1. Introduction

In the course of the second half of the 19th century the method of ‘inbreeding and selection’ took hold in domestic animal breeding. From 1900 onwards it was widely applied both for companion animals and in agricultural animal husbandry. Especially in the early phases of pedigree breeding (oriented to conformation) the method yielded advantages. With its use breeders were able to ‘fix’ desired traits in their breeding stock and have these transmitted reliably to subsequent generations. 

This breeding method also has drawbacks. Its systematic application concentrates not only desired genes, but also the hereditary predisposition for undesired traits. The problem is that harmful genes are being spread while successive generations display only a very limited part of these in the offspring. For every harmful trait the bulk of the unwanted genes is hidden away in carriers. We do not notice their damaging effects until later, many generations down the line, by which time the harmful genes have become so widespread that our selection is virtually powerless. On top of that, hereditary problems involving more complex transmission patterns cannot be combated with this system of individual selection at all.

In the world of pure-bred dog breeding ‘inbreeding and selection’ is still the order of the day. What it basically comes down to is this: the level of inbreeding is gradually raised (via line breeding). The purpose is to fix the superior traits of dogs in the line. Selection is in favour of the desired characteristics (the most breed-typical traits), and against undesired characteristics (such as disorders in health and well-being). There are two objectives here: ‘preservation’ and ‘improvement’.

Most breeders are convinced they are ‘preserving’ as long as they mate pure-breds only. As to ‘improving’, most breeders hold that this can be achieved by always letting the ‘best’ animals contribute as much as possible to the next generation. They assume that this approach will also check the frequent occurrence of health and well-being problems in pure-bred dogs. The reality of pure-bred dog breeding, however, yields a different picture.

by Carol Beuchat PhD

For most of history, people bred dogs to produce a particular type suitable for work, companionship, or some other purpose. Knowledge about genes and the principles of inheritance were used to improve the predictability of many traits breeders cared about- color, size, coat type, instincts, and so on.  Before the advent of kennel clubs, breeders did what worked for them and avoided breeding in ways that caused problems.

When dog breeding became a hobby and kennel clubs were formed, breeders placed value on the purebred dog and created closed registries- dogs would only be considered "pure" bred if their parents were already registered in the studbook.

Over the ensuing years, generation after generation of purebred dogs have been produced from animals already registered in the studbook. Breeders have used selective breeding to produce dogs to suit their needs, carefully choosing breeding pairs and evaluating the offspring to determine which were of high enough quality to be suitable for breeding themselves. 

At the time kennel clubs were created about the turn of the 20th century, very little was known about genetics.  Scientists were arguing about the mechanisms of evolution, and Mendel the monk was puttering in his garden doing experiments on peas.  Nobody had any notion that creating closed populations of purebred dogs might not be a good idea.  But as genetics began to develop as a discipline alongside the theory of evolution, biologists began to think about how new species evolved and the role that genetics might play.  They realized that changes in the traits of animals over time could lead to the evolution of new species, and that this was a reflection of changes in the particular mix of genes present in the animals that form a species.  If the animals in one population of a species became different enough genetically from the animals in another population, they could cease to interbreed and become separate, distinct species.  The process of evolution was really just a change in the frequencies of particular alleles that determined the traits that make the new species unique.