Scientists give dogs their day

Research unexpectedly suggests they may hold answers to some basic biological questions

By Peter Corner and Jeremy Manier
Tribune staff reporters

friday november,22 2002

Using high-tech genetic tools and clever behavioral tests, researchers have begun to uncover the surprising story of how dogs evolved—and how humans bred their constant companions to have minds uniquely able to communicate with people.
Three studies published Friday in the journal Science join a fast-growing body of evidence about the genetic origins and behavior of dogs, including where they were first domesticated.
The reports suggest that people first bred dogs in or near China around 15,000 years ago, creating a remarkable species that outperforms wolves and even chimpanzees on some tests of social savvy.
Based on everything from simple behavioral tests to ancient dog DNA dug up from the Alaskan permafrost, the new research reflects a mounting realization among scientists that the study of dogs, once relegated
mainly to veterinary schools, may hold the key to some of the most basic questions in biology. Experts now believe that tracing the origins of dogs could reveal an unparalleled laboratory of evolution in action, as humans have made dogs the most wildly diverse species of mam-
mal on the planet in just a fraction of the time natural evolution would require. One of the new genetic studies by Swedish and Chinese researchers, based on hundreds of canine DNA samples from around the world,
indicates that just a few original groups of wolves in East Asia gave rise to all of today's canines, ranging from toy poodles to huge mastiffs.
Another new study, by anthropologist Brian Hare of Harvard University, suggests that dogs do better on some tests of cognitive ability than chimpanzees, long considered the animal with mental prowess most similar to our own.
"In the past, everybody wanted to study primates because they're our closest genetic relative," Hare said. "We think dogs offer a gold mine of information that has been neglected simply because dogs are so popular."
Raymond Coppinger, a biologist at Hampshire College in Massachusetts who has bred or trained thousands of dogs, said the Harvard paper offers some of the first evidence that dogs have minds capable of complex thoughts about other dogs or people.
"I'm not ready to make that jump quite yet," said Coppinger, co-author of the book "Dogs: A Startling New Understanding of Canine Origin, Behavior and Evolution." "But [Hare] is certainly moving me in that direction."
Centuries-old DNA
A third report by scientists at the University of California, Los Angeles, examined centuries-old DNA samples taken from dogs that lived in the Americas before European explorers arrived, including 11 specimens dug from the permafrost in Alaska and others taken from archaeological sites from Mexico to Peru.
After comparing the old DNA with that of modern wolves and dogs, the team concluded that Native Americans brought their dogs with them from Asia, rather than domesticating native wolves they found in the Americas.
"Dogs may have been the technological innovation that allowed people to survive in the Arctic and move over longer distances," said Robert Wayne, an evolutionary biologist at UCLA and co-author of the study. "They could have provided security or helped in the hunt."
Dogs fascinate genetic researchers because they have blossomed into hundreds of specialized breeds with apparently only a few genetic changes. Such subtle changes have yielded an astonishing variety of physical forms and talents, including abilities such as tracking, herding and sled racing that require the right mix of genetics and training by humans.
"The reason I study dogs is that I'm interested in the evolution of behavior," Coppinger said. "Each breed of dog is a specialist in some behavior that no other animal in the world can do as well."
For example, he said, "Sled dogs are the fastest marathon runners in the world. In the Iditarod they run five marathons a day, day after day."
The Harvard study shows that when it comes to understanding certain social cues from humans, dogs will trounce captive-raised chimpanzees and home-raised wolves. In this case, the researchers gauged the
animals' ability to read signals from people indicating the location of hidden food.
"Puppies only a few weeks old—even those that had little human contact—caught on immediately," Hare said. "They performed much better than either the chimps or wolves."
Each animal hi the study tried to find food in one of two containers after a researcher had given a subtle cue: pointing to, looking at or placing an object on top of the container with food. (Both containers smelled of food.) Only two of 11 chimps got it right the first time, compared with nine of 11 dogs that used the cues to get the food.
Wolves, which also were tested, need to read the social cues of other wolves to coordinate the hunting of the pack. Moreover, they need to expand that ability to their prey, so they know that when a moose looks to the left, for instance, it will run to the left.
"Our experiments showed that wolves aren't any good at taking that ability and generalizing it to humans," Hare said. "But my dog does. He uses social
cues from me. Without this ability, we could never train dogs to do specific tasks."
Many researchers have assumed chimps have more social cunning on such tests than virtually any other animal. But every dog owner is an expert on such matters, and the canine prowess is no shock to those who train dogs for a living.
"Of course dogs would do that," said Jennifer Boznos, owner of the Call of the Wild School for Dogs in Chicago. "These guys who work in labs are just unbelievable."
Thinking insights
But Hare said his experiments have a deeper point: The ability to understand such cues from humans means that dogs may be able to think about the thoughts of others.
"There's no question that animals, can think," Hare said. "They take in information and make decisions about what to do all the time. Tons of experiments show the same thing.
"But do they think about the thinking of others? Do they realize that other individuals know
different things and they can learn from them? Or if they know things that the others don't, can they use that information to manipulate or deceive them?"
Those abilities are thought to have helped shape the evolution of human intellect millions of years ago. Depending on Hare's further studies, it may turn out that people crafted the minds of dogs in their own image.
The study of dogs could even yield medical benefits for people and answer larger questions about evolution.
The National Human Genome Research Institute, having already sequenced the human genome, recently indicated that the dog genome will be one of its next priorities.
"Dogs are a great system for understanding.diseases and disorders linked to the genes that cause skeletal changes," said UCLA's Wayne. "The difference between a Chihuahua and a big mastiff is probably just a handful of genes—and when we find those genes it will be a profound advance in the study of cranial and skeletal development."

DOMESTICATION OF THE DOG

Veterinary Technician November 2005

Ann Wortinger, LVT, VTS (ECC)
Michigan Veterinary Specialists Southfield, Michigan

Current evidence supports the wolf as the primary wild ancestor of the present-day dog.

Today, 73.9 million dogs are owned in the United States alone.' These extremely popular pets have enjoyed a long relationship with humans. In fact, the modern-day dog is descended from the first animal species that humans domesticated. However, there is still some debate as to whether that species was the dog or the wolf. So you may ask yourself how did dogs become domesticated, and what exactly does domestication mean?
Domestication is a process of selective breeding and containment that humans use to geographically, repro-ductively, and socially isolate a large group of animals from the wild population.2'3 Eventually, through domestication, the fear response to humans is decreased in an entire species. Domestication should not be confused with taming, which decreases the fear response in an individual animal. Taming does not necessarily transfer from generation to generation, whereas domestication does.2
A species must possess certain characteristics to become domesticated. Members of the species must be easily socialized to humans, and they must have an adaptable social structure, the potential for enhanced reproduction, and skills or characteristics desirable to humans.2'3 The dog was the first species in which humans recognized these characteristics.
THE HISTORY OF DOMESTICATION
Current behavioral, morphologic, and genetic evidence supports the wolf (Canis lupus) as the primary wild ancestor of our present-day dog.2'4'5 However, there is still much debate as to exactly when this evolution occurred; estimates place it anywhere from 10,000 to 140,000 years ago. Thus it is unknown which of the two species humans actually domesticated. One plausible theory is that dogs diverged from wolves 140,000 years ago and were already a separate species by the time humans welcomed them into their camps.4
How humans accomplished their first domestication of this species is another mystery. Did they bring dogs or wolves into their camps to raise, or did the ancient animals come to them for easy access to food? We'll never know which species made the first move -human, dog, or wolf - but the result was an enduring one.
Regardless of whether the first domesticated animal was a dog or a wolf, DNA comparisons have shown that the domesticated ancestors of today's dogs probably came from one geographic origin: eastern Asia, most likely China.4-5 From there, they spread across the ancient world in the footsteps of their human companions. They followed people across the Bering Strait into the Americas 10,000 to 15,000 years ago and joined the Romans in their conquests across Europe.4'1' The earliest evidence of domesticated dogs - 14,000-year-old skeletal remains — was found in central Europe and Germany. In Israel, a burial site of a woman holding a puppy dates from 12,000 years ago.2'5
Dogs Versus Wolves
Several ancient Asian breeds, including the shar-pei and the spitz breeds (the chow chow and the various sled dogs), have the closest genetic relationship to ancestral wolves.6 Some of the breeds we perceive as ancient, such as the Pharaoh hound and Ibizan hound, are actually fairly modern recreations of this body type from other breeds.6
So what makes the domestic dog a separate species from the wolf? The two species are genetically very similar; both have 39 pairs of chromosomes, which means they can still interbreed and produce fertile offspring, as evidenced by wolf-dog hybrids. (For animals to interbreed they must have the same number of chromosomes.) However, over many generations, the dog went through certain physical and behavioral changes to make it different enough from C. lupus to be considered a separate species, Canis familiaris.2 Despite their chromosomes, the likelihood of natural interbreeding between dogs and wolves has been diminished by differences in geographic location, social behavior, and reproductive cycles, which are largely the result of the domestication of the dog.7 In making interbreeding between wolves and dogs less likely, humans not only may have helped separate the species but also are probably continuing to widen the gap between them.
THE EFFECTS OF DOMESTICATION Socialization
Modern-day dogs are easily socialized to humans. The reason for this may stem from the fact that most wolves — and humans — are highly social and form strong bonds within their groups; therefore, the attachment formed between dogs and their owners is equally strong for both parties. Young dogs have a long socialization period (5 to 12 weeks of age). During this period, social bonds are easily formed and the attachment is strong. After this period, social bonds can still be formed, but there is more of a fear response involved. In wolves, the fear response begins at 6 to 8 weeks of age. The longer socialization period in dogs seems to allow them more time to become accustomed to interacting with people.2
In dogs, the primary social attachment has shifted away from members of their own species to human caretakers. A dog reserves its effusive displays of affection for people and becomes much more reserved toward other dogs.2
Social Structure
Both wolves and dogs live in social groups. A wolf pack includes the alpha couple, littermates, and aunts, uncles, and cousins. A dog's social group can include the human family, other dogs, and other pets within the household.
Domestic dogs retain many juvenile characteristics as they become adults, one of the most important being easily elicited subordinate behavior patterns.2 Like wolves, dogs have both dominant and subordinate behaviors, but in dogs, the subordinate behaviors have been intensified.2
Wolves have social inhibitions against aggression toward members of their own pack because such conflict might interfere with Trieir ability to hunt and survive as a group. Using ritualized dominance and submission displays, wolves can resolve conflict without injuring pack members. Dogs have inherited most of these ritualized displays, but because they no longer need to cooperate with other dogs, ritualized dominance and submission displays have been unintentionally relaxed. This has allowed an increase in the intensity of the aggressive response and a decrease in the level of the stimulus needed to trigger this response.
Reproductive Potential
In wolf society, sexual maturity and social maturity (the development of strong social bonds, the onset of dominance relationships, and the active defense of territory) occur at the same time, around 18 to 24 months of age. Domestic dogs have undergone an uncoupling of these two, with sexual maturity occurring at 6 to 9 months of age but social maturity still occurring at about 2 years of age.2 The result is that dogs are sexually mature for more of their lives than wolves.
Female wolves have only one estrous cycle per year, typically in the spring, and the males only produce sperm seasonally, also in the spring. Dogs are not seasonal breeders. Females typically undergo two estrous cycles per year, and males produce
sperm throughout the year. Depending on the breed, dogs also tend to whelp larger litters than wolves.2
Combined, these factors make it possible for dogs to reproduce more often than their undomesticated counterparts. The advantage of enhanced reproductivity in domesticated species is that humans can produce the greatest number of animals in the shortest amount of time.
Desirable Characteristics
When any species undergoes domestication, specific physical and behavioral changes occur. The animals that are more desirable to humans become the ones most likely to thrive. Therefore, many of the changes that occur benefit the animals by making them more desirable to humans, not by adapting them to life in the wild.
For example, domesticated animals tend to retain more juvenile characteristics into adulthood. In dogs, these characteristics include a foreshortened muzzle, a smaller jaw with smaller and fewer teeth, a domed forehead, and a diversity in ear, tail, and coat types. The dog's haircoat has also changed in texture from a traditionally coarse adult coat to a soft and more "touchable" juvenile one.2 (Dogs with a coarse coat [e.g., the shar-pei] are selectively bred to attain that type of coat.)
Dogs also behave more like juvenile wolves. Whining is common in wolf pups, but adult wolves seldom whine. However, both dog pups and adults retain the ability to whine, especially as a communication tool with humans. Adult wolves can exhibit play behavior, but in dogs it is more easily stimulated and more exaggerated.2 Dogs also display more subordinate behavior into adulthood, with decreased dominance challenges as sexual and social maturity are achieved.2 These juvenile behaviors make dogs more accepting of human authority.
BEYOND DOMESTICATION: SELECTIVE BREEDING
Dogs were first domesticated when humans still lived in a hunter-gatherer society; most likely, humans were directly competing with wolves for the same food sources. By domesticating dogs, humans gained certain advantages. Early dogs were probably used primarily for their ability to hunt cooperatively in the tracking and retrieving of game.2 As human society evolved into an agrarian model, dogs were used as sentinels (because of their bark alarm) and as herders and guards of other domestic species.
Selective breeding was done to develop specific types of dogs for specific jobs.2 By singling out specific behaviors to be diminished or intensified, humans have bred dogs that behave in ways that are useful to human society. Dogs naturally follow the predatory sequence: they find, stalk, chase, catch, kill, dissect, and ingest their prey.2 Through selective breeding, humans have intensified single behaviors in specific breeds of dog; for example, pointers and setters specialize in finding prey; scent hounds, in stalking; sight hounds, in chasing; retrievers, in catching; and terriers, in killing. The impulses to dissect and ingest prey have been diminished because humans want "their" game intact.
Selective Breeding Versus Natural Selection
Selective breeding refers to the selection of dogs for breeding based on the presence of desired structural or behavioral characteristics. A specific breed comprises animals that, because of human choices, possess a uniform heritable appearance. However, selective breeding does not create subspecies. A subspecies is a distinctive subpopulation that is separated by geography and physical appearance from the original population. The Australian dingo and the New Guinea singing dog are thought to be wild subspecies of the domestic dog.2-"
The opposite of selective breeding is natural selection, which can be summed up in Darwin's theory of "survival of the fittest." In wolves, natural selection has produced one of the most varied species of mammals alive today, with a vast diversity in physical and behavioral types. Subspecies of adult wolves can range from 40 to 170 Ib. Great diversity in coat colors and behaviors is also obvious.2 This diversity in size, body type, and coat color transferred through the gene pool to modern dogs, giving
humans a wide range of characteristics to choose from in breeding dogs that look and behave as desired.
History of Selective Breeding
Archaeological and hieroglyphic evidence shows that distinctive dog breeds existed 3,000 to 5,000 years ago. The spitz breeds and the sight hounds are believed to be the oldest breeds of dogs, whereas the terriers are among the newest breeds.3 Most purebred dogs in existence today have some type of working dog as part of their origin.3 The ancient Romans were the first culture to breed dogs systematically and to record the functions for which each dog was used.3 The Romans had five early types of dogs: mastiffs, spitz types, greyhounds, pointers, and sheepdogs. Although they did not develop each of these breed types, they did refine them. Many more dog breeds were developed in the Middle Ages when the aristocracy was being established and hunting was of great importance as a symbol of power and status. These dogs were also bred according to their ability to work, not necessarily for their looks. Breeding records were not detailed, and breed standards did not exist.3
Competitive dog shows evolving in the late 1800s added constraints other than working ability to breeding programs.3 At that time, breed standards were established and individual breed looks evolved. This change in focus from ability to looks also started to cause many of the genetic problems seen in purebred dogs today. By concentrating the gene pool, uniformity is achieved in appearance, but any defects in an individual breed are also concentrated. Many of today's breeds come from a foundation stock of only a few animals (sometimes as few as two), necessitating inbreeding and further concentrating any genetic problems. However, because many of these dogs are bred for companionship only, function is not an issue, and humans must try to treat the problems that might otherwise be
eliminated through natural selection. Unfortunately, not all problems caused by poor breeding can be solved. Purebred dogs (e.g., pugs, Pekingese) do not need to be able to breed on their own, and they do not need to be able to whelp on their own. Human intervention and selective breeding have overcome Darwin's principles.
CONCLUSION
Many dogs today do not function in the form that they were originally bred for, and breeds continue to be developed at a wild pace. One thing that has not changed is the love and respect we have for our most ancient friend. Whether it was dogs that chose
to be domesticated or humans that chose to domesticate dogs, we will be eternally grateful for this relationship as it continues to evolve.
REFERENCES
1. American Pet Products Manufacturers Association: Industry Statistics & Trends. Accessed October 2005 at http://www.appma.org/press_ industrytrends.asp.
2. Case LP: Man and wolf, in The dog: Its Behavior, Nutrition & Health. Ames, Iowa State University Press, 1999, pp 3-15.
3. Case LP: Selective breeding: The creation of the working dog, in The Dog: Its Behavior, Nutrition & Health. Ames, Iowa State University Press, 1999, pp 17-36.
4. Milius S: Three dog eves: Canine diaspora from East Asia to Americas. Sci News Online 162(21):324, 2002. Accessed August 2005 at http://www. sciencenews.org.
5. Pennisi E: Canine evolution: A shaggy dog history. Science 298(5598): 1540-1542, 2002.
6. Tiffany-Castiglioni E: Domestication of the dog, Part II. Phi Kappa Phi Forum Winter 2005. Accessed August 2005 at http://www.fmdarticles.com.
7. Williams R: The wolf-dog hybrid: An overview of a controversial animal. Animal Welfare Information Center Newsletter 5(4):l-2, 1994-1995.
8. Tiffany-Castiglioni E: Domestication of the dog, Part I. Phi Kappa Phi Forum Summer 2004. Accessed August 2005 at http://www.fmdarticles.com.