The Dog
Dogs were domesticated from gray wolves about 20,000 years ago. They must have been very valuable to early human settlements, for they quickly became ubiquitous across world cultures.
Dogs perform many roles for people, such as hunting, herding, pulling loads, protection, assisting police and military, companionship, and, more recently, aiding handicapped individuals. This impact on human society has given them the nickname "Man's best friend" in the western world. In 2010, there were estimated to be 600 million dogs in the world.
Dogs perform many roles for people, such as hunting, herding, pulling loads, protection, assisting police and military, companionship, and, more recently, aiding handicapped individuals. This impact on human society has given them the nickname "Man's best friend" in the western world. In 2010, there were estimated to be 600 million dogs in the world.
Over the 20,000 year span the dog had been domesticated, it diverged into only a handful of landraces, groups of similar animals whose morphology and behavior have been shaped by environmental factors and functional roles. Through selective breeding by humans, the dog has developed into hundreds of varied breeds, and shows more behavioral and morphological variation than any other land mammal.
For example, height measured to the withers ranges from a few inches in the Chihuahua to a few feet in the Irish Wolfhound; color varies from white through grays (usually called "blue'") to black, and browns from light (tan) to dark ("red" or "chocolate") in a wide variation of patterns; coats can be short or long, coarse-haired to wool-like, straight, curly, or smooth.
For example, height measured to the withers ranges from a few inches in the Chihuahua to a few feet in the Irish Wolfhound; color varies from white through grays (usually called "blue'") to black, and browns from light (tan) to dark ("red" or "chocolate") in a wide variation of patterns; coats can be short or long, coarse-haired to wool-like, straight, curly, or smooth.
Humans have maintained populations of useful animals around their places of habitat since pre-historic times. They have intentionally fed dogs considered useful, while neglecting or killing others, thereby establishing a relationship between humans and certain types of dog over thousands of years.
Over these millennia, domesticated dogs have developed into distinct types, or groups, such as livestock guardian dogs, hunting dogs, and sighthounds.
To maintain these distinctions, humans have intentionally mated dogs with certain characteristics to encourage those characteristics in the offspring.
Over these millennia, domesticated dogs have developed into distinct types, or groups, such as livestock guardian dogs, hunting dogs, and sighthounds.
To maintain these distinctions, humans have intentionally mated dogs with certain characteristics to encourage those characteristics in the offspring.
Through this process, hundreds of dog breeds have been developed. Initially, the ownership of working and, later, purebred dogs, was a privilege of the wealthy.
Nowadays, many people can afford to buy a dog. Some breeders chose to breed purebred dogs, while some prefer to produce crossbred dogs, claiming that the outcross is healthier than original breeds, and avoiding linebreeding or inbreeding.
Nowadays, many people can afford to buy a dog. Some breeders chose to breed purebred dogs, while some prefer to produce crossbred dogs, claiming that the outcross is healthier than original breeds, and avoiding linebreeding or inbreeding.
Senses
Vision - Like most mammals, dogs are dichromats and have color vision equivalent to red-green color blindness in humans (deuteranopia). Dogs are less sensitive to differences in grey shades than humans and also can detect brightness at about half the accuracy of humans.
The dog's visual system has evolved to aid proficient hunting. While a dog's visual acuity is poor (that of a poodle's has been estimated to translate to a Snellen rating of 20/75, their visual discrimination for moving objects is very high; dogs have been shown to be able to discriminate between humans (e.g., identifying their owner) at a range of between 800 and 900 m, however this range decreases to 500-600 m if the object is stationary.
The dog's visual system has evolved to aid proficient hunting. While a dog's visual acuity is poor (that of a poodle's has been estimated to translate to a Snellen rating of 20/75, their visual discrimination for moving objects is very high; dogs have been shown to be able to discriminate between humans (e.g., identifying their owner) at a range of between 800 and 900 m, however this range decreases to 500-600 m if the object is stationary.
Dogs have a temporal resolution of between 60 and 70 Hz, which explains why many dogs struggle to watch television, as most such modern screens are optimized for humans at 50-60 Hz.[102] Dogs can detect a change in movement that exists in a single diopter of space within their eye. Humans, by comparison, require a change of between 10 and 20 diopters to detect movement.
As crepuscular hunters, dogs often rely on their vision in low light situations: They have very large pupils, a high density of rods in the fovea, an increased flicker rate, and a tapetum lucidum. The tapetum is a reflective surface behind the retina that reflects light to give the photoreceptors a second chance to catch the photons. There is also a relationship between body size and overall diameter of the eye. A range of 9.5 and 11.6 mm can be found between various breeds of dogs. This 20% variance can be substantial and is associated as an adaptation toward superior night vision.
As crepuscular hunters, dogs often rely on their vision in low light situations: They have very large pupils, a high density of rods in the fovea, an increased flicker rate, and a tapetum lucidum. The tapetum is a reflective surface behind the retina that reflects light to give the photoreceptors a second chance to catch the photons. There is also a relationship between body size and overall diameter of the eye. A range of 9.5 and 11.6 mm can be found between various breeds of dogs. This 20% variance can be substantial and is associated as an adaptation toward superior night vision.
New Study Shows That Dogs Use Color Vision - Smithsonia
The eyes of different breeds of dogs have different shapes, dimensions, and retina configurations. Many long-nosed breeds have a "visual streak" a wide foveal region that runs across the width of the retina and gives them a very wide field of excellent vision.
Some long-muzzled breeds, in particular, the sighthounds, have a field of vision up to 270 (compared to 180? for humans). Short-nosed breeds, on the other hand, have an "area centralis": a central patch with up to three times the density of nerve endings as the visual streak, giving them detailed sight much more like a human's. Some broad-headed breeds with short noses have a field of vision similar to that of humans.
Some long-muzzled breeds, in particular, the sighthounds, have a field of vision up to 270 (compared to 180? for humans). Short-nosed breeds, on the other hand, have an "area centralis": a central patch with up to three times the density of nerve endings as the visual streak, giving them detailed sight much more like a human's. Some broad-headed breeds with short noses have a field of vision similar to that of humans.
Most breeds have good vision, but some show a genetic predisposition for myopia (nearsightedness) such as Rottweilers, with which one out of every two has been found to be myopic. Dogs also have a greater divergence of the eye axis than humans, enabling them to rotate their pupils farther in any direction. The divergence of the eye axis of dogs ranges from 12-25 depending on the breed.
Experimentation has proven that dogs can distinguish between complex visual images such as that of a cube or a prism. Dogs also show attraction to static visual images such as the silhouette of a dog on a screen, their own reflections, or videos of dogs; however, their interest declines sharply once they are unable to make social contact with the image.
Experimentation has proven that dogs can distinguish between complex visual images such as that of a cube or a prism. Dogs also show attraction to static visual images such as the silhouette of a dog on a screen, their own reflections, or videos of dogs; however, their interest declines sharply once they are unable to make social contact with the image.
Hearing - The frequency range of dog hearing is approximately 40 Hz to 60,000 Hz, which means that dogs can detect sounds far beyond the upper limit of the human auditory spectrum.
In addition, dogs have ear mobility, which allows them to rapidly pinpoint the exact location of a sound. Eighteen or more muscles can tilt, rotate, raise, or lower a dog's ear.
A dog can identify a sound's location much faster than a human can, as well as hear sounds at four times the distance
In addition, dogs have ear mobility, which allows them to rapidly pinpoint the exact location of a sound. Eighteen or more muscles can tilt, rotate, raise, or lower a dog's ear.
A dog can identify a sound's location much faster than a human can, as well as hear sounds at four times the distance
Smell - While the human brain is dominated by a large visual cortex, the dog brain is dominated by an olfactory cortex.
The olfactory bulb in dogs is roughly forty times bigger than the olfactory bulb in humans, relative to total brain size, with 125 to 220 million smell-sensitive receptors.
The bloodhound exceeds this standard with nearly 300 million receptors. Subsequently, it has been estimated that dogs, in general, have an olfactory sense ranging from one hundred thousand to one million times more sensitive than a human's.
In some dog breeds, such as bloodhounds, the olfactory sense may be up to 100 million times greater than a human's.
The olfactory bulb in dogs is roughly forty times bigger than the olfactory bulb in humans, relative to total brain size, with 125 to 220 million smell-sensitive receptors.
The bloodhound exceeds this standard with nearly 300 million receptors. Subsequently, it has been estimated that dogs, in general, have an olfactory sense ranging from one hundred thousand to one million times more sensitive than a human's.
In some dog breeds, such as bloodhounds, the olfactory sense may be up to 100 million times greater than a human's.
The wet nose is essential for determining the direction of the air current containing the smell. Cold receptors in the skin are sensitive to the cooling of the skin by evaporation of the moisture by air currents.
Temperature
regulation - It is a common misconception that dogs do not sweat. They do
sweat, mainly through the footpads, but only a small fraction of a dog's excess
heat is lost this way.
Primarily, dogs regulate their body temperature through panting. Panting moves cooling air over the moist surfaces of the tongue and lungs, transferring heat to the atmosphere.
Dogs possess a rete mirabile, a complex system of intermingled small arteries and veins, in the carotid sinus at the base of their neck.
This acts to thermally isolate the head, which contains the brain, the most temperature-sensitive organ, from the body, which contains the muscles, where most of the heat is generated.
The result is that dogs can sustain intense physical exertion over a prolonged time in a hot environment, compared to animals which lack this apparatus; thus, a dog chasing a jackrabbit through the desert may not be able to outrun the rabbit, but it can continue the chase until the rabbit slows due to overheating.
The dog is however very vulnerable to heat in unventilated environments such as hot cars, where temperatures can quickly become fatal - even if the car is in the shade on hot summer days.
Primarily, dogs regulate their body temperature through panting. Panting moves cooling air over the moist surfaces of the tongue and lungs, transferring heat to the atmosphere.
Dogs possess a rete mirabile, a complex system of intermingled small arteries and veins, in the carotid sinus at the base of their neck.
This acts to thermally isolate the head, which contains the brain, the most temperature-sensitive organ, from the body, which contains the muscles, where most of the heat is generated.
The result is that dogs can sustain intense physical exertion over a prolonged time in a hot environment, compared to animals which lack this apparatus; thus, a dog chasing a jackrabbit through the desert may not be able to outrun the rabbit, but it can continue the chase until the rabbit slows due to overheating.
The dog is however very vulnerable to heat in unventilated environments such as hot cars, where temperatures can quickly become fatal - even if the car is in the shade on hot summer days.
Taxonomy
The domestic dog was originally classified as Canis familiaris and Canis familiarus domesticus by Carolus Linnaeus (Carl von Linné) in 1758, and was reclassified in 1993 as Canis lupus familiaris, a subspecies of the gray wolf Canis lupus, by the Smithsonian Institution and the American Society of Mammalogists.
Overwhelming evidence from behavior, vocalizations, morphology, and molecular biology led to the contemporary scientific understanding that a single species - the gray wolf, is the common ancestor for all breeds of domestic dogs however, the timeframe and mechanisms by which dogs diverged are controversial.
Canis lupus familiaris is listed as the name for the taxon that is broadly used in the scientific community and recommended by ITIS; Canis familiaris, however, is a recognised synonym.
Overwhelming evidence from behavior, vocalizations, morphology, and molecular biology led to the contemporary scientific understanding that a single species - the gray wolf, is the common ancestor for all breeds of domestic dogs however, the timeframe and mechanisms by which dogs diverged are controversial.
Canis lupus familiaris is listed as the name for the taxon that is broadly used in the scientific community and recommended by ITIS; Canis familiaris, however, is a recognised synonym.
Evaluation of intelligence
The meaning of "intelligence" in general, not only in reference to dogs, is hard to define. Some tests measure problem-solving abilities and others test the ability to learn in comparison to others of the same age.
Defining it for dogs is just as difficult. It is likely that dogs do not have the ability to premeditate an action to solve a problem. Some dogs may, however, have more drive to keep trying various things until they accidentally reach a solution and still others might have more ability to make the association between the "accident" and the result.
For example, the ability to learn quickly could be a sign of intelligence. It could be interpreted as a sign of blind subservience and a desire to please. In contrast, some dogs who do not learn very quickly may have other talents.
Defining it for dogs is just as difficult. It is likely that dogs do not have the ability to premeditate an action to solve a problem. Some dogs may, however, have more drive to keep trying various things until they accidentally reach a solution and still others might have more ability to make the association between the "accident" and the result.
For example, the ability to learn quickly could be a sign of intelligence. It could be interpreted as a sign of blind subservience and a desire to please. In contrast, some dogs who do not learn very quickly may have other talents.
An example is breeds that are not particularly interested in pleasing their owners, such as Siberian Huskies. Huskies are often fascinated with the myriad possibilities for escaping from yards and catching small animals, figuring out on their own numerous and often ingenious ways of doing both.
Assistance dogs are also required to be obedient at all times. This means they must learn a tremendous number of commands, understand how to act in a large variety of situations, and recognize threats to their human companions, some of which they might never before have encountered.
Assistance dogs are also required to be obedient at all times. This means they must learn a tremendous number of commands, understand how to act in a large variety of situations, and recognize threats to their human companions, some of which they might never before have encountered.
Many owners of livestock guardian breeds believe that breeds such as Great Pyrenees or the Kuvasz are not easily trained because their independent nature prevents them from seeing the point of such commands as "sit" or "down".
The Molosser breeds are said to be particularly sensitive to physical or vocal aggression and, as such, are generally thought to respond to positive reinforcement-based methods of training.
Hounds, (such as Beagles, Bloodhounds, and Basset Hounds), rank in the bottom tier of "The Intelligence of Dogs" list, but probably suffer from a certain approach to intelligence assessment.
These dogs are bred to have a tenacious tracking mentality, taking advantage of their acute sense of smell, and less ability in "problem solving," which is the central task of Working and Herding dogs.
The Molosser breeds are said to be particularly sensitive to physical or vocal aggression and, as such, are generally thought to respond to positive reinforcement-based methods of training.
Hounds, (such as Beagles, Bloodhounds, and Basset Hounds), rank in the bottom tier of "The Intelligence of Dogs" list, but probably suffer from a certain approach to intelligence assessment.
These dogs are bred to have a tenacious tracking mentality, taking advantage of their acute sense of smell, and less ability in "problem solving," which is the central task of Working and Herding dogs.
In addition, many dog "authorities" are unaware of the Scenthound's extraordinary ability to perceive and evaluate things other than odors. They can detect pheromones, among other things, and may have the ability to evaluate a human's or another dog's personality or disposition from as far away as 300 feet. This can be described as "conditional intelligence" where the animal is quick to learn some things, while appearing reluctant to learn others.
A question that is still being debated is whether dogs can feel emotions. Of course dogs and other animals can feel emotions.
The dog can feel; joy, sorrow, abandonment, loneliness, depression, anxiety, stress, loss, longing, pain, jealousy, affection, love, and many other emotions.
Recently, researchers have concluded that all dogs has an intelligence equivalent to a 2-year old child and can learn at least 20 different words and understand its meaning in different contexts.
The dog can feel; joy, sorrow, abandonment, loneliness, depression, anxiety, stress, loss, longing, pain, jealousy, affection, love, and many other emotions.
Recently, researchers have concluded that all dogs has an intelligence equivalent to a 2-year old child and can learn at least 20 different words and understand its meaning in different contexts.
The domestic dog has a predisposition to exhibit a social intelligence that is uncommon in the animal world.
Dogs are capable of learning in a number of ways, such as through simple reinforcement (e.g., classical or operant conditioning) and by observation.
Dogs go through a series of stages of cognitive development. As with humans, the understanding that objects not being actively perceived still remain in existence (called object permanence) is not present at birth. It develops as the young dog learns to interact intentionally with objects around it, at roughly 8 weeks of age.
Dogs are capable of learning in a number of ways, such as through simple reinforcement (e.g., classical or operant conditioning) and by observation.
Dogs go through a series of stages of cognitive development. As with humans, the understanding that objects not being actively perceived still remain in existence (called object permanence) is not present at birth. It develops as the young dog learns to interact intentionally with objects around it, at roughly 8 weeks of age.
Puppies learn behaviors quickly by following examples set by experienced dogs. This form of intelligence is not peculiar to those tasks dogs have been bred to perform, but can be generalized to myriad abstract problems.
For example, Dachshund puppies that watched an experienced dog pull a cart by tugging on an attached piece of ribbon in order to get a reward from inside the cart learned the task fifteen times faster than those left to solve the problem on their own.
For example, Dachshund puppies that watched an experienced dog pull a cart by tugging on an attached piece of ribbon in order to get a reward from inside the cart learned the task fifteen times faster than those left to solve the problem on their own.
Dogs can also learn by mimicking human behaviors. In one study, puppies were presented with a box, and shown that, when a handler pressed a lever, a ball would roll out of the box.
The handler then allowed the puppy to play with the ball, making it an intrinsic reward. The pups were then allowed to interact with the box.
Roughly three-quarters of the puppies subsequently touched the lever, and over half successfully released the ball, compared to only 6% in a control group that did not watch the human manipulate the lever.
Another study found that handing an object between experimenters who then used the object's name in a sentence successfully taught an observing dog each object's name, allowing the dog to subsequently retrieve the item.
Photo: A stray dog in Russia, Moscow - who have learned to sleep in a warm subway train.
The handler then allowed the puppy to play with the ball, making it an intrinsic reward. The pups were then allowed to interact with the box.
Roughly three-quarters of the puppies subsequently touched the lever, and over half successfully released the ball, compared to only 6% in a control group that did not watch the human manipulate the lever.
Another study found that handing an object between experimenters who then used the object's name in a sentence successfully taught an observing dog each object's name, allowing the dog to subsequently retrieve the item.
Photo: A stray dog in Russia, Moscow - who have learned to sleep in a warm subway train.
Europe 2012: A stray dog mourning his best friend who just died in a traffic accident - this tragedy happens every day across the EU and Europe.
Since many of these countries who fail in animal welfare and animal protection laws, directives and treaties are EU member states or candidate countries, and that the EU is a legal and supervisory body - ESDAW trying to influence the EU to provide better conditions and living situations for the companion animals - by establishing common laws and regulations. Common laws would also have a positive effect and help animals outside the EU membership - in the end it is the politicians' responsibility to stop this cruelty by instituting laws that prevent uncontrolled breeding. |
A dog who is forced to live alone and abandoned, eg tied alone in a garden - are subjected to a very great suffering when the dog is a distinct social pack animal.
The dog experiencing the abandoned situation as being bullied and punished by the pack (the human family). This is a big animal cruelty going on around the world, due to poor knowledge of the dog as a species and their natural needs. We should also ask ourselves why a dog is acquired and for what purpose. |
Dogs also demonstrate sophisticated social cognition by associating behavioral cues with abstract meanings. One such class of social cognition involves the understanding that others are conscious agents. Research has shown that dogs are capable of interpreting subtle social cues, and appear to recognize when a human or dog's attention is focused on them.
To test this, researchers devised a task in which a reward was hidden underneath one of two buckets. The experimenter then attempted to communicate with the dog to indicate the location of the reward by using a wide range of signals: tapping the bucket, pointing to the bucket, nodding to the bucket, or simply looking at the bucket. The results showed that domestic dogs were better than chimpanzees, wolves, and human infants at this task, and even young puppies with limited exposure to humans performed well. Psychology research has shown that human faces are asymmetrical with the gaze instinctively moving to the right side of a face upon encountering other humans to obtain information about their emotions and state. Research at the University of Lincoln (2008) shows that dogs share this instinct when meeting a human being, and only when meeting a human being (i.e., not other animals or other dogs). As such they are the only non-primate species known to do so. |
Stanley Coren, an expert on dog psychology, states that these results demonstrated the social cognition of dogs can exceed that of even our closest genetic relatives, and that this capacity is a recent genetic acquisition that distinguishes the dog from its ancestor, the wolf. Studies have also investigated whether dogs engaged in partnered play change their behavior depending on the attention-state of their partner.
Those studies showed that play signals were only sent when the dog was holding the attention of its partner. If the partner was distracted, the dog instead engaged in attention-getting behavior before sending a play signal.
Coren has also argued that dogs demonstrate a sophisticated theory of mind by engaging in deception, which he supports with a number of anecdotes, including one example wherein a dog hid a stolen treat by sitting on it until the rightful owner of the treat left the room.
Those studies showed that play signals were only sent when the dog was holding the attention of its partner. If the partner was distracted, the dog instead engaged in attention-getting behavior before sending a play signal.
Coren has also argued that dogs demonstrate a sophisticated theory of mind by engaging in deception, which he supports with a number of anecdotes, including one example wherein a dog hid a stolen treat by sitting on it until the rightful owner of the treat left the room.
Although this could have been accidental, Coren suggests that the thief understood that the treat's owner would be unable to find the treat if it were out of view. Together, the empirical data and anecdotal evidence points to dogs possessing at least a limited form of theory of mind.
A study found a third of dogs suffered from anxiety when separated from others.
A study found a third of dogs suffered from anxiety when separated from others.
A Border Collie named Chaser has learned the names for 1,022 toys after three years of training, so many that her trainers have had to mark the names of the objects lest they forget themselves. This is higher than Rico, another border collie who could remember at least 200 objects.
Testing and research - Certain intelligence tests involve the dog's ability to recognize and respond to a large vocabulary of commands. Other tests involve their desire or ability to respond to different situations.
Just as with humans, there is a wide variety of interpretations as to what makes a dog "intelligent".
Various studies have attempted to rigorously classify intelligence of dogs. A recent example is animal psychologist Juliane Kaminski's paper in Science that demonstrated that Rico, a Border Collie, could learn over 200 words.
Rico could remember the names of several items for up to four weeks after its last exposure (Kaminski eliminated the Clever Hans effect using strict protocols).
Rico was also able to interpret phrases such as "fetch the sock" in terms of its component words (rather than considering its utterance to be a single word). Rico could also give the sock to a specified person.
Just as with humans, there is a wide variety of interpretations as to what makes a dog "intelligent".
Various studies have attempted to rigorously classify intelligence of dogs. A recent example is animal psychologist Juliane Kaminski's paper in Science that demonstrated that Rico, a Border Collie, could learn over 200 words.
Rico could remember the names of several items for up to four weeks after its last exposure (Kaminski eliminated the Clever Hans effect using strict protocols).
Rico was also able to interpret phrases such as "fetch the sock" in terms of its component words (rather than considering its utterance to be a single word). Rico could also give the sock to a specified person.
In 2008, Betsy, also a Border Collie, was featured on the cover of National Geographic Magazine. Betsy's intelligence rivaled that of Rico's in that she knew over 340 words and was able to correlate an object with a photographic image of the object, despite having seen neither before.
In his 1996 book Good Natured, ethologist Frans de Waal discusses an experiment on guilt and reprimands conducted on a female Siberian husky. The dog had the habit of shredding newspapers, and when her owner returned home to find the shredded papers and scold her she would act guilty.
However, when the owner himself shredded the papers without the dog's knowledge, the dog "acted just as 'guilty' as when she herself had created the mess." De Waal concludes that the "guilt" displayed by dogs is not true guilt but rather the anticipation of the behavior of an angry superior in a given situation. A recent study in the journal PNAS concluded that dogs can feel complex emotions, like jealousy.
However, when the owner himself shredded the papers without the dog's knowledge, the dog "acted just as 'guilty' as when she herself had created the mess." De Waal concludes that the "guilt" displayed by dogs is not true guilt but rather the anticipation of the behavior of an angry superior in a given situation. A recent study in the journal PNAS concluded that dogs can feel complex emotions, like jealousy.
Psychology research has shown that human faces are asymmetrical with the gaze instinctively moving to the right side of a face upon encountering other humans to obtain information about their emotions and state.
Research at the University of Lincoln (2008) shows that dogs share this instinct when meeting a human being, and only when meeting a human being (i.e., not other animals or other dogs). As such they are the only non-primate species known to do so.
School psychologist Kathy Coon developed the first intelligence test for dogs in 1976 , with the work continuously revised through 2003.
Research at the University of Lincoln (2008) shows that dogs share this instinct when meeting a human being, and only when meeting a human being (i.e., not other animals or other dogs). As such they are the only non-primate species known to do so.
School psychologist Kathy Coon developed the first intelligence test for dogs in 1976 , with the work continuously revised through 2003.
Assessments were developed to test short term memory, agility, ability to adapt, problem solving, unique detour problems, and to see how the dog reacts to conditions which he or she finds unacceptable.
The performance of individual dogs was compared to over 100 dogs on which the test was standardized. Additional breed norms were developed in her book, The Dog Intelligence Test.
The performance of individual dogs was compared to over 100 dogs on which the test was standardized. Additional breed norms were developed in her book, The Dog Intelligence Test.
DNA - studies
DNA have provided a wide range of possible divergence dates, from 15,000 to 40,000 years ago, to as much as 100,000 to 140,000 years ago.
These results depend on a number of assumptions. Genetic studies are based on comparisons of genetic diversity between species, and depend on a calibration date.
Some estimates of divergence dates from DNA evidence use an estimated wolf-coyote divergence date of roughly 700,000 years ago as a calibration.
If this estimate is incorrect, and the actual wolf-coyote divergence is closer to one or two million years ago, or more, then the DNA evidence that supports specific dog-wolf divergence dates would be interpreted very differently.
These results depend on a number of assumptions. Genetic studies are based on comparisons of genetic diversity between species, and depend on a calibration date.
Some estimates of divergence dates from DNA evidence use an estimated wolf-coyote divergence date of roughly 700,000 years ago as a calibration.
If this estimate is incorrect, and the actual wolf-coyote divergence is closer to one or two million years ago, or more, then the DNA evidence that supports specific dog-wolf divergence dates would be interpreted very differently.
Furthermore, it is believed the genetic diversity of wolves has been in decline for the last 200 years, and that the genetic diversity of dogs has been reduced by selective breeding. This could significantly bias DNA analyses to support an earlier divergence date.
The genetic evidence for the domestication event occurring in East Asia is also subject to violations of assumptions. These conclusions are based on the location of maximal genetic divergence, and assume hybridization does not occur, and that breeds remain geographically localized. Although these assumptions hold for many species, there is good reason to believe that they do not hold for canines.
The genetic evidence for the domestication event occurring in East Asia is also subject to violations of assumptions. These conclusions are based on the location of maximal genetic divergence, and assume hybridization does not occur, and that breeds remain geographically localized. Although these assumptions hold for many species, there is good reason to believe that they do not hold for canines.
Genetic analyses indicate all dogs are likely descended from a handful of domestication events with a small number of founding females, although there is evidence domesticated dogs interbred with local populations of wild wolves on several occasions.
Data suggest dogs first diverged from wolves in East Asia, and these domesticated dogs then quickly migrated throughout the world, reaching the North American continent around 8000 BC.
The oldest groups of dogs, which show the greatest genetic variability and are the most similar to their wolf ancestors, are primarily Asian and African breeds, including the Basenji, Lhasa Apso, and Siberian Husky. Some breeds thought to be very old, such as the Pharaoh Hound, Ibizan Hound, and Norwegian Elkhound, are now known to have been created more recently.
Data suggest dogs first diverged from wolves in East Asia, and these domesticated dogs then quickly migrated throughout the world, reaching the North American continent around 8000 BC.
The oldest groups of dogs, which show the greatest genetic variability and are the most similar to their wolf ancestors, are primarily Asian and African breeds, including the Basenji, Lhasa Apso, and Siberian Husky. Some breeds thought to be very old, such as the Pharaoh Hound, Ibizan Hound, and Norwegian Elkhound, are now known to have been created more recently.
There is a great deal of controversy surrounding the evolutionary framework for the domestication of dogs. Although it is widely claimed that "man domesticated the wolf," man may not have taken such a proactive role in the process. The nature of the interaction between man and wolf that led to domestication is unknown and controversial.
At least three early species of the Homo genus began spreading out of Africa roughly 400,000 years ago, and thus lived for a considerable time in contact with canine species.
Despite this, there is no evidence of any adaptation of canine species to the presence of the close relatives of modern man. If dogs were domesticated, as believed, roughly 15,000 years ago, the event (or events) would have coincided with a large expansion in human territory and the development of agriculture.
At least three early species of the Homo genus began spreading out of Africa roughly 400,000 years ago, and thus lived for a considerable time in contact with canine species.
Despite this, there is no evidence of any adaptation of canine species to the presence of the close relatives of modern man. If dogs were domesticated, as believed, roughly 15,000 years ago, the event (or events) would have coincided with a large expansion in human territory and the development of agriculture.
This has led some biologists to suggest one of the forces that led to the domestication of dogs was a shift in human lifestyle in the form of established human settlements. Permanent settlements would have coincided with a greater amount of disposable food and would have created a barrier between wild and anthropogenic canine populations.
Etymology and related terminology
Dog is the common use term that refers to members of the subspecies Canis lupus familiaris (canis, "dog"; lupus, "wolf"; familiaris, "of a household" or "domestic").
The term can also be used to refer to a wider range of related species, such as the members of the genus Canis, or "true dogs", including the wolf, coyote, and jackals; or it can refer to the members of the tribe Canini, which would also include the African wild dog; or it can be used to refer to any member of the family Canidae, which would also include the foxes, bush dog, raccoon dog, and others. Some members of the family have "dog" in their common names, such as the raccoon dog and the African wild dog. A few animals have "dog" in their common names but are not canids, such as the prairie dog. |
The English word dog comes from Middle English dogge, from Old English docga, a "powerful dog breed". The term may derive from Proto-Germanic *dukkōn, represented in Old English finger-docce ("finger-muscle").
The word also shows the familiar petname diminutive -ga also seen in frogga "frog", picga "pig", stagga "stag", wicga "beetle, worm", among others. Due to the archaic structure of the word, the term dog may ultimately derive from the earliest layer of Proto-Indo-European vocabulary, reflecting the role of the dog as the earliest domesticated animal. |
Australian Aboriginal language Mbabaram is famous in linguistic circles for a striking coincidence in its vocabulary to English. When linguist R. M. W. Dixon began his study of the language by eliciting a few basic nouns among the first of these was the word for "dog" which coincidentally in Mbabaram is dog.
The Mbabaram word for "dog" really is pronounced almost identically to the English word (compare true cognates such as Yidiny gudaga, Dyirbal guda, Djabugay gurraa and Guugu Yimidhirr gudaa, for example).
The similarity is a complete coincidence: there is no discernible relationship between English and Mbabaram. This and other false cognates are often cited as a caution against deciding that languages are related based on a small number of comparisons.
The Mbabaram word for "dog" really is pronounced almost identically to the English word (compare true cognates such as Yidiny gudaga, Dyirbal guda, Djabugay gurraa and Guugu Yimidhirr gudaa, for example).
The similarity is a complete coincidence: there is no discernible relationship between English and Mbabaram. This and other false cognates are often cited as a caution against deciding that languages are related based on a small number of comparisons.
In 14th-century England, hound (from Old English: hund) was the general word for all domestic canines, and dog referred to a subtype of hound, a group including the mastiff. It is believed this "dog" type of "hound" was so common it eventually became the prototype of the category “hound”.
By the 16th century, dog had become the general word, and hound had begun to refer only to types used for hunting. Hound, cognate to German Hund,
Dutch hond, common Scandinavian hund, and Icelandic hundur, is ultimately derived from the Proto-Indo-European *kwon- "dog", found in Welsh ci (plural cwn), Latin canis, Greek kýōn, Lithuanian šuõ.
By the 16th century, dog had become the general word, and hound had begun to refer only to types used for hunting. Hound, cognate to German Hund,
Dutch hond, common Scandinavian hund, and Icelandic hundur, is ultimately derived from the Proto-Indo-European *kwon- "dog", found in Welsh ci (plural cwn), Latin canis, Greek kýōn, Lithuanian šuõ.
In breeding circles, a male canine is referred to as a dog, while a female is called a bitch (Middle English bicche, from Old English bicce, ultimately from Old Norse bikkja). A group of offspring is a litter. The father of a litter is called the sire, and the mother is called the dam.
Offspring are, in general, called pups or puppies, from French poupée, until they are about a year old. The process of birth is whelping, from the Old English word hwelp (cf. German Welpe, Dutch welp, Swedish valpa, Icelandic hvelpur).
Offspring are, in general, called pups or puppies, from French poupée, until they are about a year old. The process of birth is whelping, from the Old English word hwelp (cf. German Welpe, Dutch welp, Swedish valpa, Icelandic hvelpur).
History and evolution
History and evolution - Main articles: Origin of the domestic dog and Gray wolf. Domestic dogs inherited complex behaviors from their wolf ancestors, being pack hunters with complex body language.
These sophisticated forms of social cognition and communication may account for their trainability, playfulness, and ability to fit into human households and social situations, and these attributes have given dogs a relationship with humans that has enabled them to become one of the most successful species on the planet today.
These sophisticated forms of social cognition and communication may account for their trainability, playfulness, and ability to fit into human households and social situations, and these attributes have given dogs a relationship with humans that has enabled them to become one of the most successful species on the planet today.
Although experts largely disagree over the details of dog domestication, it is agreed that human interaction played a significant role in shaping the subspecies.
Shortly after domestication, dogs became ubiquitous in human populations, and spread throughout the world. Emigrants from Siberia likely crossed the Bering Strait with dogs in their company, and some experts suggest the use of sled dogs may have been critical to the success of the waves that entered North America roughly 12,000 years ago, although the earliest archaeological evidence of dog-like canids in North America dates from about 9,000 years ago.
Dogs were an important part of life for the Athabascan population in North America, and were their only domesticated animal.
Shortly after domestication, dogs became ubiquitous in human populations, and spread throughout the world. Emigrants from Siberia likely crossed the Bering Strait with dogs in their company, and some experts suggest the use of sled dogs may have been critical to the success of the waves that entered North America roughly 12,000 years ago, although the earliest archaeological evidence of dog-like canids in North America dates from about 9,000 years ago.
Dogs were an important part of life for the Athabascan population in North America, and were their only domesticated animal.
Dogs also carried much of the load in the migration of the Apache and Navajo tribes 1,400 years ago. Use of dogs as pack animals in these cultures often persisted after the introduction of the horse to North America.
The current consensus among biologists and archaeologists is that the dating of first domestication is indeterminate. There is conclusive evidence dogs genetically diverged from their wolf ancestors at least 15,000 years ago, but some believe domestication to have occurred earlier.
It is not known whether humans domesticated the wolf as such to initiate dog's divergence from its ancestors, or whether dog's evolutionary path had already taken a different course prior to domestication.
For example, it is hypothesized that some wolves gathered around the campsites of paleolithic camps to scavenge refuse, and associated evolutionary pressure developed that favored those who were less frightened by, and keener in approaching, humans.
The current consensus among biologists and archaeologists is that the dating of first domestication is indeterminate. There is conclusive evidence dogs genetically diverged from their wolf ancestors at least 15,000 years ago, but some believe domestication to have occurred earlier.
It is not known whether humans domesticated the wolf as such to initiate dog's divergence from its ancestors, or whether dog's evolutionary path had already taken a different course prior to domestication.
For example, it is hypothesized that some wolves gathered around the campsites of paleolithic camps to scavenge refuse, and associated evolutionary pressure developed that favored those who were less frightened by, and keener in approaching, humans.
The bulk of the scientific evidence for the evolution of the domestic dog stems from archaeological findings and mitochondrial DNA studies.
The divergence date of roughly 15,000 years ago is based in part on archaeological evidence that demonstrates the domestication of dogs occurred more than 15,000 years ago, and some genetic evidence indicates the domestication of dogs from their wolf ancestors began in the late Upper Paleolithic close to the Pleistocene/Holocene boundary, between 17,000 and 14,000 years ago. But there is a wide range of other, contradictory findings that make this issue controversial. |
Archaeological evidence suggests the latest dogs could have diverged from wolves was roughly 15,000 years ago, although it is possible they diverged much earlier.
In 2008, a team of international scientists released findings from an excavation at Goyet Cave in Belgium declaring a large, toothy canine existed 31,700 years ago and ate a diet of horse, musk ox and reindeer.
Prior to this Belgian discovery, the earliest dog fossils were two large skulls from Russia and a mandible from Germany dated from roughly 14,000 years ago. Remains of smaller dogs from Natufian cave deposits in the Middle East, including the earliest burial of a human being with a domestic dog, have been dated to around 10,000 to 12,000 years ago. There is a great deal of archaeological evidence for dogs throughout Europe and Asia around this period and through the next two thousand years (roughly 8,000 to 10,000 years ago), with fossils uncovered in Germany, the French Alps, and Iraq, and cave paintings in Turkey. The oldest remains of a domesticated dog in the Americas were found in Texas and have been dated to about 9,400 years ago - Source: Dog |
Recent studies
Dog history has been studied recently using mitochondrial DNA, which suggests that wolves and dogs split into different species around 100,000 years ago: but whether humans had anything to do with that, no one really knows.
Recent mtDNA analysis (Boyko et al.), suggests that the origin and location of dog domestication, long thought to be in east Asia, is in some doubt.
European Paleolithic Dogs - Part of the puzzle of the domestication of dogs lies in the Upper Paleolithic of Europe, beginning perhaps as long ago as 30,000 years.
Evidence of a Certain Domestication Partnership - A burial site in Germany called Bonn-Oberkassel has joint human and dog interments dated to 14,000 years ago.
The earliest "nobody-argues-about-it" domesticated dog was found in China at the early Neolithic (7000-5800 BC) Jiahu site in Henan Province.
European Mesolithic sites like Skateholm (5250-3700 BC) in Sweden have dog burials, proving the value of the furry beasts to hunter-gatherer settlements. Danger Cave in Utah is currently the earliest case of dog burial in the Americas, at about 11,000 years ago.
Recent mtDNA analysis (Boyko et al.), suggests that the origin and location of dog domestication, long thought to be in east Asia, is in some doubt.
European Paleolithic Dogs - Part of the puzzle of the domestication of dogs lies in the Upper Paleolithic of Europe, beginning perhaps as long ago as 30,000 years.
Evidence of a Certain Domestication Partnership - A burial site in Germany called Bonn-Oberkassel has joint human and dog interments dated to 14,000 years ago.
The earliest "nobody-argues-about-it" domesticated dog was found in China at the early Neolithic (7000-5800 BC) Jiahu site in Henan Province.
European Mesolithic sites like Skateholm (5250-3700 BC) in Sweden have dog burials, proving the value of the furry beasts to hunter-gatherer settlements. Danger Cave in Utah is currently the earliest case of dog burial in the Americas, at about 11,000 years ago.
Dogs as Persons - A reanalysis (Losey and colleagues 2011) of dog burials dated to the Late Mesolithic-Early Neolithic Kitoi period in the Cis-Baikal region of Siberia suggests that in some cases, dogs were awarded "person-hood" and treated equal to fellow humans.
A dog burial at the Shamanka site was of a male, middle-aged dog (probably a husky) which had suffered injuries to its spine, injuries from which it recovered. The burial, radiocarbon dated to ~6200 years ago (cal BP), was interred in a formal cemetery, and in a similar manner to the humans within that cemetery. Losey and colleagues believe the dog may have lived with its human family at Shamanaka.
A dog burial at the Shamanka site was of a male, middle-aged dog (probably a husky) which had suffered injuries to its spine, injuries from which it recovered. The burial, radiocarbon dated to ~6200 years ago (cal BP), was interred in a formal cemetery, and in a similar manner to the humans within that cemetery. Losey and colleagues believe the dog may have lived with its human family at Shamanaka.
A wolf burial at the Lokomotiv-Raisovet cemetery (~7300 cal BP) was also an older adult male.
The wolf's diet (from stable isotope analysis) was ungulates, and although its teeth were worn, there is no direct evidence that this wolf was part of the community. Nevertheless, it too was buried in a formal cemetery.
These burials are exceptions, but not that rare: there are others, but there is also is evidence that people of the Kitoi culture (late Mesolithic fisher-hunters in Baikal) consumed dogs and wolves, as their burned and fragmented bones appear in refuse pits.
Losey and associates suggest that these are indications that Kitoi hunter-gatherers considered that at least these individual dogs were "persons".
Haplotypes and Grey Wolves - A recent study led by Robert Wayne (vonHoldt et al., below) at UCLA and appearing in Nature in March 2010 reported that dogs appear to have a higher proportion of wolf haplotypes from grey wolves native to the Middle East.
That suggests, contrary to earlier studies, that the middle east was the original location of domestication. What also showed up in this report was evidence for either a second Asian domestication or a later admixture with Chinese wolves.
The wolf's diet (from stable isotope analysis) was ungulates, and although its teeth were worn, there is no direct evidence that this wolf was part of the community. Nevertheless, it too was buried in a formal cemetery.
These burials are exceptions, but not that rare: there are others, but there is also is evidence that people of the Kitoi culture (late Mesolithic fisher-hunters in Baikal) consumed dogs and wolves, as their burned and fragmented bones appear in refuse pits.
Losey and associates suggest that these are indications that Kitoi hunter-gatherers considered that at least these individual dogs were "persons".
Haplotypes and Grey Wolves - A recent study led by Robert Wayne (vonHoldt et al., below) at UCLA and appearing in Nature in March 2010 reported that dogs appear to have a higher proportion of wolf haplotypes from grey wolves native to the Middle East.
That suggests, contrary to earlier studies, that the middle east was the original location of domestication. What also showed up in this report was evidence for either a second Asian domestication or a later admixture with Chinese wolves.
Dog History - When Were Dogs Domesticated? - It seems clear that dog domestication was a long process, which started far longer ago than was believed even as recently as 2008.
Based on evidence from Goyet Cave in Belgium, Chauvet cave in France, and Predmosti in Czech Republic, the dog domestication process probably began as long ago as 35,000 years, although the oldest evidence for a broader relationship, a working relationship, is at the Bonn-Oberkassel site, 14,000 years ago.
The story of dog domestication is still in transition itself. Evidence for the appearance of breed variation is found in several European Upper Paleolithic sites.
Based on evidence from Goyet Cave in Belgium, Chauvet cave in France, and Predmosti in Czech Republic, the dog domestication process probably began as long ago as 35,000 years, although the oldest evidence for a broader relationship, a working relationship, is at the Bonn-Oberkassel site, 14,000 years ago.
The story of dog domestication is still in transition itself. Evidence for the appearance of breed variation is found in several European Upper Paleolithic sites.
Medium-sized dogs (with wither heights between 45-60 cm) have been identified in Natufian sites in the Near East (Tell Mureybet in Syria, Hayonim Terrace and Ein Mallaha in Israel, and Pelagawra Cave in Iraq) dated to ~15,500-11,000 cal BP).
Medium to large dogs (wither heights above 60 cm) have been identified in Germany (Kniegrotte), Russia (Eliseevichi I) and Ukraine (Mezin), ~17,000-13,000 cal BP).
Small dogs (wither heights under 45 cm) have been identified in Germany (Oberkassel, Teufelsbrucke and Oelknitz), Switzerland (Hauterive-Champreveyres), France (Saint-Thibaud-de-Couz, Pont d'Ambon) and Spain (Erralia) between ~15,000-12,300 cal BP. See Pionnier-Capitan et al for more information.
Medium to large dogs (wither heights above 60 cm) have been identified in Germany (Kniegrotte), Russia (Eliseevichi I) and Ukraine (Mezin), ~17,000-13,000 cal BP).
Small dogs (wither heights under 45 cm) have been identified in Germany (Oberkassel, Teufelsbrucke and Oelknitz), Switzerland (Hauterive-Champreveyres), France (Saint-Thibaud-de-Couz, Pont d'Ambon) and Spain (Erralia) between ~15,000-12,300 cal BP. See Pionnier-Capitan et al for more information.
Modern Breeds and Ancient Origins - A recent study of pieces of DNA called SNPs (single-nucleotide polymorphism) which have been identified as markers for modern dog breeds published in 2012 (Larson et al) comes to some surprising conclusions: that despite the clear evidence for marked size differentiation in very early dogs (e.g., small, medium and large dogs found at Svaerdborg), this has nothing to do with current dog breeds.
The oldest modern dog breeds are no more than 500 years old, and most date only from ~150 years ago.
Source: Dog history - with links
The oldest modern dog breeds are no more than 500 years old, and most date only from ~150 years ago.
Source: Dog history - with links
Credible theory
Studies conducted on Russian fox farms may reveal the answer. In the 1950s, Russian scientist Dmitri Belyaev began selectively breeding captive silver foxes on a fur farm with the idea of making them tamer and easier to handle.
He carefully chose foxes that were more tolerant of humans than the rest. Over a few generations of breeding, the foxes became tamer.
However, they also developed strange coat colors and other odd characteristics, such as floppy ears and curly tails. Belyaev's new foxes barked more, and the females came into heat more often and younger than their ancestors.
In fact, Belyaev's foxes had exactly the same kinds of qualities we see in dogs, but never in wolves. Why should selecting for tamer animals also create individuals with all these unusual physical qualities?
He carefully chose foxes that were more tolerant of humans than the rest. Over a few generations of breeding, the foxes became tamer.
However, they also developed strange coat colors and other odd characteristics, such as floppy ears and curly tails. Belyaev's new foxes barked more, and the females came into heat more often and younger than their ancestors.
In fact, Belyaev's foxes had exactly the same kinds of qualities we see in dogs, but never in wolves. Why should selecting for tamer animals also create individuals with all these unusual physical qualities?
The theory is that by selecting for individuals that are friendlier and less suspicious of humans, you also affect some aspects of the developmental process. You're breeding animals that are more puppy-like in their behavior.
Linked to the genes that control this extended puppyhood are other genes that affect coat color.
In addition, when you lengthen the amount of time behavioral development takes, you disrupt some other types of development.
Based on the research on foxes, the natural selective pressure on village wolves to be tamer might have simultaneously created a population of wolves with all kinds of odd characteristics. Now you have a group of animals that are smaller and friendlier than wolves and that come in lots of colors.
This is the point at which researchers like the Coppingers say that humans began adopting puppies and favoring some attributes over others, using artificial selection to create different types of dogs.
Linked to the genes that control this extended puppyhood are other genes that affect coat color.
In addition, when you lengthen the amount of time behavioral development takes, you disrupt some other types of development.
Based on the research on foxes, the natural selective pressure on village wolves to be tamer might have simultaneously created a population of wolves with all kinds of odd characteristics. Now you have a group of animals that are smaller and friendlier than wolves and that come in lots of colors.
This is the point at which researchers like the Coppingers say that humans began adopting puppies and favoring some attributes over others, using artificial selection to create different types of dogs.
The theory that early selective breeding has produced dogs that stay in a puppy stage - even though sexual maturity and adult behavior persists - could very well be true, and fits well into the modern dog's behavior.
You could say that the dog remains in a needy stage - we act as parents and give the dog food and care. This theory could also fit into the domesticated cat certain behavioral patterns.
Photo: The true suffering - constant search for human closeness and food – an abandoned dog seeking always back to human closeness. Because of the domestication, they are forced into this in order to survive.
You could say that the dog remains in a needy stage - we act as parents and give the dog food and care. This theory could also fit into the domesticated cat certain behavioral patterns.
Photo: The true suffering - constant search for human closeness and food – an abandoned dog seeking always back to human closeness. Because of the domestication, they are forced into this in order to survive.
A dog is not able to survive without a man's protection, food and vicinity - the domestication is inherited over tens of thousands years and the domestic dog has a predisposition to exhibit a social intelligence that is uncommon in the animal world. It takes six generations (48 years) for a dog to become feral, so that he is able to hunt naturally – to abandon a dog is animal cruelty.