Dog Breed Evolution
The dog, more than any other mammal, it has evolved to a multitude of breeds. It is estimated that there are more than 300 breeds worldwide, of which, 160 represent Scandinavian countries. Before the classification ofoccurred throughout the world, a natural evolution took place which in turn created types of which adapted perfectly to the environment and conditions in which they lived. It is believed that at the beginning the dog was a relatively slow animal that would not only trust in his sharp sense of smell and hearing, but also in its perseverance and physical resistance to follow traces of his bait and end up catching it. However, in the prairies and deserts, its speed was the only way of escape from wild hunts when it was seen hunted by its enemies. In such cases, limbs that had qualities far different from the constant "trotter". A new dog was created, a fast hunter, of long legs and arms, short body, able to reach high speeds that would depend more on its sight than its sense of smell when it would chase its bait in an open field. This breed became the currently known "sight hounds", which are very fast but that have a limited resistance. When the borzoi was used to catch rabbits, and sometimes wolves and foxes, in Russia, it was well known that the rabbit would end up escaping if the dog didn't catch it in the first 60 seconds. This proves that the dog could not maintain its speed for a long time.
Besides these breeds whose evolution has been obtained by a natural method, some breeds have evolved as a result of mutations, in other words, from complete divergences which man has controlled through breed selection. Such mutations are not rare among animals, however since these animals develop in disadvantaged conditions for some reason or another, they usually succumb to survival of the fittest and disappear. For instance, a mutation that is the cause of a lack of pigmentation in a newborn coati makes it white instead of the normal color that protects it. Therefore it becomes an easy target for its natural enemies, and rarely does it survive.
Mutations in domestic animals that man considers useful have always been adopted by him as part of a well planned out breeding in order to establish the peculiarity that it involves. These peculiarities have been developed gradually until attaining the characteristics of the breed. The dachshund or the badger dog is an example of a breed that had its origin as a mutation. In this case, the mutation affected its legs, which would stay in short at the beginning of its development, which in turn developed to the short legs that is now the main physical feature of the breed. This phenomenon is scientifically known as condrodistrofia. The bulldog breeds also belong to the group that has inherited the condrodistrofia characteristics.
Cross breeding the "main breeds" with one another, has produced new breeds that constitute a great variety of different types and sizes of, from the smallest, which weighs only a few kilos, to those that weigh 90 kilos.