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Dog

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

Comparison of a wolf and a pug
Comparison of a wolf and a pug

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.

Dog anatomy lateral skeleton view (full)
Dog anatomy lateral skeleton view (full)

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.

Selected skulls
Selected skulls

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.

Walking the dog (1945527533)
Walking the dog (1945527533)

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.

Vision comparison with dogs
Vision comparison with dogs

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.

Selected skulls
Selected skulls

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."

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🖼️ Images & Media (21)
File:Dogs, jackals, wolves, and foxes (Plate I).png
Dogs, jackals, wolves, and foxes (Plate I).png
File:Dogs, jackals, wolves, and foxes (Plate IX).png
Dogs, jackals, wolves, and foxes (Plate IX).png
File:Dogs, jackals, wolves, and foxes (Plate XI).jpg
Dogs, jackals, wolves, and foxes (Plate XI).jpg
File:Dogs, jackals, wolves, and foxes (Plate VI).png
Dogs, jackals, wolves, and foxes (Plate VI).png
File:Dogs, jackals, wolves, and foxes (Plate X).png
Dogs, jackals, wolves, and foxes (Plate X).png
File:Dogs, jackals, wolves, and foxes (Plate XLI).png
Dogs, jackals, wolves, and foxes (Plate XLI).png
File:Dogs, jackals, wolves, and foxes (Plate XLIV).png
Dogs, jackals, wolves, and foxes (Plate XLIV).png
File:Dogs, jackals, wolves, and foxes (Plate XIII).png
Dogs, jackals, wolves, and foxes (Plate XIII).png
File:Dogs, jackals, wolves, and foxes (Plate XII).png
Dogs, jackals, wolves, and foxes (Plate XII).png
File:Comparison of a wolf and a pug.png
Comparison of a wolf and a pug.png
File:Dog anatomy lateral skeleton view (full).jpg
Dog anatomy lateral skeleton view (full).jpg
File:Selected skulls.jpg
Selected skulls.jpg

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