The dog is the very first animal that a person could tame. Scientists are inclined to believe that the dog became a domestic animal in the late Paleolithic era, that is, several tens of thousands of years ago. In those days, dogs helped people hunt wild animals and guarded settlements, warning of the approach of strangers. Since then, dogs have accompanied people everywhere, helping in a variety of spheres of life. Now there are shepherds, rescue dogs, guide dogs, sniffer dogs, guard dogs and others.

The dog belongs to the dog family from the order of predatory animals. The origin of the dog as a species is not known reliably. Some scientists believe that the dog originated from the wolf, and others, that of the jackal. But most still tend to believe that the ancestor of the dog is a wolf. The appearance of dogs is very diverse. According to the official data of the International Cynological Federation, in 2013 there were 339 dog breeds in the world, and the dog of each breed looks different.

There are dogs large and small, short-haired and long-haired, with large ears and small, the coat color varies from white to black with a variety of transitional shades (beige, brown, sand, gray, ash, etc.). The smallest dogs of the Chihuahua breed – their height at the withers can be only 15 cm, and the tallest dogs are the danes, their height at the withers can be 100 cm or more.

In dogs, as in humans, the five senses are sight, smell, hearing, taste and touch. Vision in dogs is colored, but they distinguish fewer colors than humans. Dogs clearly distinguish between green, yellow, purple, blue and their shades, but the red and orange are perceived poorly. But at the same time dogs can distinguish about 40 shades of gray. Dogs are very sensitive to smells. The striking ability to distinguish and catch smells helps them to easily find a trace, determine the approximate distance to the source of the smell and extract odors from a mixture of various flavors. Due to such qualities, dogs can find people who have fallen under the rubble, and find in the airports banned items and substances.

The hearing in dogs is good, they hear twice as well as a person. The sense of touch is also well developed. Dogs are able to feel even a slight touch to their hair. They like it when they are stroked, but they do not really like it when they are hugged. The taste receptors in the language of dogs are much less than in humans. Therefore, they do not have the same taste sensations as humans. However, it is known that the sweet taste of a dog is well discerned and sweets like.