The Domestic Dog: Origins and Evolution

The domestic dog is one of the most beloved and versatile animals on the planet. They originated from wolves, specifically from the gray wolf species, around 15,000 to 30,000 years ago.

Their ancestors were likely attracted to human camps and settlements, where they scavenged for food and eventually learned to coexist with humans. The first dogs were probably kept for tasks such as hunting and guarding.

The process of domestication was likely a gradual one, with humans and wolves interacting and adapting to each other over time. This led to the development of different breeds and types of dogs, each with their unique characteristics and abilities.

Domestic dogs have since become an integral part of human society, serving as companions, workers, and even therapy animals.

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The earliest remains of a domesticated dog were discovered in Bonn-Oberkassel, Germany, dating back to 14,223 years ago. This dog was buried along with a man and a woman, all three having been sprayed with red hematite powder and buried under large, thick basalt blocks.

DNA sequences show that all ancient and modern dogs share a common ancestry and descended from an ancient, extinct wolf population. This wolf population was distinct from any modern wolf lineage.

Genetic studies suggest that the domestication process of dogs commenced over 25,000 years ago, in one or several wolf populations in either Europe, the high Arctic, or eastern Asia.

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The earliest remains of a domesticated dog were discovered in Bonn-Oberkassel, Germany, dating back to 14,223 years ago.

These remains show that the dog was not a local wolf, but rather a distinct species that had been domesticated. The dog was buried along with a man and a woman, all three having been sprayed with red hematite powder and buried under large, thick basalt blocks.

The dog's death was caused by canine distemper, and its presence suggests that dogs were domesticated before the advent of agriculture. This timing is significant, as it predates the domestication of other animals.

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DNA sequences show that all ancient and modern dogs share a common ancestry, descending from an extinct wolf population that was distinct from any modern wolf lineage. Some studies suggest that dogs are more closely related to modern Eurasian wolves than to American wolves.

Genetic studies suggest that the domestication process began over 25,000 years ago, in one or several wolf populations in Europe, the high Arctic, or eastern Asia. The exact location of the first domestication remains uncertain.

A study in 2018 identified 429 genes that differed between modern dogs and modern wolves, which are linked to neural crest and central nervous system development.

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The journey from wild animal to beloved pet is a remarkable one. Wolves, the ancestors of domesticated dogs, were once solitary hunters that roamed the earth.

Their pack dynamics laid the foundation for the social structures we see in dogs today. In fact, studies have shown that domesticated dogs still exhibit pack behavior, such as dominance hierarchies and cooperative hunting.

The process of domestication began around 15,000 years ago when humans first started keeping wolves as companions. These early wolves were likely attracted to human camps for food scraps.

Over time, humans and wolves formed a mutually beneficial relationship, with humans providing food and wolves offering companionship and protection. This partnership ultimately led to the development of the first domesticated dogs.

The earliest archaeological evidence of dog domestication comes from a site in Germany, where the remains of dogs have been found dating back to around 14,200 years ago.

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Dogs come in all shapes and sizes, ranging from the massive Great Dane to the tiny Chihuahua.

The dog's skeleton is well adapted for running, with vertebrae on the neck and back that have extensions for back muscles, and long ribs that provide room for the heart and lungs.

Some breeds have naturally short tails, with as few as three vertebrae, while others have their tails attached to the skeleton.

The dog's skull has identical components regardless of breed type, but there is significant divergence in terms of skull shape between types, with three basic skull shapes: dolichocephalic, mesocephalic, and brachycephalic.

Dogs have around 42 teeth in their jaw, which has evolved for the consumption of flesh, and they use their carnassial teeth to cut food into bite-sized chunks.

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Dogs come in a wide range of sizes, from the massive Great Dane to the tiny Chihuahua. The largest dogs can weigh up to 79 kg (174 lb) and reach a height of 81 cm (32 in), while the smallest dogs can weigh as little as 0.5 kg (1.1 lb) and stand at just 13 cm (5.1 in) tall.

The number of bones in a dog's skeleton remains the same, regardless of their size, with the exception of the tail. However, the skeletal structure of dogs has undergone significant changes through selective breeding, resulting in larger or smaller skeletons depending on the breed.

Dogs have a well-adapted skeleton for running, with vertebrae that have extensions for back muscles and long ribs that provide room for the heart and lungs. The shoulders are also unattached to the skeleton, allowing for flexibility.

The dog's skull has identical components, but its shape can vary significantly between breeds, with three main types: dolichocephalic, mesocephalic, and brachycephalic.

Here are the three basic skull shapes found in dogs:

Dogs have 42 teeth in their jaw, which have evolved for the consumption of flesh. They use their carnassial teeth to cut food into bite-sized chunks, especially meat.

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Dogs have two main types of coats: double coats, common in breeds from colder climates, and single coats, which only have a topcoat.

Double coats are made up of a coarse guard hair and a soft down hair, providing extra warmth and protection.

Some breeds have a thick corded coat, while others are completely hairless.

Premature graying can occur in dogs as early as one year of age, often associated with impulsive behaviors, anxiety, and fear of unfamiliar things.

Breeds like the Yorkshire Terrier are often groomed to a specific style, such as the "show cut" that's characteristic of their breed.

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A dog's tail is the terminal appendage of the vertebral column, made up of a string of 5 to 23 vertebrae enclosed in muscles and skin that support the dog's back extensor muscles.

Dogs can use their tails to communicate their emotional state, and the tail also helps the dog maintain balance by putting its weight on the opposite side of the dog's tilt.

Dogs can injure themselves by wagging their tails forcefully, a condition known as kennel tail, happy tail, bleeding tail, or splitting tail.

The violet gland, also known as the supracaudal gland, is characterized by sebaceous glands on the dorsal surface of a dog's tail, and in some breeds, it may be vestigial or absent.

A study suggests that dogs show asymmetric tail-wagging responses to different emotive stimuli, with higher amplitude of tail-wagging movements to the right side associated with stimuli that could be expected to elicit approach tendencies.

Some dogs can be born without tails because of a DNA variant in the T gene, which can also result in a congenitally short (bobtail) tail.

Dogs sniff other dogs' rear ends to gather chemical information that helps them identify each dog as an individual. This unique scent profile can reveal a dog's genetic makeup, reproductive status, diet, and emotional state.

A dog's scent is made up of a unique combination of smells from gland-lined sacs on either side of their anus. Each dog's scent is like a fingerprint, making it possible for them to recognize one another.

Sniffing is a vital way for dogs to communicate and gather information about their environment. It's not just about identifying other dogs, but also about understanding their surroundings.

Dogs can acquire a wide range of health issues, including heart diseases, gastrointestinal problems, and respiratory diseases.

Dogs are also prone to various parasites, such as lice, fleas, and ticks, which can lead to infections and other health problems.

Neoplasia is the most common cause of death for dogs, followed by heart and renal failure.

Dogs can also be a source of zoonoses, or diseases that can be transmitted to humans, including rabies, hydatid disease, and leptospirosis.

Studies have shown that having a dog can have health benefits for their owners, including reduced stress and anxiety, and increased physical activity.

Dogs can also provide social support, helping their owners to feel less lonely and isolated.

Research has also found that children who live with pets, including dogs, have fewer absences from school due to illness.

Dogs can acquire a wide range of health issues, including upper respiratory tract diseases, heart diseases, gastrointestinal disease, and neoplasia, which is the most common cause of death for dogs.

Many of these health issues can be prevented or managed with proper care and attention. For example, regular vaccinations can help protect against diseases like canine adenovirus, canine distemper virus, and canine parvovirus.

Dogs are also prone to parasites like lice, fleas, and ticks, which can cause discomfort and transmit diseases. Regular grooming and parasite control measures can help prevent infestations.

In addition to these health issues, dogs can also be exposed to toxins and poisonous substances, which can be fatal if not treated promptly. The most common substances involved in dog poisonings are pharmaceuticals, toxic foods, and rodenticides.

It's essential to keep toxic substances out of reach of your furry friends and to be aware of the signs of poisoning, such as vomiting, diarrhea, and lethargy. If you suspect your dog has ingested something toxic, seek veterinary attention immediately.

Dogs can also be a source of health risks for humans, particularly through the transmission of diseases like rabies. According to the World Health Organization, 59,000 people died from rabies in 2018, with dogs being the most significant vector.

To protect yourself and your loved ones from dog-borne diseases, make sure to keep your dog up-to-date on vaccinations and to wash your hands regularly after handling your dog or its waste.

The lifespan of dogs can vary significantly depending on their breed and size. On average, a dog's median longevity is around 12.7 years.

Obesity is a major factor in reducing a dog's lifespan, with obese dogs living approximately a year and a half less than their healthy-weight counterparts. This is a stark reminder of the importance of maintaining a healthy weight.

Interestingly, a 2024 UK study found that purebred dogs actually live longer than crossbred dogs, which challenges the previous notion that crossbred dogs have higher life expectancies. This study included "designer dogs" as crossbred, and noted that purebred dogs often receive better care.

Small dogs with longer muzzles tend to live longer than larger medium-sized dogs with shorter muzzles. This is just one example of how a dog's physical characteristics can impact their lifespan.

Inbreeding depression is a serious concern for dog breeders and owners alike. It's a phenomenon where breeding dogs that are too closely related can lead to a range of health problems.

Inbreeding decreases litter size and survival, as seen in studies of seven dog breeds, including the Bernese Mountain Dog and the Cairn Terrier. This means that litters may be smaller than expected, and some puppies may not survive to adulthood.

The data on 42,855 Dachshund litters shows a clear correlation between inbreeding and increased stillbirth rates. As the inbreeding coefficient increases, the percentage of stillborn puppies also increases.

Mortality due to infection is another significant concern in inbred litters. In a study of Boxer litters, 22% of puppies died before reaching 7 weeks of age, with infection being a major cause of death.

Domestic dogs are incredibly attuned to human behavior and have acquired the ability to understand and communicate with us.

Their behavior has been shaped by millennia of contact with humans, and they've developed unique social-cognitive skills that are parallel to those of children.

Research has shown that only 11 fixed genes vary between wolves and dogs, indicating the occurrence of artificial selection and the subsequent divergence of behavior and anatomical features.

These gene variations affect the catecholamine synthesis pathway, leading to traits such as high sociability and a lack of fear in dogs.

However, some dogs can become aggressive due to trauma or abuse, fear or anxiety, territorial protection, or protecting an item they consider valuable.

Dogs have a natural instinct called prey drive, which can be influenced by breeding and drive them to consider objects or other animals as prey.

Some breeds have been enhanced to hunt and kill vermin or other pests, and puppies or dogs may engage in coprophagy due to habit, stress, or boredom.

Most dogs can swim, with around 63.5% of dogs able to swim without a trainer in a swimming pool.

A study found a correlation between swimming and 'improvement' of the hip osteoarthritis joint in dogs.

Dogs demonstrate a theory of mind by engaging in deception, and some studies suggest that they have a visual sense for number.

However, dogs may lack spatial memory, as one study found that dogs could not distinguish food bowls at specific locations without distinguishing cues.

Here are some key behaviors exhibited by domestic dogs:

Dogs' sense of smell is incredibly powerful, with some breeds having up to 300 million smell-sensitive receptors, roughly forty times more than humans.

Their sense of hearing is also impressive, with some dogs able to pick up sounds from as far as 400 meters away, four times greater than humans.

Dogs can feel small variations in the Earth's magnetic field, which can influence their behavior, such as preferring to defecate with their spines aligned in a north-south position.

Their vision is dichromatic, meaning they see the world in shades of yellow, blue, and gray, with difficulty differentiating between red and green.

The fovea centralis area of the dog's eye is attached to a nerve fiber, making it the most sensitive to photons.

Dogs' visual acuity is up to 8 times less effective than a human, and their ability to discriminate levels of brightness is about two times worse.

Their stiff, deeply embedded hairs, or whiskers, sense atmospheric changes, vibrations, and objects not visible in low light conditions, helping them navigate their surroundings.

Dogs have been shaped by millennia of contact with humans, allowing them to understand and communicate with humans in a unique way.

Their behavior is influenced by selective breeding for desirable traits, with only 11 fixed genes showing variation between wolves and dogs. These gene variations affect the catecholamine synthesis pathway, influencing the fight-or-flight response and emotional processing.

Dogs tend to be less timid and less aggressive than their wolf counterparts, but some breeds may exhibit aggression due to genetic modifications.

Some dogs may become aggressive due to trauma or abuse, fear or anxiety, territorial protection, or protecting an item they consider valuable.

Dogs have a natural instinct called prey drive, which can be influenced by breeding and drive them to consider objects or other animals as prey.

A study found that around 36.5% of dogs cannot swim, but the other 63.5% can swim without a trainer in a swimming pool.

Dogs can exhibit a range of behaviors related to determining their position in the social hierarchy and their mood, including postures that reveal their states of mind.

Here are some key behaviors exhibited by dogs:

Dogs can be active at any time of day or night, and feral domestic dogs maintain home ranges that they defend against others.

Dogs can learn by inference, a process where they figure out new information based on what they already know. This was demonstrated in a study with Rico, a Border Collie, who learned the labels of over 200 items and correctly retrieved new items after four weeks.

Chaser, another Border Collie, learned over 1,000 words, including their names and how to associate them with verbal commands. This impressive vocabulary is a testament to their ability to learn and understand complex information.

Dogs' cognitive abilities are surprisingly similar to those of horses, chimpanzees, and cats. However, one study found that dogs lack spatial memory, unable to distinguish food bowls at specific locations without visual cues.

Dogs have a unique visual sense for number, with a ratio-dependent activation for numerical values from 1-3 to larger than four. This means they can understand basic math concepts, even if they can't perform complex calculations.

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Coyotes and big cats like leopards have been known to attack dogs, and leopards even prefer them.

In fact, leopards have been recorded to kill and consume dogs of any size.

Siberian tigers in the Amur river region have also killed dogs in the middle of villages, showing that they don't tolerate wolves as competitors.

Dogs are omnivores, which means they eat both plants and animals.

Dogs from agricultural societies have extra copies of genes that help them digest starch, giving them an advantage on a starch-rich diet.

Coyotes and big cats have also been known to attack dogs. In particular, leopards are known to have a preference for dogs and have been recorded to kill and consume them, no matter their size.

Leopards have a unique relationship with dogs in their territory. They view dogs as potential competitors and threats.

Siberian tigers in the Amur river region have killed dogs in the middle of villages, showing no tolerance for canine presence.

Striped hyenas are known to kill dogs in their range, adding to the list of predators that view dogs as prey.

Dogs are typically described as omnivores, meaning they can thrive on a diet that includes both plants and animals.

Some dog breeds produce amylase in their saliva, which helps them digest starch-rich foods.

Dogs can't produce bile acid with taurine on their own, so they need to get it from other animals.

They also can't synthesize ten of the twenty-one amino acids common to all life forms, including arginine, which is essential for maintaining nitrogen balance.

Dogs require arginine to stay healthy, just like cats do.

Their nutritional needs place them somewhere in between carnivores and omnivores.

Dogs must get their vitamin D from consuming other animals, unlike humans who can produce it themselves.

This means dog owners need to make sure their pets are getting a balanced diet that includes animal-based foods.

The range of a species refers to the geographic area where it can be found. This can vary greatly depending on the species, with some having a very limited range and others covering vast territories.

Some species, like the polar bear, have a circumpolar range, meaning they can be found in the Arctic Circle. Their range is determined by the availability of their primary food source, seals.

The range of a species can also be influenced by climate and habitat. For example, the mountain lion has a range that spans across western North America, from British Columbia to central Mexico.

In some cases, the range of a species can be fragmented, with isolated populations found in different areas. This is often due to human activities such as deforestation and urbanization.

The range of a species can have a significant impact on its ecology and diet. For instance, the African elephant's range is determined by the availability of its primary food source, grasses and plants.

In the wild, the range of a species can also be affected by natural disasters such as droughts and wildfires.

Dogs can be a significant health risk to humans, particularly in terms of the spread of diseases like rabies, which is responsible for 59,000 deaths globally each year. Dog bites can also lead to serious injuries and infections.

In the United States, cats and dogs are a factor in more than 86,000 falls each year, with children being the primary victims. Sharp claws can lacerate flesh and cause serious infections.

However, dogs can also have numerous health benefits for humans, including reducing anxiety and stress, and even protecting against allergies and autoimmune diseases. Studies have shown that people who own dogs tend to take more physical exercise and have lower blood pressure than those who don't own dogs.

Dogs can carry a range of diseases that can be transmitted to humans, including rabies, which is responsible for 99% of global cases.

Rabies is a significant health risk, with 59,000 people dying from it globally in 2018, with the majority of deaths occurring in Asia and Africa.

Dog bites can be serious, with tens of millions of people affected each year, and children are the primary victims, often sustaining more serious injuries.

Sharp claws can cause lacerations and serious infections, and dog bites are a leading cause of falls, with over 86,000 incidents reported in the United States each year.

Dog feces can contain toxic eggs from the dog roundworm, Toxocara canis, which can cause toxocariasis in humans, with around 10,000 cases reported in the United States each year.

Untreated toxocariasis can lead to retinal damage and decreased vision, and hookworms in dog feces can cause cutaneous larva migrans in humans.

Dogs can also carry other diseases, such as canine adenovirus, canine distemper virus, and canine parvovirus, which can be transmitted to humans through contact with infected dogs or contaminated surfaces.

Many common household products, including cleaning products, can be toxic to dogs if ingested, and it's essential to keep these products out of reach of your furry friends.

The most common causes of death in dogs are neoplasia, heart and renal failure, and their pathology and treatment outcomes are similar to those in humans.

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Research suggests that having a dog can lead to increased physical activity, with dog owners taking more exercise than those without pets or with cats. This can be a great motivator for those who struggle to get moving.

Studies have found that pet guardianship is associated with increased survival in cases of coronary artery disease, and human guardians are less likely to die within a year of an acute myocardial infarction than those who don't own dogs. This is a significant health benefit.

Pet ownership has been linked to reduced hospital visits and a lower likelihood of being on medication for heart problems and sleeping difficulties. This is likely due to the increased physical activity and social support that comes with having a pet.

Having a dog can also reduce anxiety, with people showing reductions in cardiovascular, behavioral, and psychological indicators of anxiety when in a dog's presence. This is a great benefit for those who struggle with anxiety.

Research has pointed to significantly less absenteeism from school through sickness among children who live with pets. This is a positive outcome for families and schools alike.

Dog ownership can also lead to increased social interactions, with wheelchair-users experiencing more positive interactions with strangers when accompanied by a dog. This is a great benefit for those who struggle to connect with others.

Having a pet can also make people more inclined to foster positive relationships with their neighbors, as seen in a 2015 study. This is a great way to build a stronger community.

Genetic diseases are caused by mutations in DNA, which can be inherited from parents or occur spontaneously.

The Human Genome Project revealed that we each have about 3 billion base pairs of DNA, and it's estimated that each person has about 100 genetic mutations.

Some genetic diseases are recessive, meaning a person needs to inherit two copies of the mutated gene, one from each parent, to express the disease.

Genetic diseases can be complex, with multiple genes contributing to the condition, as seen in the case of sickle cell anemia.

In some cases, genetic diseases can be prevented or treated with genetic testing and counseling, as well as advances in gene therapy.

Genetic diseases can affect anyone, regardless of age, sex, or ethnic background, making them a significant public health concern.

Genetic diseases are often chronic and can have a significant impact on a person's quality of life, affecting not just the individual but also their family and caregivers.

Genetic diseases can be inherited in an autosomal dominant or autosomal recessive pattern, with some diseases showing a sex-linked inheritance pattern.

Dogs need their first series of shots when they're six weeks old. This series consists of four doses of combined vaccines against distemper, hepatitis, parainfluenza, and parvovirus, given two to four weeks apart.

A booster shot is given within one year of the initial series, and then again every three years. This helps keep your furry friend protected against these diseases.

At three months old, dogs can receive their first rabies vaccine, which is readministered every year or every three years.

Dogs have been a symbol of guidance, protection, loyalty, and love in various cultures throughout history. In ancient Mesopotamia, dogs were associated with the goddess of healing and medicine, Ninisina.

Dogs were also seen as emblems of magical protection in the Neo-Assyrian and Neo-Babylonian periods. In China, Korea, and Japan, dogs are viewed as kind protectors.

In mythology, dogs often appear as pets or watchdogs, guarding the gates of the underworld in various Indo-European mythologies. Cerberus, a three-headed, dragon-tailed watchdog, guards the gates of Hades in Greek mythology.

Dogs feature in association with the Greek goddess Hecate and in Norse mythology, a dog called Garmr guards Hel, a realm of the dead. In Welsh mythology, Cŵn Annwn guards Annwn.

Dogs have also been associated with gods and goddesses in Hindu mythology, including Yama, the god of death, who owns two watchdogs named Shyama and Sharvara. A black dog is considered to be the vahana (vehicle) of Bhairava (an incarnation of Shiva).

In Christianity, dogs represent faithfulness, and the Dominican Order is nicknamed "dog of the Lord" or "hound of the Lord" due to a dream of Saint Dominic's mother.

Domestic dogs have undergone significant genetic changes since their ancestors, the gray wolves, diverged around 15,000 to 30,000 years ago.

Their genetic makeup has been shaped by thousands of years of artificial selection, where humans have selectively bred dogs for desirable traits such as smaller size, floppy ears, and a variety of coat types.

The domestic dog's genetic diversity is relatively low compared to other mammals, likely due to their widespread domestication and breeding practices.

Taxonomy is the science of classifying living things, and when it comes to dogs, it can get pretty complicated. Dogs are classified as a subspecies of Canis lupus, along with wolves and dingoes.

The domestic dog, gray wolf, and golden jackal were all classified as part of the genus Canis by Carl Linnaeus in 1758. He even gave them their own species names, with the domestic dog being Canis familiaris and the gray wolf being Canis lupus.

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The classification of dingoes is a bit of a gray area, with some considering them to be a separate species and others as a feral Canis familiaris. This dispute is due in part to the fact that dingoes are descended from domestic dogs that were introduced to Australia thousands of years ago.

Here's a rough timeline of the divergence of some of the Canidae family members:

As you can see, the gray wolf and domestic dog diverged from a common ancestor around 1.10 million years ago. This is just a small sample of the many species within the Canidae family, but it gives you an idea of just how complex their taxonomy can be.

Dogs cluster together tightly in a two-dimensional space when their genotypes are analyzed using principle component analysis (PCA). This is in contrast to wolves, which show a more scattered distribution.

The distribution of dogs among themselves reveals a clear East-West gradient, with southern East Asia, Europe, and Africa forming three major geographic axes. The northern Chinese indigenous dogs and dog breeds from the Middle East/Arctic regions/Tibet fall between these three extremes.

Dogs from southern China and several East Asian breeds, such as the Chow Chow and Akita, are found to be closest to wolves. This is based on combining the current dataset with data from a previous SNP array study.

East Asian dogs are the most basal lineages connecting to gray wolves, as seen in the phylogenetic relationships among the 58 samples analyzed.

The time of divergence between contemporary wolves and dogs is estimated to be around 33,000 years ago. This is based on joint allele frequencies between gray wolves and southern Chinese indigenous dogs.

A population of 4,600 individuals is thought to have given rise to the domestic dog lineage, which expanded to about 17,500 individuals around the time of divergence. This is a significant increase in population size.

The wolf population, on the other hand, experienced a very mild population growth, with a 1.26-fold increase starting around 290,000 years ago. This growth was likely a gradual process.

The migration rate from the dog lineage to the wolf lineage is estimated to be 0.97, while the migration rate in the other direction is inferred to be 5.02. This suggests a clear asymmetry in the migration rates between the two populations.

Multiple levels of genetic information support an ancient split between dogs and wolves, including joint site frequencies and sequence divergence. This suggests that the divergence between the two species is an ancient event.

A total of 58 canids from around the world were gathered for this study, including 12 gray wolves from across the Eurasian continent.

These canids were collected from diverse geographic regions, such as southern East Asia, northern East Asia, Africa, and the Americas.

The study included 11 indigenous dogs from southern East Asia and 12 indigenous dogs from northern East Asia, as well as 4 village dogs from Africa.

A set of 19 diverse dog breeds was also included, distributed across the Old World and the Americas, such as the Afghan Hound, Sloughi, and Tibetan Mastiff.

Individual genomes were sequenced to an average of 15× coverage, which is a significant amount of data.

The DNA sequence analysis was done using the Genome Analysis Toolkit, and after stringent filtering, 20,353,184 SNPs and 3,856,246 small indels were identified.

Most of these genetic variations are shared between groups, such as wolves, indigenous dogs, and dog breeds, reflecting their recent divergence.

The sequencing strategy was highly sensitive, with a false negative rate around 10% and less than 5% false positives.

To estimate the mutation rate from species comparisons, researchers use data from multiple species alignments. These alignments are downloaded from the Ensembl database.

Human is often used as the outgroup in these comparisons, and a second species like cat, horse, or cattle is chosen as the sister species to the dog.

The researcher then extracts information from the multiple species alignments to do a three species comparison: human, dog, and the sister species.

Branch lengths along the dog lineage are estimated using the baseml package from the PAML package.

The long-term evolutionary rate along the dog lineage is calculated by dividing the branch length by the divergence time between the sister species and the dog.

The domestic dog's history is a fascinating topic. The dog's out of southern East Asia history dates back around 15,000 years ago.

This event occurred before the origin of agriculture, indicating that dogs were already an established part of human society at that time. The radiation of dogs out of southern East Asia likely followed existing human settlements.

By around 10,000 years ago, the out of southern East Asia lineage had spread to the Middle East/Africa and arrived in Europe. One of the lineages migrated back to northern China, meeting endemic Asian lineages that had spread from southern East Asia.

Domestic dogs typically reach sexual maturity between six months to one year of age, although larger breeds may take up to two years to mature.

Their reproductive cycle is characterized by four stages: anestrus, proestrus, estrus, and diestrus. The anestrus period lasts about 2 to 4 months.

Female dogs will experience their first estrous cycle around six months to one year of age, marked by their vulvas swelling and producing discharges, usually lasting between 4 and 20 days.

During estrus, females become mentally and physically receptive to copulation and can be fertilized by multiple males within a week after ovulation.

An average litter consists of about six puppies, although litter sizes can vary depending on the breed and nutritional status of the mother.

Domestic dogs can reproduce at approximately six-month intervals, although this can be less frequent in practice.

Here's a breakdown of the reproductive cycle:

Females nurse and care for their puppies until they are weaned at about 8 to 10 weeks of age, while males typically reach puberty between six months to one year of age.

Exploring your ancestry can be a fascinating journey, and understanding its significance can help you appreciate your heritage.

Many people discover their ancestors were skilled craftsmen, farmers, or traders, which influenced the development of their communities.

Your ancestors may have been part of a nomadic tribe, traveling from place to place in search of resources.

Their paths often crossed with other groups, leading to cultural exchange and the formation of new traditions.

Some ancestors may have been part of a royal family, holding positions of power and shaping the course of history.

The customs and practices of your ancestors can still be seen in modern-day celebrations and festivals.

You may find that your ancestors were known for their bravery in battle, defending their lands against invaders.

Their legacy lives on in the stories and myths passed down through generations.

The history of the domestic dog is a fascinating story that spans thousands of years. The earliest remains of a domesticated dog were discovered in Bonn-Oberkassel, Germany, and date back to 14,223 years ago.

Domestication is believed to have occurred in the time of hunter-gatherers, predating agriculture. The dog was found buried along with a man and a woman, all three having been sprayed with red hematite powder and buried under large, thick basalt blocks.

The dog had died of canine distemper, but its significance lies in its status as the first species to be domesticated. This timing suggests that dogs were domesticated independently of agriculture.

DNA sequences show that all ancient and modern dogs share a common ancestry and descended from an ancient, extinct wolf population. This population was distinct from any modern wolf lineage.

The dog is a domestic animal that likely travelled a commensal pathway into domestication, meaning it neither benefited nor got harmed. The questions of when and where dogs were first domesticated remain uncertain.

Genetic studies suggest a domestication process commencing over 25,000 years ago, in one or several wolf populations in either Europe, the high Arctic, or eastern Asia.

Domestication genes have been identified in Chinese indigenous dogs, which represent an intermediate form between wolves and breed dogs. These genes show strong statistical evidence of positive selection in the southern Chinese indigenous dogs.

The top 1% of the genome bearing strong statistical evidence of positive selection in the southern Chinese indigenous dogs is related to metabolism and motility, neurological process and perception, as well as sexual reproduction. Genes involved in these categories have undergone strong selective sweeps, indicating that they played a crucial role in the domestication of dogs.

Genes related to memory and long-term potentiation (LTP) have also been identified as positively selected genes in the first stage of dog domestication. These genes, such as GRIA1 and GRIN2A, are involved in excitatory synaptic transmission and play a key role in hippocampal synaptic LTP and long-term depression.

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Genetic diversity and population structure are crucial aspects of genetics, and a recent study has shed light on these topics.

Dogs from southern East Asia, including the southern Chinese indigenous dogs, are closest to wolves in terms of genetics.

These dogs, along with several East Asian breeds, form a distinct group that is separate from other continental dog populations.

Their genetic makeup suggests a long history of separation from other dogs, with some studies indicating that they may have diverged from wolves as far back as 20,000 to 40,000 years ago.

The study found that East Asian dogs are the most basal lineages connecting to gray wolves, suggesting a common ancestor.

This is supported by phylogenetic analysis, which shows that East Asian dogs spread over both sides of the deepest node connecting all dogs.

In contrast, dogs from other continental areas coalesce into a subclade and then join with East Asian dogs, indicating a more recent common ancestry.

The study also found that dogs from Oceania, such as dingoes and New Guinea singing dogs, bear strong signals of admixture with gray wolves, likely reflecting their past history of admixture.

This admixture is thought to have occurred before they migrated to Australia and New Guinea.

The genetic data suggest that dogs from northern China show strong admixture from European dogs, indicating a recent migration event.

Gene flow from wolves to African/Middle Eastern dogs has also been detected, highlighting the complex history of dog domestication.

The study's findings have important implications for our understanding of dog evolution and the origins of different breeds.

Genes play a crucial role in shaping our traits and characteristics, and it's fascinating to explore how they influence our lives.

Domestication genes in Chinese indigenous dogs have been identified as being related to metabolism and motility, neurological process and perception, and sexual reproduction. These genes were found to be positively selected in the first stage of dog domestication.

Genes related to memory and long-term potentiation, such as GRIA1, are also of great interest. This protein plays a key role in hippocampal synaptic long-term potentiation and long-term depression.

The transformation of gray wolves to domestic dogs may have been empowered by these genes, allowing them to flourish in the human environment.

Taking care of your domestic dog requires a lot of time and effort, but with the right approach, it's definitely worth it.

Regular exercise is essential for dogs, with most breeds needing at least 30 minutes of physical activity per day.

To keep your dog's coat clean and healthy, brush them at least twice a week, with some breeds requiring daily brushing.

A balanced diet is also crucial, with most dogs requiring a mix of protein, fat, and carbohydrates to stay healthy.

On a similar theme: Dog Breeds Watch Dogs

Dogs' dewclaws are attached to their forelimbs by bone and ligament, but those on the hind legs are only attached by skin.

Most dogs aren't born with dewclaws in their hind legs, and some are without them in their forelimbs.

Dogs' dewclaws consist of the proximal phalanges and distal phalanges.

Some publications theorize that dewclaws in wolves, who usually do not have dewclaws, were a sign of hybridization with dogs.

Neutering is a common surgical procedure in dogs, especially in the US, where it's often done as early as 6-14 weeks in shelters.

In the US, neutering is the most common surgical procedure in dogs less than a year old, and it's seen as a control method for overpopulation.

However, some European countries, like Norway, have laws that prohibit neutering unless it's for the animal's health benefit.

The American Society for the Prevention of Cruelty to Animals (ASPCA) recommends neutering dogs that aren't intended for breeding to prevent unwanted litters.

Neutering can reduce problems caused by hypersexuality in male dogs, but it increases the risk of urinary incontinence in female dogs and certain types of cancer in both sexes.

In Norway, neutering is only allowed for health reasons, such as ovariohysterectomy in case of ovarian or uterine neoplasia.

Spayed females are less likely to develop cancers affecting the mammary glands, ovaries, and other reproductive organs.

Germany forbids early age neutering, but it's still allowed at the usual age.

However, neutering at a young age can increase the risk of obesity and diabetes mellitus in dogs.

The domestic dog's genome sequence has greatly improved our understanding of their origins and evolution over the past 5 years.

Scientists have cataloged over 2.5 million single nucleotide polymorphisms (SNPs) in dog breeds and wolves, allowing for unprecedented resolution of canine population genetics.

Genotyping technology has made it possible to type tens of thousands of these SNPs at a relatively low cost, around $200 per sample for a 20,000 to 60,000 marker array.

The phenotypic diversity of the world's 350 to 400 dog breeds is mirrored in their genetic diversity, with a level of diversity that's about twice that found in humans.

Most dog breeds have existed for less than two centuries, but their genetic diversity is still remarkable, with an FST average of 0.28 among dog breeds.

The recent release of the 170K Illumina HD canine SNP array and improved genome assembly will surely accelerate the pace of canine genomics, expanding our understanding of evolution in dogs and their utility as a model genetic system.

Here's an interesting read: Domestic Dog Breeds