Dogs with 'baby faces' – with round eyes and short/flat snouts – are surging in popularity. People enjoy their cute appearance, but the appearance can have severe negative effects on the dogs, causing serious health issues and suffering.

The focus of breeding dogs has been and still is primarily on modifying the appearance of dog breeds, leading to abnormal appearances. Considering the natural appearance of the wolf, Canis lupus, the ancestor of domestic dogs, very few dog breeds now share any resemblance with it.

In the animal kingdom, offspring inherit the characteristics (appearance and behaviour traits) of their parents through genetic transmission. This is a natural process that contributes to the evolution of the species. Humans can 'influence' evolution through selective breeding resulting in the variety of breeds we see today. This process involves the selection and breeding of animals with desirable characteristics, leading to offspring that inherit the same traits. But selective breeding, when taken to the extreme, can lead to the development of genetic disorders. And indeed, numerous dog breeds today suffer from severe health issues caused by extreme physical features.

Genetic disorders are health problems caused by 'flaws' in an individual’s genome. While this is a natural phenomenon in wild animals, artificial selection increases both the number of genetic 'flaws' and their chance of being expressed.

When it comes to dogs and other pets, there is a limited number of individuals that possess certain traits that are desired for breeding. To bring these traits to the next generation it is common to breed closely related animals, or even worse, animals that are already affected by genetic disorders. Selective breeding that uses animals with known disorders and that disregards health implications is commonly known as 'breeding of defects'.

Dogs have evolved from domesticating wolves. Although still unclear, it is generally believed that early humans were accompanied by one Palaeolithic dog 'breed'. Since the selective breeding of dogs began, the appearance of dog breeds has been altered, and entirely new breeds created. By comparing historic and contemporary photographs of dogs, the selection for extreme features becomes apparent. For instance, Pugs have shorter noses, the Dachshund has a longer body, the Saint Bernard has increased in size, and the German Shepherd now has a sloped back.

For centuries, different types of dogs have been bred with different purposes: for work, sport or just for companionship. During the 1800s, in Britain people began to breed in a more selective manner focusing on shape, size, fur and colour, and the actual term 'breed' first appeared. 

The development of dog shows further drove the importance of breeds and their appearance. The first pedigree dog exhibitions took place in the mid-19th century. As soon as people started exhibiting and competing with their dogs, they wanted to diversify and improve the appearance of breeds. In the early days of these exhibitions there were no set standards – the dogs that were 'liked' best by the judges were awarded prizes. The decisions were often controversial. Breed standards have evolved over the years.

Nowadays, breed characteristics are prescribed down to the smallest detail, outlining what the pure-breed characteristics should be.

There are 360 dog breeds currently recognised by the FCI (Fédération Cynologique Internationale), the umbrella organisation overseeing canine breeding worldwide. Overall, 757 genetic disorders have been described in dogs¹. A study of the 50 most popular dog breeds in the UK, for example, found that each of the studied breeds had at least one genetic disorder, with Labrador Retrievers reaching up to 50 inherited disorders².

Selective breeding and the resulting issues are a great concern. The health of dogs should be the priority for breeding, not the appearance of the individual animal.