Since the 1970s, researchers have used the mirror as a tool to investigate self-recognition in non-human animals. The main components of the mirror-self recognition test are a mirror and an individual who has covertly been marked in some way. In the original mirror test, chimpanzees—who had secretly been marked on the face with red odorless dye—were found to use the mirror to examine the mark. Something about them had changed. They would touch the mark on their face, in the same way you might touch a newly appearing pimple on your face. Not reaching toward the mirror, but instead using the mirror to refer back to themselves. Since then, the mirror test has panned out in a number of species like chimpanzees, dolphins, Asian elephants, and European magpies.
But dogs aren’t on this list. From personal experience or entertaining YouTube videos, you know that young dogs, or dogs unfamiliar with mirrors, often treat mirrors as another dog. Over time, dogs typically come to ignore mirrors. Studies find some dogs use mirrors to gather information or solve a problem—recognizing it as a tool to help see behind themselves or locate hidden food.
If dogs don’t “pass” the mirror test, is this the end of their self-recognition story? Not so fast. Maybe the traditional mirror test isn’t the most fitting medium for questions-of-the-self in dogs.
After all, dogs are beings of smell, not sight. From quivering nostrils to sizable brain regions dedicated to olfaction, dogs are equipped to take in and process smells. Humans have harnessed this skill and taught working dogs to notice smells we designate important, like the presence of cancer or narcotics.
And then there's pee. Dogs find certain smells, like dog urine, intrinsically interesting. Dogs both leave, and investigate, urine deposits. It is pee that leads countless dogs around the world to pull humans this way and that when out on a walk (ok fine, dropped food’s also a high priority). With this in mind, Marc Bekoff, professor emeritus of Ecology and Evolutionary Biology at the University of Colorado, proposed researchers turn to urine for questions of “self” and “other” in dogs.
Bekoff’s “yellow snow” study, published in 2001, explored the topic of “me” / “my” and “you” / “your.” His field experiment was as hands-on as it sounds. Over the course of five winters, when out walking his dog Jethro, Bekoff moved urine-soaked snow to see how Jethro behaved when encountering his own pee versus that of other dogs. Jethro performed as expected, sniffing other dogs’ urine more than his own. Jethro, Bekoff suggested, “clearly had some sense of ‘self’: a sense of ‘mine-ness’ but not necessarily of ‘I-ness’.”
Alexandra Horowitz’s new study takes into account the main features of the mirror test as well as the “yellow snow” study. She devised a test explicitly suited for dogs—an olfactory mirror test. Think about it: In the visual mirror test, individuals attend to something visually different about their appearance. An olfactory mirror test, Horowitz explains, asks whether dogs attend to something changed about their own smell when their “smell image” has been changed by the addition of a new odor. This new odor, of course, aims to be equivalent to the mark, in mirror terms.
Over two experiments, Horowitz measured how long companion dogs sniffed different odor samples simultaneously presented to them in canisters. More sniffing, you can imagine, is akin to more interest. Given my interest in dog attention to chemical information—yes, I mean pee sniffing— you can imagine I was elated to participate in this study and present canisters to 36 wonderful dogs in Experiment 1. Horowitz found that dogs spent more time investigating their own urine that had been marked (modified with the addition of an odor), compared to their urine alone. “Me different,” you might conclude from the dog’s behavior.
Olfactory investigation coded when dog nose within 10 cm of canister. Credit: Horowitz 2017. Figure 3
Or maybe there’s another explanation. Dogs are neophilic, known for their interest in new things. Could it be that dogs spent more time sniffing their marked urine because they were interested in the new smell, independent of their own smell? Dog behavior better translated as: familiar smell over here = boring, but familiar smell mixed with new smell = interesting?
With this possibility in mind, dogs also investigated their own urine marked versus the mark substance itself. These trials eliminated novelty as a factor because both canisters contained the novel odor. In these trials, dogs did not differ in the amount of time spent sniffing each sample. Ruh roh. Where does that leave us?
This is where the scientific process shines. Could it be that the selectedmark itself affected the results? In the classic mirror studies, the mark aims to be inherently neutral, not highly unique or interesting on its own—an ink mark, a piece of tape, a sticker. Ho hum. The mark in Experiment 1 of the olfactory mirror test was a cancerous tissue sample from a dog, an unfamiliar odor (adding novelty) that untrained dogs are said, anecdotally, to notice. It’s possible the cancer cells were too interesting and novel, thus deviating from the neutral mark used in classic mirror tests. In fact, a number of dogs encountering canisters with the mark had pronounced “disgust” responses, highlighting that the selected mark might not have been so neutral.
Horowitz tried a different mark. Experiment 2 tested 12 dogs with a more neutral mark—anise essential oil from the sport of Nose work. In these trials, dogs replicated the main findings, investigating their own urine that had been marked more than their urine alone. But this time, dogs were also more interested in their marked urine than the mark alone, making it less likely that the mark’s novelty explained the results. Horowitz reflects, “This suggests that the longer investigation time is not tied to an interest in the mark, per se, but rather an interest in the mark when it appears in combination with or on the dog's own odour.”
With a new olfactory approach in place, studies will surely continue to refine and tease out the meaning behind dog interest in familiar—yet modified—scents. Inquiries like the olfactory mirror test put the microphone in the paws of the dog. If they could comment, I'd imagine they'd say, “Thank you for considering our pee! After all, pee means so much to us!”
This story was originally published by Scientific American. Reprinted with permission.
Good Dog: Studies & Research
Dogs’ Color Vision
When Maureen and Jay Neitz adopted an adorable, fluffy black puppy in the late 1980s, they had no idea how important she would be in making new discoveries about vision.
They were just looking for a dog who was size-appropriate for the small apartment they lived in as UC Santa Barbara PhD candidates. Eventually, the teacup Poodle they named “Retina” helped the couple prove that dogs see much more than just black and white, and that dogs’ color vision is similar to that of the 8 percent of the human population who are red-green colorblind.
Ten million Americans, most of them male, are affected with red-green colorblindness, a genetic trait carried on the X chromosome. People with this condition can’t clearly see the difference between red and green. They often mistake green for white and red for brown or dark gray.
Colorblindness might not seem like a serious disability, but it causes unexpected, and sometimes tragic, problems for humans. For example, airline pilots must be able to differentiate between colors, which someone with red-green colorblindness can’t reliably do. Color vision is, of course, crucial in being able to discern if a traffic light is red or green. According to Don Peters, a consultant to the biotech industry who has red/green colorblindness, “Sodium vapor lights look a lot like red stoplights to me. It’s confusing to drive in an area with these lights, especially at night.” As a child, he had difficulties with color-related tasks: “I can still hear my teacher asking me why I colored the tree red. I couldn’t tell the difference.”
Colorblind people miss a lot of detail that people with normal color vision take for granted: they might not see the lines on a map, or lettering printed in colors that seem bright to those with normal vision but blend in for them. This can be dangerous when reading traffic signs or medication labels. Jay Neitz pointed out that children who are colorblind often have trouble in school, and can be mistakenly diagnosed with learning disabilities or ADHD; in spite of these potential problems, schools do not test students’ color vision.
The Neitzes established that dogs see shades of yellow, blue and gray. Other colors, such as red and green, appear faded or indistinct. Jay Neitz had an “aha” moment when Retina could not find her orange ball in a green lawn. “Sometimes the ball was right in front of her, but she would sniff around in the grass, trying to find it by smell. We realized that she simply couldn’t see it, even though it was obvious to us,” he said.
As UC Santa Barbara post-docs with degrees in biochemistry, molecular biology and biopsychology, the couple had access to a lab in which they could set up a testing area. “I realized that I had the opportunity to find out, once and for all, what kind of color vision dogs really have.” Jay built an apparatus that placed dogs in front of a screen with three lit panels. He trained the dogs to touch the screen with their noses when they saw a different shade. If the dog got it right, she would receive a cheese-flavored dog treat. In order to get the dog to touch the screen, Jay used peanut butter as an incentive. Once the dog mastered that part of the test, Jay no longer used the peanut butter.
Right away, Maureen and Jay discovered that, like people, dogs were good at figuring out shortcuts to getting a treat. In addition, “About 30 percent of the time, the dog made a lucky guess,” according to Maureen. The dogs’ attention spans were short, and on more than a few days, they just didn’t feel like doing the tests. “It took six months per dog to train them,” Maureen said. In addition to Retina, the Neitzes used two Italian Greyhounds; like Poodles, they are small, intelligent, easily trained dogs. “The dogs were treated very well,” Maureen said. “We had the utmost concern for their welfare.”
In 1989, Jay Neitz co-authored “Color vision in the dog,” which was published in the journal Visual Neuroscience; the research paper confirmed that dogs do, indeed see more than black and white. That led to a years-long search for a cure for colorblindness in humans.
Along the way, Jay heard from a diverse group of people interested in animal color vision. Game wardens asked him to create a color that hunters could use to spot each other but would be invisible to deer (“blaze orange” was the result) and, more recently, hundreds of people wanted to know what he thought of “The Dress,” a photo that went viral on the Internet featuring a dress that looked white and gold to some, blue and black to others.
Even the U.S. Army expressed an interest in the couple’s research. “They wanted to know if we could give dogs infrared vision so they could see lights used in locating bombs without alerting the enemy.” Jay joked that more people than he can count have sent him the “Far Side” cartoon showing a dog praying next to a bed, with a caption that reads “And please let Mom, Dad, Rex, Ginger, Tucker, me and all the rest of the family see color.”
Today, the Neitzes are both professors of ophthalmology and color vision researchers at the University of Washington. They continue their work in the field of color vision, but they don’t use dogs anymore. “Our dog study was done purely out of curiosity,” Maureen said. Jay added, “We demonstrated that color vision is much more complex than previously known, both in animals and in humans. Somewhere in our evolutionary past, humans developed the ability to see colors, which has helped us in many ways. One important advantage to having color vision is that it helps us determine whether a piece of food is ripe, and therefore good to eat. Humans were able to spot high-calorie food without putting out too much effort.”
In 2009, the Neitzes cured colorblindness in several male squirrel monkeys using gene therapy.
According to Maureen, “Male squirrel monkeys see only blue and yellow. Therefore, they make good subjects for color vision research.” The tests that the Neitzes developed during their original study with Retina and the two Greyhounds are now “vastly improved. We use a version of the Cambridge color test intended for human color vision testing, which Jay adapted so that it can be used on animals. It uses 16 colors, all of varying saturations.”
This more accurate test helps speed up color-vision research. The monkeys were given a human gene, which allowed them to see color the way we do. According to an article in Science, “The result raises questions about how the brain understands color, and it could eventually lead to gene-therapy treatments for colorblindness and other visual disorders in humans.”
As the Neitzes get closer to giving colorblind people normal color vision, it’s inspiring to think that a teacup Poodle trying to find her ball in the grass helped make this possible.
Read more about the Neitzes’ work.
Good Dog: Studies & Research
My dog Millie, a five-pound Yorkshire Terrier, and I do almost everything together. We hike, camp, watch sporting events, grocery shop, spend all day at the bookstore and visit research labs. Everywhere we go, people are attracted to her; they want to hold her, pet her or just say hi. Why do so many people think she is so cute? Is she perceived as cute because of her looks or her behavior? As it turns out, cuteness is influenced by both physical attributes and behavior, factors that affect the perception of cuteness in a variety of animal species.
Like many infant animals, babies and puppies have several things in common: large heads, round faces, big eyes. These appealing traits have a name: Kindchenschema (baby schema). A concept introduced by Konrad Lorenz in 1942, baby schema is defined as “a set of infantile physical characteristics ... [that] motivates caretaking behavior in other individuals, with the evolutionary function of enhancing offspring survival.”
Research by Kringelbach and others suggests that this baby schema may extend beyond physical characteristics to include “positive infant sounds and smells.” It’s not hard to imagine that these findings could also be applicable to puppy whimpering and barking, and that unmistakable puppy odor.
A preference for baby schema occurs early in human development. In a study by Borgi et al. (2014), researchers used eye tracking to determine that both children and adults looked longer at pictures rated high in infantile characteristics than at those rated low. This held true for pictures of humans, cats and dogs. And as research by Dekay and McClelland has shown, humans like animals who appear more humanlike; our concern for the well-being of a species correlates strongly with the species’ similarity to ourselves.
This partially explains why pet owners have a tendency to anthropomorphize their companion animals. I often talk to Millie as though she can understand every word, and I put her in her bed and arrange everything for her comfort much as I did for my son when he was small. Some persist in treating their dogs like children even when it clearly aggravates the dog. Although it might not bother all dogs, most dogs you see wearing cute clothing and bows in their hair would probably prefer no clothing or no bows. (When groomers put a bow on Millie, she has a fit and usually manages to remove it on the car ride home.)
Behaviors such as hand shaking, rolling over, speaking on command or engaging in unusual tricks also influence our perception of a dog’s cuteness. Conversely, specific behaviors can also detract from a dog’s cuteness quota. Excessive barking, aggression or chewing everything in sight tends to diminish our perception of exactly how cute a dog is.
This biological hardwiring has an evolutionary advantage. The human response to cuteness includes protective behavior, a willingness to care for the animal and increased attention, all things that can be good for the dog. Initially, I became interested in cuteness and its influence on humans after talking with a researcher at Eastern Kentucky University who studies perception. His work focuses on the affect of canine head tilt on a dog’s “cuteness” rating. One of the things he’s found is that the same dog can receive different ratings depending on the degree of tilt.
This type of research has direct application to the dog adoption process. As mentioned, cuteness induces protective behavior, which often leads to positive human-dog interactions. It follows that these feelings may result in a decision to adopt the dog who elicits them and to overlook those who don’t.
Because the well being of dogs is heavily dependent on their relationships with humans, it’s important to understand that these often-unconscious biases affect our choices. There’s nothing wrong with loving a cute dog—as I do Millie—but dogs of all sorts need love, and their value should not be determined by how cute we think they are.
Good Dog: Studies & Research
Adults don’t always understand dogs’ behavior around kids
Supervising children and dogs when they are together is an important part of preventing dog bites as well as of protecting the well-being of both kids and canines. However, even carefully monitoring the interactions will do little to prevent trouble if the adults watching aren’t knowledgeable about dog behavior. Research has shown that adults often underestimate the risks of dog bites to children, and that children tend to engage in riskier behavior around dogs when an adult is present.
According to a study called "Adults' Ability to Interpret Canine Body Language during a Dog-Child Interaction", misinterpreting the body language of dogs during interactions with children is quite common. Three videos of young children and dogs interacting were used in this study to assess adults’ ability to understand canine body language. A panel of behavior experts considered the dogs in all three videos to be fearful and anxious, emotionally conflicted, and lacking in confidence. However, approximately two-thirds of the subjects in the study considered the dogs to be relaxed and a similar percentage thought their behavior indicated confidence.
The subjects of the study came from four different groups: 1. People with dogs and with children, 2. People with dogs but no children, 3. People with children but no dogs, and 4. People without dogs or children. Interestingly, people without dogs were more successful at interpreting the emotional states of dogs than people who are dog guardians. Dog guardians were more likely to think the dogs were relaxed than people without dogs and less likely to label their emotional state as conflicted. Parents and non-parents did not differ in their ability to interpret the emotional states of the dogs in the video, to determine the dogs’ response to the situation, or to categorize the predominant behavior of the dog (e.g. play, friendly behavior).
Previous work has yielded conflicting results about whether people with dogs are better or worse at interpreting canine body language and emotional expressions. This study suggests that experience with dogs without any theoretical knowledge of dog behavior may not enhance people’s ability to recognize signs of trouble in interactions between young children and dogs. Perhaps people with dogs are more likely to give dogs the benefit of the doubt and assume they are friendly. Similarly, people without dogs may be more cautious when observing dogs, especially around young children, and may therefore be more receptive to the possibility of danger.
The general conclusions of the study are that people have great difficulty interpreting the signs of fear and anxiety in dogs who are interacting with young children and that it is important to educate people about dog body language in order to minimize problems when dogs are interacting with young children.
Wellness: Food & Nutrition
A vet speaks out on genetically modified pet food.
Most dogs now dine on some type of genetically modified (GM) food, often in the form of corn and soy in their kibble. As these ingredients increasingly enter the food supply, we have one more reason to wonder if our shopping choices might be harming our pets.
More animal feeding studies are needed, experts say, and a recent long-term, peer-reviewed report points out why. It found that a diet of GM corn and soy led to higher rates of severe stomach inflammation in pigs, which are physiologically similar to dogs.
Robert Silver, DVM, a Boulder, Colo., holistic vet, tackled the issue earlier this year when he presented his paper, “Genetically Modified Food and Its Impact on Pet Health” at the American Holistic Veterinary Medical Association conference in Kansas City, Mo. Why did he choose this controversial topic, one that few vets even acknowledge?
Silver—a pioneer in the field of holistic veterinary medical practice—says he was inspired by a seminar he attended in Boulder on GM foods and human health. The speakers included Don Huber, a Purdue University professor, and activist Jeffrey Smith, who discussed problems, including reproductive difficulties, that have occurred in livestock fed GM crops.
“I found this seminar mind-opening,” says Silver, the lone vet in attendance. “I had always believed the PR about GM foods—that they are going to feed the world and are a good outcome of our genetic technology.”
The Food and Drug Administration, which regulates the safety of GM crops consumed by humans and animals, considers most GM plants “substantially equivalent” to traditional plants and “generally recognized as safe.” Their regulation involves a voluntary consultation process with the developer before products are brought to market.
Smith, founder of the Institute for Responsible Technology, disagrees. On its website (responsibletechnology.org), he warns that “nearly all GM crops are described as ‘pesticide plants.’ They either tolerate doses of weed killer, such as Roundup, or produce an insecticide called Bt-toxin. In both cases, the added toxin—weed killer or bug killer—is found inside the corn or soybeans we consume.”
Silver says that while “allergies, GI problems, increased risk of cancer, neurodegenerative conditions” and other ills could all be, in part, related to GM foods, “there is no objective evidence of this yet” in dogs. “However, all vets will agree that there has been an uptick in [these diseases] in the past 10 to 20 years.” The advent of GM foods in the 1990s “fits into this timing of disease increases,” he says.
His presentation referred to studies that raise doubt about the safety of biotech crops, such as one reported in 1996 in the New England Journal of Medicine, which found that genes inserted into crops can carry with them allergenic properties.
Silver says that genetic modification introduces foreign proteins that may encourage allergies, and the widely planted Bt corn, which makes its own insecticide, “could possibly cause leaky gut, the gateway to chronic disease.” Corn is a major component of most commercial pet foods. “The big problem with commercial foods is that they are manufactured at high temperatures and pressures,” which alters them and makes them “potentially more allergenic.” And commercial foods contain industrial ingredients that are “more likely to contain GM and herbicide contaminants.”
A study published last year found that GM crops engineered to withstand the toxic herbicide Roundup must now be doused with even more herbicide, since weeds have also developed resistance to it. Residues of these chemicals on crops can find their way into pet food.
A 2013 study published in the science journal Entropy reports that the heavy use of Roundup could be linked to Parkinson’s, autism, infertility and cancers. It goes on to report that residues of Roundup in food can interact with, and enhance, the damaging effects of other environmental toxins. “Negative impact on the body is insidious and manifests slowly over time as inflammation damages cellular systems throughout the body,” the study’s researchers say.
According to Silver, heightened sensitivity to dietary ingredients “is probably what we are seeing with GM foods. It is of concern that this may be driving the increase in GI problems in pets.” Although gluten probably does account for some problems with grain consumption, “I think that grain-free diets, if they are also soy free and contain protein from animals not fed GM crops, can help many dogs, due to being GM free—and not due to some allergy or gluten issue.”
To a holistic doctor, food is medicine, and Silver strongly recommends home meal preparation from individually sourced ingredients to avoid feeding GM ingredients, especially to pets who have other health problems. “I am truly a holistic practitioner in that I believe an ounce of prevention is worth a pound of cure.”
Benbrook, C.M. 2012. Impacts of genetically engineered crops on pesticide use in the U.S.—the first 16 years. Environmental Sciences Europe 24: 24.
Ordlee, J., et al. 1996. Identification of a Brazil-nut allergen in transgenic soybeans. The New England Journal of Medicine 334: 688–692.
Samsel, A., and S. Seneff. 2013. Glyphosate’s suppression of cytochrome P450 enzymes and amino acid biosynthesis by the gut microbiome: Pathways to modern diseases. Entropy 15 (4): 1416–1463.
For the past couple of decades researchers have been looking at the role that pets, especially dogs, have to play in rates of allergies in children. Many have found that, what is being termed the hygiene hypothesis, is indeed correct, meaning that a little dirt early in life helps to stave allergic diseases, including obesity.
A new study by Anita Kozyrskyj a pediatric epidemiologist of the University of Alberta in Edmonton, Canada, found further evidence of this dog-human linkage and how this lessens the development of everything from obesity to asthma.
Starting in 2013 she wondered if she could pinpoint what and how this might be happening. Her team collected fecal samples from 4-month-old infants in the Canadian Healthy Infant Longitudinal Development (CHILD) pilot study. Of the 24 respondent infants, 15 lived in house with at least a dog or cat.
What they found was that within the households with pets, the children had a higher diversity of microbes in their guts. Microbes, as we now know, can be a good thing for our gut microbiome and immune systems actually develop alongside our gut’s “germs.” Meaning that if babies grow in a more “sterile” pet-free environment, they would be more unprepared to “fight” germs as they grow up.
Kozyrskyj noted, "The abundance of these two bacteria (Firmicutes microbes) were increased twofold when there was a pet in the house," and added that the pet exposure was shown to affect the gut microbiome indirectly—from dog to mother to unborn baby—during pregnancy as well as during the first three months of the baby's life.
Also interestingly, this study suggested that the presence of pets in the house reduced the likelihood of the transmission of vaginal GBS (group B Strep) during birth, which causes pneumonia in newborns and is prevented by giving mothers antibiotics during delivery.
Kozyrskyj’s study confirms and expands on the work that many other researchers have shown that some “dirt” can be beneficial and help to ward off disease. Including one, conducted at Kuopio University Hospital in Finland in 2012, that concentrated on infants during their first year, and investigated the effect of contact with dogs on the “frequency of respiratory symptoms and infections.” Information about the length of time a dog spent indoors was also gathered, and turned out to be one of the key indicators.
The results were eye-opening. Children with dogs at home were healthier overall, had fewer infectious respiratory problems, fewer ear infections and were less likely to require antibiotics. Researchers considered these results supportive of the theory that children who live with dogs during their early years have better resistance throughout childhood. They also found that the effect was greater if the dog spent fewer than six hours inside, possibly because the longer dogs are outdoors, the more dirt they bring inside with them. The more dirt, the more “bacterial diversity.” This diversity is thought to have a protective influence by helping the child’s immune system to mature — that is, respond more effectively to infectious agents.
Then a 2013 study conducted by the University of California, San Francisco, and the University of Michigan, Ann Arbor, found that living with dogs may prevent children from developing asthma. Mice fed a solution containing dust from homes with dogs developed a resistance to respiratory syncytial virus (RSV), a childhood airway infectious agent. RSV, which is common in infants, is linked to a higher risk of childhood asthma. According to Dr. Susan Lynch of the study team, “Exposing the gastrointestinal tract to pet dust and other microbes early in life prepares it to respond appropriately to a variety of invaders. But since our modern lifestyles involve living in immaculate houses, our immune systems often overreact instead.” Early childhood is a critical period for developing protection against allergies and asthma, and exposure to pets can help.
The idea that our microorganisms may to some extent be collectively beneficial is intriguing. People and dogs have been exchanging microbes for at least 30,000 years, since the first little cave girl kissed the first proto-dog puppy smack on the muzzle. That’s a long history of sharing. It’s possible that our microorganisms are at least symbiotic, and perhaps even played a role in the dramatic domestication of the dog.
As was reported in Nature: Researchers suspect that our long association with canines means that human and dog microbiomes may have developed in tandem. The microbiome of a baby growing up without a dog (and of a puppy growing up without a human) is, in a sense, incomplete. “All of the people alive today probably had ancestors who lived in tribes that hunted with dogs,” says Jack Gilbert, director of the Microbiome Center at the University of Chicago in Illinois.”
Since 2013, Canadian researcher, Kozyrskyj has expanded her pilot study from 24 to 746 infants, around half of whom were living in households with pets. Her team then compared the babies' microbial communities.
The results were basically the same, microbial life flourished in the infants living with pets. And not only that but the “team was now able to show that babies from families with pets (70% of which were dogs) had higher levels of two types of Firmicutes microbes — Ruminococcus and Oscillospira, which have been associated with a lower risk of allergic disease and leanness, respectively.
“Pet exposure can reduce allergic disease and obesity” later in life, added Hein Min Tun, a veterinarian and microbial epidemiologist and a member of Kozyrskyj’s research team.
And while it might be too soon to predict how this finding will play out in the future, they don’t rule out the concept of a “dog in a pill” as a preventive tool for allergies and obesity. Or, as we much rather see, “dog as the pill.”
Good Dog: Studies & Research
A study of the Delboeuf illusion
Visual illusions reveal the inner working of the eyes and of the brain, and when used in comparative studies, they can teach us a lot about the differences and similarities in vision and neurological processing between species. A common research approach involves using illusions that affect perception of size and investigating whether the illusions affect choice. Allowing research subjects to choose between various options can elucidate the illusions’ effects on members of various species.
One such illusion is the Delboeuf illusion, which causes identically sized objects to appear different in size depending on what surrounds them. In the image below with dark circles of identical size, humans (and other primates) tend to overestimate the size of the circle on the left, which is surrounded by a ring that is smaller than the ring around the circle on the right.
In the study, one set of trials tested whether dogs could correctly choose larger portions of food over smaller ones. Dogs were given a choice between two piles of biscuits on plates—one pile of biscuits weighed 18 grams and the other weighed 32 grams. Once dogs chose to go for one plate, the other one was picked up and no longer available. Sometimes both portions of food were on small plates, and sometimes both were on big plates. Each dog was offered this choice multiple times. Pooling the date into one big analysis, dogs consistently chose the bigger pile of biscuits.
In another series of trials, dogs were offered a choice between equal portions of food that were presented on different size plates. The dogs had to choose between 32 grams of food on a large plate and 32 grams of food on a small plate. If dogs are susceptible to the Delboeuf illusion, the expectation is that they would choose the smaller plate even though the quantity of food was identical on both plates. Instead, dogs’ choices were no different than if they picked a plate at random with no reference to its size. They were not significantly more likely to choose the large plate or the small plate, providing evidence that the Delboeuf illusion does not affect dogs the way that it affects humans. Dogs are not fooled by the size of the plate.
Good Dog: Studies & Research
Studies on dogs following gestures.
AT TWO WEDDINGS, darling ring bearers paraded down the aisle proudly holding the prized objects. They couldn’t have been more than six. When they suddenly stopped—as six-year-olds tend to do—to look at something on the ground, guests leaned into the aisle and pointed toward the beaming faces ahead. Smiles filled the crowd as they continued on their way.
At one wedding, the ring bearer was a little boy, and at the other, a dog.
If we’ve spent any time with companion dogs, we aren’t surprised when a dog stops to check out the ground. It also shouldn’t surprise us that a dog might go where we point. Pointing is about social communication, and it often feels like dogs are right there with us, sometimes even more than members of our own species.
In the last 20 years, dogs’ attention to our communicative gestures—particularly this thing we do with our arm and finger—has attracted enormous attention from researchers around the globe. In fact, the pointing gesture is so fundamental that seemingly no article on the canine mind is complete without a sentence such as “dogs read our gestures, like pointing, more flexibly than any other animal” (New York Times), or—more boldly in Time—“While chimps and even wolves lack an innate ability to understand what pointing means, dogs come by the knowledge naturally.”
These statements tend to produce any number of reactions in dog owners, from “Obviously,” sometimes accompanied with a side of, “Why do they bother to do this research anyway?” to the flip side: “My dog doesn’t do that … what are they talking about?” Or even the more nihilistic view: “Sure they do, but who cares?”
Here’s why we care: this one little gesture, in all its complexity, could be a core feature of the intimate bond we share with dogs.
Since the late 1990s, researchers have tried to uncover why and how dogs pick up on our cues. Initially, key questions focused on whether their ability to follow the pointing gesture arose from our long-standing co-evolutionary history or, alternatively, if they learned the behavior over the course of their individual lives.
Pointing Is About Us
Pointing is something we humans do as part of our social communication, and it is useful only because we all agree on how it should be interpreted. Imagine if your point were perceived as, “Hey! Check out my fingertip. No dirt under my nail. Wonderful, huh?” Not exactly useful for communication. Fortunately, we understand that pointing creates a shared experience beyond our fingertips; pointing draws someone’s attention past our outstretched index finger to something out there in the world.
This cooperative gesture serves us well. Yelling, “Look out!” is only somewhat informative, but yelling, “Look out!” and pointing can help a fellow human locate and respond to a Frisbee sailing in at head level or Godzilla rampaging down Fifth Avenue. Communication achieved.
Despite our mothers’ reminders that pointing is rude, it has a function: it reflects our ability to hold shared attention with others, which could also indicate that someone else is aware of the same thing that we are. Pretty meta. Joint attention can thus be associated with an ability to infer others’ mental states, which is considered an important social capability in humans.
At about six months, children start following the gaze and gestures of others. We start pointing around our first birthday and become increasingly point-savvy as we age. When toddlers see something of interest and point at it, they become excited when we also look. They will also point when seeking something or to provide information (I want that. You dropped something). Regardless of how it’s used or understood at any given age or moment, pointing intrinsically aids our communication with one another.
Do Dogs Get the Point?
It shouldn’t come as a surprise that much of the academic interest in the canine mind that blossomed in the late 1990s was actually largely about us, investigating to what extent dogs responded to our communicative gestures— notably, our pointing. In research labs around the world, it has been a pointing party ever since.
Watch any program covering research into the canine mind and you’re bound to hear mention of studies involving a dog, two cups and a pointing human. The experiment, commonly referred to as the object-choice task, follows some variation of this procedure: a dog first learns he can get a treat for approaching either of two identical cups. He then watches as a person points to one of the cups. Will the dog follow the point to the cup?
Human children are quite good at this task, and numerous studies confirm that dogs are, too. From an early age, dogs are highly responsive to this gesture. Dogs do well when a person points with a foot, or bows or nods. They’ll also respond to what’s commonly referred to as a “momentary” point, in which the person points and then lowers his or her arm before the dog makes a choice. They will follow the point even when a person stands by one cup and points at the other. Although we all know smell is a major player in the canine world, it doesn’t appear to factor greatly into dog performance; when food is hidden under one cup and nobody points, they don’t do so well. Some researchers describe their performance as “remarkable” and “outstandingly flexible.”
Not all species catch our communicative drift. A bee that flies into your car will never be aided by your outstretched arm pointing toward the open window. Given dogs’ long history with us, researchers wondered whether canine sensitivity arose through the domestication process—in which case, wolves, their closest relative, might be less adept in this task—or, on the other hand, whether it’s a product of learning and dogs’ individual life experiences. Or maybe the reality is not so black-and- white. What underlies their highly flexible ability?
Wolves do not follow our gestures as flexibly as dogs. Nor do chimpanzees, our closest relatives. This isn’t to say that wolves (or chimpanzees) can’t or don’t do it. Extensively socialized wolves and enculturated chimps—those highly familiarized with human behavior— can follow our points, but dogs generally respond more readily and easily, and wolves need more exposure to perform similarly. In 2002, Brian Hare of the Duke Canine Cognition Center pulled together then-current research on dogs, wolves and chimpanzees and, in an article in Science, concluded, “Dogs’ social-communicative skills with humans were acquired during the process of domestication.”
Both Nature & Nurture Point to Success
More immediate genetic influences, like artificial selection, could also influence dogs’ skills. Márta Gácsi and colleagues at the Family Dog Project in Budapest found that while all dogs tested followed the point better than chance would predict, dogs bred for cooperative work (like gun dogs) performed better than those bred for independent work (like guard dogs). All the dogs in the study were living as pets and none had received special training, implying that genetics plays a role at some level in enhancing dogs’ ability to follow our gestures.
At the same time, individual life experiences could also contribute to a dog’s responsiveness. For example, the reactions of shelter dogs to our pointing gestures vary widely, and a small group of intensively socialized lab-raised dogs did not fare well in the task.
Lucia Lazarowski of the Comparative Cognition Laboratory at Auburn University, one of the investigators in the lab-raised dog study, saw their challenges first-hand. But when she later adopted Captain, a study participant, and informally examined his responsiveness to pointing, she found he performed much better in her home: “He actually looked in the direction I pointed and sniffed in the area I was pointing to. During the test, however, he was one of the more non-responsive dogs. Now, we like to play a game where I toss small treats around the room for him to hunt, and if he can’t find them, sometimes I’ll point to them, so he probably has picked it up from that.” Captain’s transition to canine pointfollower highlights that learning and life experiences can factor into the skill.
The person behind the point can also affect dog performance. Amy Cook, CDBC, CPDT-KA, conducted a study on the topic at the University of California, Berkeley; reporting in Animal Cognition, Cook noted that when owners and strangers were pitted against one another (in what I hope was described as a “point-off”), dogs tended to follow their owners, even when they received no reward (i.e., the point did not lead to the dog getting food). As Cook explains, “Dogs make decisions by attending preferentially to social signals from humans with whom they have become more familiar.” Many of us think it’s all about us, and our dogs might agree.
If dogs respond to the pointing gesture based on whose finger is doing the work, then again, it looks like life experiences could be controlling the switches. But not so fast: Cook suggests that this unique spin on the issue— dogs being more attentive to a familiar person—could have been shaped by evolutionary pressures to bond with a caretaker. Attachment relationships between dogs and their humans are well documented and, as Cook says, going with your person could be “a successful strategy in the long term.”
Isn’t it nice when everyone can be right? Dog responsiveness to our communicative gestures could be a product of their evolutionary history plus their ability to learn rapidly once in a human environment. In a 2009 article in Behavioural Processes, Pamela Reid, CAAB and vice president of the ASPCA’s Anti-Cruelty Behavior Team, reflects on what’s behind canine responsiveness to our social cues: “Dogs are too skilled for it to be pure trial-and- error learning. Yet it is improbable that a versatile behavior like this would be largely innate.” She suggests that what we see in dogs is an adaptive specialization of learning. “In essence, they come with a built-in head start to learn the significance of people’s gestures, in much the same way that white-crowned sparrows acquire their species-typical song and ducklings imprint on their own kind.” This fits in well with what is understood of instinctual or innate behaviors. As Jack Hailman explained in his inf luential piece in Scientific American in 1969, “How an Instinct Is Learned,” species-specific behaviors require some amount of experience and development.
When Patricia McConnell, CAAB, mulled over the pointing research on her blog, “The Other End of the Leash,” she agreed that dogs could be “predisposed to learn to follow a pointing gesture.” McConnell also highlights something you might have seen yourself: present a very young puppy with an outstretched finger and that puppy is going to approach your fingertip, not follow it to a distant location. McConnell’s point is that point-following in puppies is not automatic, although they learn it very easily.
To this, Reid adds, “Just because a skill appears early in development does not preclude learning. It does, however, demand that puppies be highly attentive to the actions of humans, a tendency that has been confirmed in studies of dog-human attachment.”
What Do You Understand, Dog?
What do dogs think of all this? What does it mean to be a dog who “understands” our pointing gesture?
A 2013 article by Ádám Miklósi and József Topál of the Family Dog Project in Trends in Cognitive Sciences concludes by highlighting that “dog social competence [appears] sometimes ‘infant-like’ or ‘human-like,’ but, importantly, the underlying mental mechanisms may turn out to be quite different.”
It’s hard enough for us to figure out if, for example, our boss is merely suggesting that we do something or telling us to do it. The same is true for dogs and the pointing gesture. Do dogs see pointing as an imperative—“You. Go there.”—or as simply providing information or a helpful suggestion—“I recommend that you go there.”—a subtle yet meaningful difference. A 2011 article published in Applied Animal Behaviour Science by Helene Pettersson and colleagues found that, like children, dogs are more likely to follow a point when it is accompanied by a cooperative tone of voice as opposed to a prohibitive tone. At the same time, dogs sometimes follow the point to an empty container, leading some to wonder whether, under certain circumstances, dogs might perceive the gesture as a command.
Like humans, dogs seem to distinguish when communication is—or is not—intended for them, although they could be relying on a more limited set of cues. Numerous studies find that initiating eye contact and using high-pitched vocalizations help dogs understand that the communication is for them. Setting is also important. In a 2011 study reported in PLoS ONE, Linda Scheider and colleagues found that if a person points to a location where a dog has never experienced reinforcement, the dog is not as likely to follow as he would be if he had previously received reinforcement there (making me wonder whether the ring-bearer dog would spontaneously follow the point to the altar).
At some level, every pointing gesture suffers from a fundamental ambiguity: we might be pointing to a particular object, or we might be pointing to a specific space that happens to be inhabited by a particular object. Usually, we can figure it out without too much cognitive difficulty. Even nine-monthold infants understand when pointing refers to an object as opposed to the place where the object is located.
How about dogs? In a study recently published in the Journal of Comparative Psychology by Tibor Tauzin and colleagues, an experimenter pointed at one of two different toys on either side of him. Before the dog could approach, the experimenter switched the location of the objects in full view of the dog. The researchers wondered whether the dog would approach the object that had initially been pointed at but that was now in a new location, or to the original location of the point. The result? Dogs did not follow the object to its new location. Instead, they approached the old location, which seems to imply that, for the dog, pointing could be more about the location than the pointed-at object.
For those of us who live or work with dogs, much of the value of pointing studies lies in what we do with the results. Despite being unflashy, the pointing gesture is actually rich in dimensions and angles that we can explore with our dogs. As Reid recommends, “Take note of your body gestures. Does your dog attend to your gestures in all cases, or only in certain contexts? Dogs are often way more sensitive than we can grasp. They’re not trying to fool you or trick you, get one over on you or cheat the system. Attending to our gestures is just what dogs do. It’s who they are.”
Cook, A., et al. 2014. My owner right or wrong: the effect of familiarity on the domestic dog’s behavior in a food-choice task. Animal Cognition 17: 461–470.
Franco, F., and G. Butterworth. 1996. Pointing and social awareness: declaring and requesting in the second year. Journal of Child Language 12(2): 307–336.
Gácsi, M., et al. 2009. Effect of selection for cooperation and attention in dogs. Behavioral and Brain Functions 5:31.
Hailman, J.P. 1969. How an Instinct Is Learned. Scientific American 221(6): 98–106.
Hare, B., et al. 2002. The domestication of social cognition in dogs. Science 298(5598): 1634–1636.
Hochman, D. 2014. You’ll Go Far, My Pet. New York Times, April 11.
Kaminski, J., et al. 2011. How dogs know when communication is intended for them. Developmental Science 15: 222–232.
——— and J. Nitzschner. 2013. Do dogs get the point? A review of dog-human communication ability. Learning and Motivation 44(4): 294–302.
Lazarowski, L., and D.C. Dorman. 2015. A comparison of pet and purpose-bred research dog (Canis familiaris) performance on human-guided object-choice tasks. Behavioural Processes 110: 60–67.
Miklósi, A., and J. Topál. 2013. What does it take to become ‘best friends’? Evolutionary changes in canine social competence. Trends in Cognitive Sciences 17(6): 287–294.
Pettersson, H., et al. 2011. Understanding of human communicative motives in domestic dogs. Applied Animal Behaviour Science 133(3-4): 235–245.
Reid, P. 2009. Adapting to the human world: Dog’s responsiveness to our social cues. Behavioural Processes 80(3): 325–333.
Scaife, M., and J.S. Bruner. 1975. The capacity for joint visual attention in the infant. Nature 253: 265–266.
Scheider, L., et al. 2011. Domestic dogs use contextual information and tone of voice when following a human pointing gesture. PLoS ONE 6(7): e21676.
———, et al. 2013. Do domestic dogs interpret pointing as a command? Animal Cognition 16: 361–372.
Tauzin, T., et al. 2015. What or where? The meaning of referential human pointing for dogs (Canis familiaris). Journal of Comparative Psychology 129(4): 334–348.
Udell, M., et al. 2008. Wolves outperform dogs in following human social cues. Animal Behaviour 76: 1767–1773.
Zimmer, C. 2009. The Secrets Inside Your Dog’s Mind. Time, September 21.
Good Dog: Studies & Research
Humans’ empathy, personality and experience play a role
People understand and react to the facial expressions of dogs in ways that are similar to their responses to people’s expressions. Dogs can distinguish positive human expressions from negative ones, showing that they perceive the emotional content of human expressions. Our mutual understanding of one another is astounding considering that we’re not all that closely related, and yet few humans are surprised by it. We feel a kinship with our canine companions that goes beyond what we share with members of any other species except our own. The biological miracle of our relationship with dogs deserves the attention of scientists, and happily, that is happening more now than ever.
One recent study investigated the role of empathy, personality and experience on people’s ratings of facial expressions. People were asked to rate the expressions (in pictures) of people and dogs showing neutral, threatening or pleasant expressions with regard to each of the basic emotions of happiness, sadness, anger/aggressiveness, surprise, disgust or fear. They also rated how negative or positive the expression was. The study, “Human Empathy, Personality and Experience Affect the Emotion Ratings of Dog and Human Facial Expressions” found that many factors affect how people perceive the expressions of others.
People’s experience plays a smaller role in interpreting facial expressions of dogs than their personality and ability to be empathetic. This suggests that people have a natural, inherent ability to understand the facial expressions of dogs. Perhaps this is because we have co-evolved with dogs over thousands of years, but it may also simply be a result of the similarity of many facial expressions between humans and dogs. We share many of the same muscles and movements as dogs, as do many other mammals, an idea that was made popular in Charles Darwin’s classic work “The Expression of the Emotions in Man and Animals” which was published in 1872. In that book, Darwin made the case that similar behavior in humans and other animals indicated similar internal emotional states, including emotions such as anger, fear, surprise, happiness, disappointment and love. He presented photographic evidence that humans and other animals reveal their emotions through similar facial expressions and behaviors.
Though the role of experience is minimal, it still has an effect on people’s interpretations of canine facial expression. People who were involved in dog-related hobbies such as agility, obedience or hunting, rated happy faces of dogs as “more happy” than people who lack such experience. Experienced people were also more likely to rate neutral expressions as happy, perhaps indicating the subtly of relaxed, content expressions in dogs, or a more positive views of dogs among people who have a lot of experience with them.
Empathy—the ability to understand the emotions and experiences of others—played an especially strong role in the way that people perceived canine expressions. People who are particularly empathetic interpreted the facial expression of dogs more intensely and more quickly than people who are less empathetic. Researchers point out that it is not known whether empathetic people are any more accurate in their assessments of canine expressions.
Personality traits such as being extroverted or being neurotic influenced people’s interpretation of facial expressions. Extroversion influenced ratings of human expressions, but not canine expressions. Neuroticism scores were correlated with lower rankings of anger/aggression in neutral expressions of both species.
The results of this study show that there are many facets to interpreting the emotional expressions of both dogs and humans, and that psychological factors in the observer have an influence. Reading dogs’ facial expressions is a talent and a skill—both natural ability and experience influence people’s reactions to them.
Culture: Science & History
Canine Origin Story
Researchers have identified the origin of cattle, horses, pigs, sheep, camels, ducks, chickens, cats and goats. But the genesis of the domestic dog, our oldest companion and the most varied, numerous and widely distributed domestic animal on the globe? We’re still trying to figure out that one.
The study of patterns of diversity is called systematics, and it is a critical subdivision of evolutionary biology. Systematics researchers (earlier called naturalists and taxonomists) sort out species’ genealogical relationships and estimate the points at which populations diverged from one another. Traditionally, they relied on observations of differences in stable physical traits like teeth, skulls and sometimes fossils. More recently, genome-wide comparisons have been used to provide detailed information about species relationships, including the question of when and where wolves became dogs.
Canis lupus familiaris exhibits the most variability in shape, size, behavior and temperament of any mammal species living on earth. About one billion dogs, a population larger than any other domestic subspecies, roam the globe. Canine fossils, some dating to as long ago as 36,000 years, are found on every continent except Antarctica.
Add to that the unusual phenomenon that extreme variation can occur in as little as one generation—a sort of evolution at hyper speed—and we begin to understand why classifying domestic dogs has challenged many of the taxonomical systems that have been used to make sense of Canidae, a family that includes wolves, jackals, foxes and dogs.
Historically, as far back as the fourth century BCE, theories of the descent of animals were the product of using philosophical approaches to relate organic life to the history of time. At first, fundamental ideas about species-change involved sorting out living beings by means of their common essential properties. Philosophers wanted to know how organic life forms were related, not where they came from.
The Greek philosopher Aristotle (384–322 BCE) endorsed the idea that natural beings were always here and always would be. He commented on the dog’s origin, not in respect to the animal’s continuous chronological past but rather, in terms of breed creation. In his view, the dog that nature created was bred to the fox to make small dogs and to bears to make big ones, perhaps making the point that breeds (although he was mistaken about cross-species hybridization) were created by humans. Still, in the Aristotelian view, dogs always existed.
As time went on, the earliest naturalists came to understand that species were related in more complicated ways, and began to devise orderly classification systems. The bigger picture of life, however, was explained within a theological context: a specific act of an omnipotent creator transformed all living things whole and complete. The revolutionary notion that every animal might not be a singular divine creation didn’t materialize until the late Middle Ages, a contradiction that had to be explored hypothetically to avoid conflict with religious doctrine.
In the late 18th century, France’s leading naturalist and the father of paleontology, Georges Cuvier (1769–1832), introduced a new way of looking at life and death. Although he was firmly in the camp of divine creationism, he theorized that animals eventually went extinct.
Earlier, 16th-century English cleric Edward Topsell (1572–1625), author of The History of Four-footed Beasts, whose worldview was defined by fire-and-brimstone religion, based his categories on morality. This was not as much of a stretch as it might seem from today’s vantage point; during Topsell’s time, people had real reason to fear wolves. For them, the predatory wolf and sagacious, noble dog provided excellent examples of two moral extremes.
Domesticated farm livestock had derived from prey species, and no other large predator had (or has) been domesticated. So it seemed illogical that the gentle, devoted dog could have evolved from the wolf. As one writer lamented, “How could such a noble animal as the dog be derived from the likes of the wolf? If evolution were true of dogs and wolves, wouldn’t every beast choose to live the noble life?” Indeed.
But as Darwin later observed, if organic beings didn’t possess an inherent tendency to vary, humans could do nothing. Unlike bears and lions, wolves, for reasons still scientifically unclear, possessed the variation necessary for the creation of the multiple hundreds of dog breeds recognized today.
The Shape of Things
Imagine how frustrating it must have been to try to make sense of how dogs were related and where they came from based on their appearance. Travel the world over and a cat will usually look like a cat, but dogs were a vexing contradiction.
The lack of understanding of the complexity of canine morphology made it difficult to unravel relationships among the ever-increasing numbers of dogs and dog-like animals being discovered on far-away, previously unexplored continents. In the Americas, many were likely Old World breeds introduced by European explorers, eventually returned to a feral state. Over time, they interbred with American Indian dogs, wolves and coyotes, defaulting to pariah-type dogs—a catchall term for semi-feral, free-ranging canines. But a misunderstanding of the distinct differences between wild, tame, domestic and feral dogs added to the confusion about how Canidae should be classified.
The father of modern taxonomy, Carl Linnaeus (1707–1778), assigned dogs both wild and domestic to groups based on their anatomy (muzzle, jaw, ear shape), tail carriage (dog tails curve when relaxed, wolf tails don’t), hair texture, limb length and behavior, criteria that are still used today.
Linnaeus’s contemporary, Georges- Louis Leclerc, Comte de Buffon (1707– 1788)—of whom Linnaeus sniffed, “Always eloquent, often incorrect”— suspected that changes in canine morphology were influenced by environmental pressures, such as climate. But, like his colleagues, Buffon did not consider change within an evolutionary context.
Dividing dogs into categories based on skull shape was Cuvier’s idea, and although his forward-thinking approach to paleontology and the history of organisms would seem to make him an advocate for evolution, he was not. Cuvier’s interest, after all, was in a species’ demise, not its origin. Nevertheless, his contributions greatly influenced Charles Darwin.
Darwin (1809–1882) believed that the dog had multiple origins: from wolves, jackals and at least one South American species. He supported the latter by referencing his observations of dogs in Patagonia who swam underwater and an unusual dog he had seen in Central America. He also advanced the idea of multi-regional domestication.
Darwin further imagined that these small populations of “inferior” native dogs were eventually supplanted by the incursion of more robust dogs introduced by Europeans, an analogy he used to demonstrate the idea of “survival of the fittest.”
Although the fundamental theory of origin is attributed to Darwin, other taxonomists previously proposed similar ideas and connections, including Jean-Baptiste Lamarck and Alfred Russel Wallace. Unlike Lamarck and Wallace, however, Darwin suggested that the evolutionary process occurred through natural selection.
Although Darwin used the breeding of dogs and other artificially selected animals as analogies to explain how natural selection worked, dogs continued to be an untidy group of animals —a puzzle that science has began to unlock by the use of genome-wide sequencing.
In the Genes
Once scientists discovered methods to explore origin at the molecular level, they began to test these historical theories. As early as the 1970s, research papers were published suggesting that dogs may have been derived from several different gray wolf populations, and that canine domestication may have happened much earlier than the fossil record’s 15,000 years ago. By the late 1990s, geneticists worldwide were working together to build a comprehensive map that would chart the evolutionary journey of domestic dogs.
The path was not smooth. Differences of opinion erupted and criticism of research methodologies undermined a delicately balanced collaboration process. Numerous studies argued for canine origin in places as diverse as East Asia, Mongolia, Siberia, Europe and Africa, with timing varying from somewhere between 15,000 and 135,000 years ago. Archeologists who’d studied ancient canine burials were relegated to the sidelines, their fossil records dismissed as “old school,” which created further dissention. Researchers struggled to find common ground, but without much success.
The debate ramped up in 2013, when UCLA evolutionary biologist Robert Wayne and his team published a comprehensive set of data suggesting that dogs evolved from a group of European wolves, now extinct, somewhere between 19,000 and 32,000 years ago.
Two years later, Peter Savolainen, a molecular biologist, and his colleagues at the Royal Institute of Technology in Stockholm published convincing results indicating that dogs originated in China, south of the Yangtze River. They estimated that this dog population split from wolves 33,000 years ago.
Both teams were sequencing DNA. Why were their findings literally all over the map?
Savolainen’s research team analyzed DNA samples from living global dog and wolf populations, then tracked DNA from least to most diverse, going back through time. The general rule is that the older a population of animals, the more diversity it has in its genome, which is a hallmark of ancient origin.
Whether these animals represented the first domesticated dogs or, rather, dogs who migrated to the region from elsewhere and split off from a more ancient dog population, is unresolved. Fossil remains of an ancestral and probably extinct population of wolves that would have been indigenous to the area would seal the deal, but researchers have yet to find them. As Savolainen notes, “We have access to some archaeological samples we are about to analyze. However, there has been quite little archaeological work, especially on animals, in the region.”
While Savolainen and his colleagues worked backward in time, Wayne’s group worked forward, tracking ancient DNA collected from prehistoric bones of wolves and wolf-like dogs, then measuring decreasing genetic diversity. As DNA becomes less diverse, it points to animals transitioning from wolves to dogs. A dead end indicates that a lineage became extinct in that particular region.
Wayne’s team sequenced ancient DNA on canid skulls and bone fragments discovered in present-day Siberia and the Czech Republic dating to between 27,000 and 33,000 years ago. The physical characteristics of the skulls—wider muzzles and foreshortened jaws—suggest that these were ancient proto-dogs, not wolves. The canids may have looked similar to today’s Arctic breeds (for example, the Siberian Husky and the Greenland Dog), but were probably much larger. Although their findings were met with skepticism, the team said their data showed that domestic dogs originated from different wolf populations at different times in different places, in a series of starts and stops. And, they added, living dogs are more closely related to ancient extinct wolves than they are to modern wolves.
In an interesting twist, Wayne’s findings reignited the theory of parallel and multi-regional proto-domestication, an idea that Darwin introduced in the 19th century and one that’s gone in and out of favor since.
Both studies have detractors. Some claim that diversity in Savolainen’s ancient dog population is a result of admixture with European dogs as people traversed the Silk Road. Those who criticize Wayne’s study maintain that he has no solid proof that the ancient bones he’s studying are definitively wolf or dog. Additionally, critics say, his study is geographically biased because he excluded samples from dogs in China based on his position that there are no ancient dogs there.
Although the two studies point in very different directions, Savolainen and Wayne may both be right. It’s possible that dogs were domesticated multiple times in different regions, and that most lineages died out when humans were faced with overwhelming challenges, like climate change. Their findings aren’t mutually exclusive.
Crunching the (Very Big) Numbers
One reason for the disparities, according to Oxford’s visionary evolutionary biologist Greger Larson, who was a part of a team that successfully mapped the origin of the pig, is that scientists studying the dog are not including enough ancient DNA in their studies.
Larson and colleague Keith Dobney, an archaeologist at the University of Aberdeen, had the idea to bring together all the evidence collected to date, find ancient canid specimens from museums, apply state-of-the-art technology and create a database bigger than anything produced before. All they had to do was convince scientists to agree to work together.
Fortunately for canine genetics, Larson was able to sell the idea that more cooperation and collaboration improves the outcome. As chief mediator and conciliator, and supported by substantial funding, he has persuaded more than 50 influential canine evolutionary scientists to join the project. Team members include archaeologists, paleobiologists, anthropologists, zooarchaeologists, paleogeologists and others.
The purpose of the study, which began in 2013 and is slated to wrap up this year, is to combine ancient DNA analysis and geometric morphometric techniques and apply them to archaeological canid remains. This, he suggests, will directly address where, when and how many times dogs were domesticated.
Geometric morphometrics, the study of form in two or three dimensions, is a powerful new way to visually quantify evolutionary relationships. It does this by correlating thousands of geometric points that identify exact places on bones—specifically, points of evolutionary significance that differ between very closely related animals such as the wolf and the dog.
Using a special camera, researchers take hundreds of 360-degree photographs. Software then transfers the pictures to a three-dimensional computerized image that emphasizes a set of tightly defined, very specific points on each bone. The process results in holographic- like images that show domestication in progress through space and time, much like a movie.
Additionally, scientists are isolating and examining ancient DNA collected from museum specimens, looking for changes in the degree of genetic diversity over long periods. This will provide a comprehensive overview of the wolf-to-dog transition from the beginning to the present.
No individual genetic fragment of DNA says This is a wolf or This is a dog. Rather, scientists tease the two apart by looking at strands of DNA and identifying and measuring similarities and differences. As differences become more extreme, the separation between wolf, proto-dog and, finally, dog is suggested.
The team hopes to isolate genetic fragments that can be linked to minor changes in the geometric morphometricimaged samples. Combining the two techniques will tell a deeper, more layered and detailed story about canine domestication.
Larson expects to analyze up to 7,000 specimens representing wolves, incipient canids and domestic dogs. “We’re taking samples from all over the world, sources in not only museums but from private collections, too. Curators are very agreeable when we ask for permission, and they’re usually very happy to have us take photos and DNA samples. They help us, and in turn, we provide more information for their collection.”
While Larson is enthusiastically optimistic about the outcome of this unprecedented project, some scientists not affiliated with the study think the findings will only add to the existing mishmash of conflicting hypotheses. But that’s how science works: come up with an answer and you invariably end up with a lot more questions.
The ongoing search to understand where, when and how many times dogs were domesticated continues to be a topic of active scholarly exploration. Besides the millions of dog lovers who are curious about the roots of our affectionate and unusual cross-species relationship, substantial scientific issues are at stake, issues that may profoundly alter the future of evolutionary theory.
Read about new developments.
Copyright © 1997-2017 The Bark, Inc. Dog Is My Co-Pilot® is a registered trademark of The Bark, Inc