Dogs and Cats

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Dogs and cats


Wolves, the ancestors of today's domestic dog, are social creatures who cooperate with each other to hunt down prey. These social and hunting skills of course proved useful for eventual cohabitation with humans. Canis familiaris, the domestic dog, has been living with humans for a long time: longer than cats, longer than horses, longer than any other animal. While some might argue that the dog is no longer man's best friend, having been supplanted in popularity by the cat, it's a safe bet that dogs are man's oldest friends.

The domestication of the dog

But just when and where were dogs first domesticated? A series of three articles published in Science (November 2002) shed a great deal of light on the domestication of dogs. One of these studies, by Peter Savolainen and his Swedish and Chinese coworkers, suggest that dogs were first domesticated somewhere in east Asia about 15,000 years ago. Savolainen and his co-researchers compared mitochondrial DNA samples taken from over 600 domestic dogs throughout the world. It takes time for variability to develop in DNA samples. Therefore, the greater the DNA variability, the longer that type of animal has existed. Although all of the sampled dogs shared a common gene pool indicating a common ancestry, East Asian dogs exhibited the greatest variability in DNA, suggesting that dogs have lived there longer than anywhere else in the world.

By estimating how long it would take for these changes in DNA to occur, Savolainen theorized that dogs became domesticated about 15,000 years ago. Although this seems like quite a long time, other researchers had estimated that domestication had occurred as far back as 135,000 years ago. Savolainen admits that a different interpretation of his data could lead to the conclusion that domestication of dogs in east Asia occurred 40,000 years ago, a much longer time frame, but still much less than 135,000 years.

A second study focused on DNA samples taken from domestic dogs who lived in the Old and New World, including samples taken from dog bones of canids that had died before the arrival of Europeans in the Western hemisphere. Based on their results, Jennifer Leonard and her colleagues concluded that New World dogs are not the descendants of local wild species but are instead related to Old World wolves and arrived in the Western Hemisphere 10,000 to 15,000 years ago, when they traveled together with humans over the Bering Strait land bridge.

Interestingly, DNA taken from contemporary New World species, such as the Mexican hairless, show that modern New World dogs are descended from canines that traveled over from Europe, not from pre-Columbian New World dogs. Leonard did not find why the descendants of the dogs that crossed the Bering Strait apparently died out within the last 500 years and were supplanted by the descendants of more recent immigrant European dogs.

The third of the studies reveals that domestic dogs have evolved in their abilities to understand human cues. Brian Hare and his colleagues compared the ability of adult domestic dogs, domestic puppies, adult wolves, and chimpanzees to interpret signs given by humans to communicate the location of food. In one experiment, for example, a human would indicate which one of two containers had food by reaching for, looking at, or putting a wooden block on the full container. (It was ensured that the dogs were not tipped off by scent.) Nine of the 11 dogs picked up the hint, but only two of the eleven chimpanzees.

Another experiment focused on the ability of domestic puppies who were nine to 26 weeks old to read human cues. Even those puppies who had been raised in litters and had only been exposed to humans for a few minutes daily were able to pick up on human cues as to where food had been hidden.

Other research from Siberia suggests that the transformation from wild canid to domestic dog may have taken far less time than originally thought. Since 1959, researchers have selectively bred Vulpes vulpes, the silver fox, to produce tame animals. Although it has been conducted for less than 50 years, this study has already produced impressive results. The foxes not only are tamer, but 70–80% lick and smell the human experimenters just like domesticated dogs, and will even whimper for attention.

The behavior of these foxes is not the only thing that has changed. They also are starting to develop different physical characteristics. Their tails are shorter, their ears more droopy, and they have white splotches of fur. These types of physical

variations have also occurred in domestic dogs. Another interesting characteristic has been noted in these tamed foxes that may be related to change in behavior: their brains have higher levels of serotonin, a neurotransmitter which may be linked to reduced aggression.

Some of these fox pups have been taken out of the study and raised in the experimenters' homes. One describes these pets as being "good-tempered creatures, as devoted as dogs but as independent as cats, capable of forming deep-rooted pair bonds with human beings."

The spread of dogs over the world

Relatively little is known about the spread of dogs throughout the world although, as mentioned above, many researchers now theorize that dogs spread through the New World by following humans over the Bering Strait land bridge and then across North and South America. The earliest physical indication that dogs lived with humans has been found in Israel, where the 12,000-year-old remains of a woman holding a puppy in her hands has been found. Whether it's a dog or wolf pup is not known, but it does suggest that some sort of relationship existed between humans and canines.

Dogs and humans

In spite of their usefulness as work animals, dogs have not been universally valued to the same degree. Ancient Greeks and Romans sometimes sacrificed dogs, and dogs are still used as a food source in the Far East. The Bible mentions dogs about thirty times, but only two of these references are not derogatory. Islam also takes a dim view of them as being unclean. Work dogs do exist in Arabic countries but are typically viewed as animals to be used for a specific function, not as pets or companions.

Hinduism, on the other hand, perhaps because reincarnation is an integral component of its core beliefs, offers a more positive view of dogs. A delightful story in the Mahabharata, a 2000-year-old classic of Indian spirituality, relates the attempted entry of Dharmaputra into heaven. Dharmaputra, one of the main characters in this epic, wants to take his dog with him. Heaven's gatekeeper refuses to let the dog enter into heaven. Dharmaputra then refuses to go in without his dog. At this point, the dog turns into the Lord Krishna who had only been pretending to be an animal, an ending with which many dog lovers could identify.

Dog breeds

Although most of the breeds currently in existence are relatively new, dating back a few centuries at most, the initial differentiation into breeds evidently occurred thousands of years ago. Fossil remains indicate five different types of dog dating back to approximately 4500 b.c.: hunting dogs, sheep-dogs, wolfish guard dogs, mastiff-type draft and guard dogs, and greyhound-type sight dogs.

Today, the variety of dogs is staggering. A Yorkshire terrier weighs only about 4–7 lb (1.8–3.2 kg), is 9 in (23 cm) tall, and is smaller than many cats. Mastiffs, however, typically weigh up to 190 lb (86 kg) and are 30 in (76 cm) tall.

Interestingly, both breeds originated as work dogs. The Yorkshire terrier was developed by English miners in Yorkshire who wanted a dog that would attack rats but was small enough to be carried in a pocket. Mastiffs, on other hand, go back about 2,000 years and were used by militaries.

Today, of course, dogs are extremely popular throughout much of the world. The increasing number of dog breeds is a reflection of this popularity. Out of an estimated 400 breeds of dog, the American Kennel Club recognizes about 150, forming eight groups of dog breeds: sporting, hunting, working, terrier, toy, nonsporting, herding, and miscellaneous.

Some of these groups are related to the roles that dogs have played in human society. Sporting dogs, such as pointers and retrievers, have been used to help in hunting and are still used for this purpose. These dogs are energetic and need regular exercise. Hounds have also been used for hunting. Some breeds have been used for their sense of smell in following the trail of their quarry, others for their ability to run down prey, and all have a unique vocalization (baying). Beagles and Afghans are two types of hounds.

Herding dogs, as their name indicates, have been used to herd animals. Border collies and German shepherds are two

popular breeds. Working dogs tend to be large animals and have been used to help humans by performing tasks other than hunting. Some are guard dogs, others have pulled sleds. Doberman pinschers, great Danes, and Siberian huskies are working dogs.

Toys are at the other end of the size continuum. Pekinese, poodles, and Yorkshire terriers all belong to the toy group. While some of these animals have been work animals, such as ratters, others have been bred as companion animals. Terriers were bred to control rodents, somewhat like a canine version of the cat. There are about two dozen or so recognized breeds.

The nonsporting group includes recognized breeds that do not fit into any of the above groups. They range from the Bichon frise, which weighs about 10 lb (4.5 kg), to the Dalmatian, which weighs in at about 50 lb (23 kg). Their backgrounds are similarly varied. The bichon frise started out as a pet of European royalty and became a circus performer after it fell out of favor, while Dalmatians have been used for everything from guarding and shepherding to being the mascot of fire fighters. The miscellaneous group currently consists of seven breeds which do not quite as yet meet the American Kennel Club's requirements for fully recognized breeds.


The domestication of cats

Although cats have not been domesticated for as long as dogs, felines have lived with humans for thousands of years. The earliest indication that cats may have lived with people dates back approximately 10,000 years. A cat's tooth from 9000 b.c. was found in the remains of a settlement in Jericho, Israel.

The next oldest remain dates back to about 5000–6000 b.c. in Cyprus, where the remains of cats and humans have been found in the same area. Since cats are not native to this Mediterranean island, it is assumed that humans brought cats there. Not surprisingly, the remains of rodents were also found at this site, suggesting that humans were using cats to control pest populations at that time.

It is not definitively known which species of wild cat is the ancestor of Felis catus, the domestic cat. Felis silvestris libyca, the Libyan wild cat, lived in Egypt and many experts have suggested that this wild cat is the ancestor of F. catus. A few others, however, have suggested that domestic cats are descended from Felis chaus, a jungle cat, or from cats native to Persia or Nubia. However, many experts agree that F. silvestris is the ancestor of today's domestic cats, and most come down on the side of F. silvestris libyca.

The ever closer relationship between humans and cats seems to have been an accidental offshoot of a mutually beneficial relationship. There was apparently no conscious attempt at breeding the domestic cat, but wild cats were encouraged to live in and around human settlements. Humans would deliberately leave out food for them and sometimes raised kittens, resulting in cats that were less afraid of humans than their wild parents.

Over a period of time, cats became incorporated into Egyptian life and were given the onomatopoeic name (a name that sounds like the sound an animal makes) miu. Eventually, cats and humans coexisted along the Nile River, but it is hard to decipher when cats became completely domesticated, and some might argue that cats are not completely domesticated even today.

While cats initially performed a strictly functional role in Egyptian society as mousers, Egyptians gradually started to become more emotionally attached to cats, and even reverential toward them. Many statues and drawings of cats have been unearthed, suggesting their importance to ancient Egyptians. Some of these relics even feature cats adorned with jewelry.

Along with human and other animals, cat mummies have been found in Egyptian tombs. The evidence indicates that these cats were ritualistically killed, sometimes by breaking their necks, and then embalmed. By the fifth century b.c., Egyptians were so attached to their cats that the Greek scholar Herodotus wrote that they would pluck their eyebrows in mourning when a household cat died of natural causes. Eventually, Egyptians viewed cats as being sacred creatures. Cats were associated with the goddess Bastet. Bastet sometimes was depicted as wholly feline but often had the body of a woman and the head of a cat. She was associated with fertility, joy, and beauty. Many cats lived at her largest temple in the city of Bubastis and thousands of mummies of cats have been unearthed in excavations around this ancient city.

Killing cats (outside of ritualistic events which produced the afore-mentioned mummies) eventually became a capital crime in Egypt. The historian Diodorus Siculus recorded one such incident, which resulted in a lynching.

"Whoever kills a cat in Egypt is condemned to death, whether he committed this crime deliberately or not. The people gather and kill him. An unfortunate Roman, who had accidentally killed a cat, could not be saved, either by King Ptolemy of Egypt or by the fear which Rome inspired."

Although Egypt tried to prevent the export of cats to other countries, their usefulness as mousers led to their spread elsewhere around the Mediterranean and, eventually, throughout the world. The two great epics of Hinduism, the Ramayana and the Mahabharata, which were written about 300 b.c., both mention cats, indicating that cats came to India well over 2,000 years ago.

It is not clear when cats first arrived in Europe, although they spread throughout the continent during the time of the Roman Empire, reaching into northern Europe by about a.d. 100.

It took a while for domestic cats to become established in North America, although at least one cat traveled on the Mayflower with the Pilgrims in 1620 and Jesuits brought some cats with them to Quebec back in the sixteenth century. However, cats did not become popular in the Americas until the eighteenth century, when they were imported into Pennsylvania for the very same reason they had become popular in Egypt thousands of years earlier—to control rodents.

While humans have primarily developed a relationship with domestic cats, their ability to hunt rodents and other pests resulted in the use of wild cats as work animals. Cheetahs, for example, have been used as hunting companions in parts of Africa and Asia, in a role similar to what falcons performed in European countries. Sometimes, however, wild cats were used in particularly gruesome situations. The use of lions and other wild cats as a public means of execution in ancient Rome is well-known.

The evolution of the domestic cat

Cats have gradually changed as they became domesticated. Obviously, they are tamer. They are also more tolerant, not just of people, but of other cats. That is why a household can have more than one cat, although anyone who shares a home with multiple cats can vouch that even domestic cats can still be quite territorial. Still, while it may take some coaxing, domestic cats can learn to live together, which is not the case for their wild cousins.

Not dependent on hunting to stay alive, domestic cats have also developed smaller bodies, teeth, and jaws than their wild cousins. Their senses of smell, hearing, and sight are not as well developed. And as camouflage in the natural environment became unimportant for an animal living with humans, the color of cats' coats changed, typically into either a solid coat of one color or a combination of solid colors and/or stripes. One breed of domestic cat, the Egyptian mau, is spotted. Also, while many cat lovers may disagree, there is evidence that domestic cats have a smaller brain capacity than their wild cousins.

The typical adult domestic cat is rather small, weighing 8–25 lb (3.6–11 kg). As domesticated cats spread over the globe, they eventually developed into different breeds. Cats, however, lack the great variety of breeds found in dogs and have never been bred to fill distinct working roles (e.g., hunting, guarding, herding) as is true for dogs. The number of cat breeds is increasing and as of 2003, The Cat Fanciers' Association recognizes 39 breeds of domestic cat ranging from the Abyssinian to the Turkish van.

Cats and humans

While always valued for their usefulness in hunting rodents and other pests, cats have not been viewed with affection in all societies. For example, during the Middle Ages, cats became associated with witchcraft, first in Christian countries in Europe and then in America. In 1494, Pope Innocent VIII declared that witches could take the form of animals such as cats.

Islamic countries, however, have traditionally viewed cats in a positive light. Mohammed is reported to have been particularly fond of cats. One popular story relates that when a cat fell asleep while lying on Mohammed's garment, the Prophet cut off the sleeve so he would not disturb the sleeping cat when he had to stand up.

Cats and wildlife

Domestic cats are hunters. They will prey upon wildlife even when they are fed and cared for by humans. If not controlled, cats can have a disastrous effect on local birds. For example, their introduction to the California Channel Islands and northwestern Baja California resulted in the elimination of three local populations of seabirds and the extinction of the Guadalupe storm-petrel (Oceanodroma macrodactyla). One researcher has estimated that cats kill approximately 39 million birds—just in the state of Wisconsin—each year.

Control is difficult. While "belling the cat" is a traditional strategy, cats can eventually figure out how to move without making the bell ring out. It is possible that an electronic alarm will be developed that would intermittently go off as a warning to potential prey.

Popular pets

According to the American Pet Products Manufacturers Association 2001–2002 National Pet Owners Survey, there are an estimated 73 million pet cats in the United States. About one out of every three households has at least one cat and, on average, have two cats. Males and females are equally popular and about 80% of all household cats are spayed or neutered.

Dogs currently are just slightly less popular than cats. Although more households (four out every ten) have a dog than a cat, most households have only one dog, resulting in about 63 million pet dogs in the United States. Dogs are slightly less likely to be spayed or neutered than cats.

The importance of spaying and neutering is emphasized by some statistics provided by the Humane Society of the United States. A female cat can have an average of three litters every year, with an average of four to six kittens per litter. Cats typically live up to 15 years and become sexually mature by the time they are a year old. Theoretically, under ideal conditions, a single female and all of her offspring could produce 420,000 cats in just seven years. Even under normal conditions, unspayed and unneutered cats can produce a huge number of kittens with nowhere to go but the local animal shelter.

Dogs are not as prolific as cats, but they still can easily over-breed. A dog can have two litters every year and there are typically six to eight puppies per litter. So one female and her offspring could, theoretically, produce 67,000 dogs in six years.

Of course, cats and dogs do not have anywhere near that many offspring, but pet overpopulation is a serious problem. It has been estimated that there are 30 million feral cats in the United States and that six to eight million cats and dogs are dropped off at shelters every year. Approximately three to four million of these animals are euthanized.

Although cats still know how to hunt, life is much more difficult for feral cats than it is for pets. It has been estimated that the typical feral cat lives for only three years and that 42% of feral kittens die before they are two months old.

Organizations have sprung up in various parts of the country to trap, sterilize, and then release feral cats in order to reduce euthanasia of cats and to protect local wildlife. One such group, the Feral Cat Coalition of San Diego, California, claims that the number of cats euthanized at local shelters decreased by almost 50% between the start of its trapneuter-release program in 1992.

Dogs, cats and people: an evolving relationship

Dogs and cats have been used as work animals ever since they first associated with humans. While cats have primarily been used exclusively to hunt rodents and pests, dogs have filled a much wider variety of roles in human society.

Sighthounds, dogs that hunt prey primarily by using their sense of sight, have existed for thousands of years. The saluki has been bred in the Middle East for at least 5,000 years and mummified salukis have been found in Egypt. Unlike other dogs, salukis are not viewed as being "unclean" in the Arabic world.

Scenthounds also are hunters but are used for their well-developed sense of smell. These dogs were bred to find prey, but some have no interest in catching quarry once they have found it. Scenthounds often have other characteristics, such as droopy, long ears which form air currents, making it easier for these dogs to pick up scents.

Terriers are a specialized form of hunting dog. Small and low to the ground, terriers have been used to hunt small mammals, such as foxes, and to keep down the pest population around homes and farms.

Herding is another traditional job for dogs. Some herding breeds have been around for millennia. The corgi, for example, is estimated to have arrived in Great Britain anywhere from 1,000 to 3,000 years ago. Many other breeds, such as the giant schnauzer and the Old English sheepdog, were herding animals hundreds of years ago.

Although it is not known how these older breeds were created, some of the more recently developed herding breeds involved a careful mix of breeds to produce just the right characteristics needed for herding animals under specific situations. Ancestors of the Australian cattle dog, for example, include collies, dingos, Dalmatians, and kelpies, resulting in a dog that could herd cattle under the often harsh conditions found in Australia.

Guard dogs have a similarly long association with humans. The Portuguese watchdog guarded sheep in Portugal back in the Middle Ages. Today, dogs such as the rottweiler are still used as guard dogs but are frequently used to protect people and property in homes and businesses, instead of livestock on ranches and farms.

Unfortunately, these dogs sometimes also had another role, especially when times were tough for their human companions. In addition to guarding livestock, they were sometimes viewed as livestock themselves. The chow chow, for example, was considered to be a particularly tasty breed.

Draft dogs worked as miniature horses, pulling carts and sleds. These dogs, not surprisingly, tend to be large. However, size is not the only asset needed to fill this role. The Siberian husky, weighing between 35 and 60 lb (16 and 27 kg), is one of the smaller draft breeds, yet it is the dog of choice for sled races due to its stamina.

Dogs have also been used as search animals for centuries. The Saint Bernard breed is particularly well known. Raised by monks in the Alps, Saint Bernards were originally bred as watchdogs and companions but eventually became legendary for saving travelers trapped in the snow during harsh European winters. The ability of dogs to be used as search animals has been refined over the last few decades. In addition to finding people by tracking their odors, dogs can be trained to detect other scents, including illegal drugs. They have been trained to recognize the smell of explosives and can be used detect minefields. Dogs have also been used in arson investigations because they can detect traces of gas and flammable liquids.

Some roles are relatively new for dogs. Formally trained seeing-eye dogs, for example, originated in Germany after World War I. Dorothy Harrison Eustis became interested in the concept and wrote a popular article about it for the Saturday Evening Post in 1927. She was approached by Morris Frank, a young man who had recently lost his sight, and she agreed to train a dog for him. Mr. Frank, in turn, helped to establish the first seeing-eye dog school in the United States.

The use of seeing-eye dogs grew in popularity and eventually included other species of animals and other tasks. According to the Americans with Disabilities Act of 1990, a service animal is "any animal individually trained to do work or perform tasks for the benefit of a person with a disability," which can range from helping a blind person walk across a busy street to picking up dropped items for a person who cannot bend over.

While it is not surprising that service dogs have a beneficial effect on their eventual owners, they also can produce beneficial effects in their trainers. For example, some prison inmates at a maximum-security prison in Washington State train service dogs. One hundred percent of the trainers are reported to have found jobs when released from jail and none of them returned to prison within a three-year period, a much better success rate than that of the average released inmate.

Animal-assisted therapy (AAT) and animal-assisted activities (AAA) are two other new ways that animals such as dogs and cats have been used to help humans. While AAT and AAA both involve animals, their uses and goals are different. AAT has specific goals and must be directed by someone who has been trained in its use. It produces measurable results, such

as improved range of motion or decreased anxiety. AAA has a more general purpose and doesn't require a measurable goal. Volunteers taking dogs and cats to nursing homes to promote social interaction among the elderly residents and taking these animals to pediatric hospitals to cheer up sick children are two examples of AAA.

Animal welfare and rights movement

Dogs and cats have given a great deal to humans—work, companionship, and affection—and people have responded to this relationship. Although animals have sometimes been viewed as nothing more than useful tools, countless humans have developed a very affectionate relationship with dogs and cats. Eventually, the affection and empathy that some people felt toward animals led to the development of organizations devoted to animal welfare and even to what is referred to as the "animal rights movement." Although most of these organizations are concerned with many species of animals, cats and dogs are typically a major focus of their efforts.

The American for the Prevention of Cruelty to Animals (ASPCA), for example, was established in 1866 by Henry Bergh. This wealthy philanthropist was appalled by the abuse some people inflicted on horses, dogs, and cats, and he and the ASPCA worked to reduce these abuses. One of the first successes of the ASPCA was the enactment of an animal anticruelty law by the state of New York. Today, it's readily accepted that animals should not be abused and anti-cruelty legislation has been passed throughout the United States.

Some animal rights groups are more controversial. People for the Ethical Treatment of Animals (PETA), for example, proposes that "animals are not ours to eat, wear, experiment on, or use for entertainment." Since its inception in 1980, PETA has influenced consumers and businesses in various ways: by working against wearing fur, hunting, and experimenting on animals; and advocating the adoption of a vegetarian diet. Some of its projects, such as the "I'd Rather Go Naked Than Wear Fur" campaign, have garnered huge amounts of publicity. Others, however, such as comparing animal suffering to the Holocaust, have garnered accusations of being insensitive and excessively reactive.

Other animal protection groups, such as the Humane Society of the United States (HSUS), founded in 1954, are more widely accepted. Indeed, the HSUS states that it is "the world's largest animal-protection organization," with seven million members and constituents and 250 employees. The HSUS envisions a world in which people satisfy the physical and emotional needs of domestic animals; protect wild animals and their environments; and change their relationships with all animals, evolving from exploitation and harm to respect and compassion. As evidenced by these groups, the relationship among cats, dogs, and humans is still evolving in many ways. Originally viewed as four-legged workers, today domesticated cats and dogs are increasingly valued for their productive roles in human society.



Fogle, Bruce. The New Encyclopedia of the Cat. London: Dorling Kindersley, 2001.

Fogle, Bruce. The New Encyclopedia of the Dog. London: Dorling Kindersley, 2000.


Hare, et al. "The Domestication of Social Cognition in Dogs." Science 298 (2002): 1634–1636.

Leonard, Jennifer, et al. "Ancient DNA Evidence for Old World Origin of New World Dogs." Science 298 (2002): 1613–1616.

Savolainen, Peter, et al. "Genetic Evidence of an East Asian Origin of Domestic Dogs." Science 298 (2002): 1610–1613.

Trut, Lyudmila. "Early Canid Domestication: The Farm-Fox Experiment." American Scientist 87 (1999): 160–165.


American Kennel Club. 260 Madison Avenue, New York, NY 10016 United States. Phone: (212) 696-8200. Web site: <>

American Society for the Prevention of Cruelty to Animals. 424 E. 92nd St., New York, NY 10128 United States. Phone: (212) 876-7700. Web site: <>

Cat Fanciers Association. P.O. Box 1055, Manasquan, NJ 08736 United States. Phone: (732) 528-9797. Fax: (732) 528-7391. E-mail: [email protected] Web site: <>

Delta Society. 585 Naches Avenue, SW, Suite 101, Renton, WA 98055 United States. Phone: (425) 226-7357. Fax: (425) 235-1076. E-mail: [email protected] Web site: <>

The Humane Society of the United States. 2100 L Street, NW, Washington, DC 20037 United States. Phone: (202) 452-1100. Web site: <>

People for the Ethical Treatment of Animals. 501 Front Street, Norfolk, VA 23510 United States. Phone: (757) 622-7382. Fax: (757) 622-0457. E-mail: [email protected] Web site: <>

The Seeing Eye. P.O. Box 375, Morristown, NJ 07963 United States. Phone: (973) 539-4425. Fax: (973) 539-0922. Web site: <>

Sue Wallace