Dog

Dogs come from wolves.

They were the first animals to live with people.

Dogs can be many shapes and sizes. Some are very big. Some are very small.

They all have about 42 teeth.

A dog's nose is amazing. They can smell much better than we can. They can also hear very well.

Their eyes see colors like blue and yellow.

Dogs do many jobs. They can help police. They can help people who are sick. They can also herd sheep.

Dogs use their bodies to talk. They use their faces and tails. They are our best friends.

Dogs are domesticated animals. They come from wolves.

Long ago, hunter-gatherers began living with wolves. This happened over 14,000 years ago. Some studies say it may have started even earlier. Dogs were the first species to live with humans.

Dogs come in many shapes and sizes. A Great Dane is very big. A Chihuahua is very small.

Most dogs have about 42 teeth. They use special teeth called carnassial teeth to cut meat. Their bones help them run fast. Most dogs have the same number of bones. This is true except for their tails.

Dogs have great senses. Their sense of smell is very strong. They have many more smell receptors than humans do.

Their hearing is also very good. Their eyes see colors like blue and yellow. They do not see red or green well. Dogs can even feel the Earth's magnetic field. This helps them know which way is north.

Dogs do many jobs for people. They can herd sheep or hunt. They can help police or the military. Some dogs help people who are sick. They are often called "man's best friend."

Dogs are amazing animals that live alongside people all over the world. They are domesticated descendants of wolves.

This means they share a common ancestor with the gray wolf. Dogs were the very first species to be domesticated by humans. This began over 14,000 years ago during the Late Pleistocene era. Some genetic studies suggest this process may have even started over 25,000 years ago. Because they have lived with us for so long, dogs can thrive on diets rich in starch. This is something other members of the dog family cannot do easily.

Dogs have many different bodies because humans bred them for specific traits. There are around 450 official dog breeds in the world.

They vary greatly in their shape, size, and color. A Great Dane is one of the largest breeds. A tiny Chihuahua is one of the smallest. Most healthy dogs have the same number of bones, though their tails vary. Their jaws hold about 42 teeth. They use special teeth called carnassial teeth to cut meat into small pieces. Their skeletons are built well for running and moving quickly.

A dog's senses are very different from our own. Their sense of smell is much stronger than ours.

Some breeds, like the bloodhound, have nearly 300 million smell receptors. Their brains even have a large olfactory cortex to process these scents. Dogs also have a great sense of hearing. Their vision is dichromatic, which means they see the world in blues, yellows, and grays. They have a hard time seeing red or green. Some studies even suggest dogs can feel the Earth's magnetic field.

Humans have worked with dogs for thousands of years. Hunter-gatherers were the ones who first domesticated them.

One of the earliest known domesticated dogs was found in Bonn-Oberkassel, Germany. This dog lived between 14,000 and 15,000 years ago. It was found buried alongside a man and a woman. In 1758, a scientist named Carl Linnaeus gave dogs their scientific name. He called them *Canis familiaris*. He thought they were a separate species because of their upturning tails.

Today, dogs play many important roles in our lives. They can be hunters or help herd farm animals. Some dogs work with the police or the military. Other dogs act as therapy animals or help people with disabilities.

They use eye contact, facial expressions, and body posture to talk to us. They even use scents to communicate. Because they are so helpful and loyal, many people call them "man's best friend." There are between 700 million and 1 billion dogs living on Earth today.

The domestic dog, known scientifically as *Canis familiaris*, is a domesticated descendant of wolves.

Dogs are members of the family Canidae and are classified as a subspecies of *Canis lupus*. This classification means they are closely related to gray wolves and dingoes. Dogs are unique because they have adapted to live alongside humans for thousands of years. This long association has even allowed them to thrive on starch-rich diets. Such diets would be inadequate for other members of the canid family. Today, dogs are found all over the world and serve many different roles.

The physical mechanism of a dog's body is highly specialized for movement. Their skeletons are well adapted for running. The vertebrae on the neck and back have extensions for muscles called epaxial and hypaxial muscles. These muscles connect to the spine to provide strength. Their long ribs create necessary room for the heart and lungs. Interestingly, the shoulders are not attached directly to the skeleton. This lack of attachment allows for greater flexibility during movement. While breeds vary, most healthy dogs possess the same number of bones, excluding the tail.

Dog breeds show incredible diversity in morphology, which refers to their physical shape and structure. There are approximately 450 official breeds, which is more than any other mammal.

Most of this diversity appeared during the Victorian era through artificial selection. This is when humans took control of natural selection to breed for specific traits. Dogs can be categorized by their skull shapes. Some have an elongated shape called dolichocephalic, like sighthounds. Others have an intermediate shape called mesocephalic. Some have a very short and broad skull known as brachycephalic, such as the mastiff. These shapes, along with variations in size and fur, allow dogs to fulfill specific roles.

The history of dog domestication is a subject of intense scientific study. Genetic studies suggest the domestication process may have begun over 25,000 years ago. One theory posits that dogs were domesticated in Siberia 23,000 years ago. They may have then dispersed into the Americas and across Eurasia. The earliest conclusively identified domesticated dog was found in Bonn-Oberkassel, Germany. This dog lived between 14,000 and 15,000 years ago. It was buried alongside a man and a woman. Evidence shows this dog survived canine distemper as a puppy. This suggests early humans provided intensive care even before the dog was useful.

A dog's sensory capabilities are vastly different from those of humans. Their most prominent sense is smell. The dog brain is dominated by a large olfactory cortex to process scents. Some breeds, like the bloodhound, possess nearly 300 million smell-sensitive receptors. This is about forty times more than humans possess. Their vision is dichromatic, meaning they see the world in blues, yellows, and grays. They have difficulty distinguishing between red and green. While their visual acuity is up to eight times less effective than humans, their hearing is superior. Some studies even suggest dogs can sense variations in Earth's magnetic field.

The global dog population is estimated to be between 700 million and 1 billion. The distribution of these dogs is quite uneven across the globe. Approximately 20% of the world's dogs live in developed countries. Around 75% of dogs are estimated to live in developing countries. Many of these are feral or street dogs. In the United States, dogs are the most popular pet. They are present in 34% to 40% of all households. This massive population highlights the deep connection between dogs and human society.

Dogs communicate through a complex system of signals. They use eye gaze, facial expressions, and vocalizations to convey meaning. They also use body posture, including the movement of limbs, to communicate. Chemical communication is also vital, involving scents, pheromones, and taste. Dogs often mark their territories by urinating on them. This behavior is more likely when they enter a new environment. Over millennia, dogs have uniquely adapted to understand human behavior. This ability to communicate with people has earned them the nickname "man's best friend."