Video: Breeding Dogs: Basic Concepts
At the beginning of our century, the most important event in biology was the emergence of a new science - genetics. However, many things and events exist outside of our understanding and do not depend on it. Thus, electricity participated in the formation of life on Earth long before man discovered the laws of the ordered motion of charged particles. It's the same with genetic laws.
Long before Gregor Mendel looked into the mysterious gene workshop, these laws helped to develop new breeds of domestic animals and varieties of cultivated plants. For the sake of fairness, it should be noted that although we, with good reason, ascribe to Mendel a "patent for the invention" of genetics, in his time there was no relatively harmonious understanding of the nature of heredity that we have now. Even the concept of "gene" was introduced half a century later by the biologist V. Johannes. From the moment when Alexander the Great first thought about the connection between the articles of his horse and his agility (this is what is considered the birth hour of zootechnics), zootechnical science has successfully developed many cultivated breeds and varieties of plants and animals.
Zootechnicians especially "tried" when breeding dog breeds. Cats, horses, cows and other domestic animals do not have the same polymorphism in external signs that dogs show.
It is this variety of external forms that is one of the main arguments in favor of the defenders of the polyphilitic theory of the origin of dogs, which implies the derivation of the family tree of dogs not from one, but from several wild ancestors - more often from a wolf and a jackal. There are other variations on this theory. Many scientists (for example, Konrad Lorenz) deduce some groups of breeds from the wolf, and others from the jackal, while some attribute to wolves and jackals "co-authorship" in the origin of dogs. There are also versions suggesting that dogs evolved from other species of wild canines. The most popular "contender" after the wolf and the jackal is the North American coyote. He freely interbreeds with a wolf (and with a dog) and is so similar to him that a layman cannot always distinguish them from each other.
Наряду с полифилитической точкой зрения существует и монофилитическая. Она подразумевает наличие единственного дикого предка собак. Эта точка зрения тоже не отличается единообразием. На роль единственного предка собаки «претендуют» четыре основных вида: волк, шакал, койот и, как ни странно, собака, то есть ее вымерший предок. Рой Робинсон отмечает, что у собак, волков, шакалов, койотов и, может быть, других псовых вероятно наличие одного общего предка. По некоторым данным, волк произошел около 500, шакал -130, а собака 50 тысяч лет назад.
As you can see, there are a lot of points of view on the origin of dogs and disputes are still ongoing. But whatever the reason for the striking ethological and morphological plasticity of domestic dogs, they represent a huge genetic diversity material for selection. However, this will be discussed below, the same plasticity has served a disservice.
On the basis of a huge genetic material, a huge number of breeds were created. It would be rather difficult to navigate in them if it were not for the multitude of classifications. The main classifications are based on origin, use, etc. Various cynological organizations around the world are establishing their own systems. However, there are drawbacks in each classification that do not allow them to be applied to all aspects of dog use. Despite this, different systems of division help to understand the variety of breeds that exist today.
One of the age-old questions of breed formation is the direction and specialization of the breed. For example, huskies, cops, hounds, wolfhounds, terriers and greyhounds are classified as hunting dogs by design. However, each of them has individual hunting methods, and hence anatomical and morphological signs. The main feature of the change in breeds in our time is the transition of many "working" breeds to the category of decorative.
By itself, such a process does not lead to fatal consequences, but there are also "pitfalls" here. As long as the breed is doing some work, there is little fear for its genetic health. But when breeding begins to be based only on exterior signs, the inexpediency of such an approach appears. In the case of the transition of a breed to a decorative group, the life of its representatives changes completely. Few dogs have enough walks two or three times a day, even two hours, and many do not get even that. Physical activity decreases, which leads to weakening of health. From generation to generation, these negative properties accumulate and weaken the gene pool.