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Dogs come in all shapes and sizes. We've molded some of them to have large , sloping backs and shortened legs through selective breeding.

What is increasingly clear is that some of the extremes of physical shape, seen in many dog breeds damage their health. Despite this, many of these breeds, such as French bulldogs, . In response, the in the UK has issued guidance on ten extreme body shapes prospective dog owners should avoid.

But dogs aren't the only animals who have suffered the consequences of selective breeding.

Humans have for centuries. For animals linked to agriculture, selection has resulted in high milk-yielding dairy cows, chickens that lay eggs far more frequently than their forest-dwelling ancestors ever would have, and sheep that grow wool to excess.

The reality for many animals is that intense genetic selection for specific characteristics, whether physical or behavioral can result in serious unintended consequences.

often suffer from crippling lameness. Laying hens have a than it otherwise naturally would be—both because selective breeding has reduced their lifespan and they are often slaughtered when their high egg output slows.

Designing dogs

For our dogs and other pets, including , rabbits, small rodents and , human wants and preferences also lead to selection for aesthetic appeal. This is typically for rare, novel and baby-like features.

Sadly, the human desire to seek novelty in another sentient being is harming their health and their natural abilities, welfare and .

This is rather ironic, especially for dogs who were traditionally bred for functional reasons. These include and protecting, as well as companionship.

Dogs, cats and even rabbits have been bred to have short muzzles (brachycephalic). This affects their . Brachycephalic cats have a severe risk of health problems ranging from breathing issues to neurological disorders.

But the popularity of these animals .

Although brachycephalic breeds are not a recent creation, (pugs were from China in the 16th century, and Persians are one of the oldest known ), modern versions are much more extreme.

For many flat-faced dogs, breathing problems prevent them . They also often struggle to sleep well because of .

Other physical characteristics such as shortened legs and long backs as seen in can lead to .

Giving birth can be dangerous for many dog breeds, such as those with wide shoulders. Nearly all English bulldogs .

Redesigning

To raise awareness of the health problems many dogs experience as a result of their physique, dog welfare group the International Collaborative on Extreme Conformations in Dogs (ICECDogs) is encouraging dog lovers to choose companion dogs with more moderate, natural attributes.

ICECDogs wants people to prioritize over appearance.

This does not necessarily mean banning certain breeds, although in Germany, is seeking to develop legislation to prevent people from breeding dog in a way that results in "pain, suffering or damage".

, the breeding of Cavalier King Charles spaniels has been banned. The breed suffers from several health problems including heart conditions and , where the brain effectively protrudes from the base of the skull—an extremely painful and debilitating condition.

Aficionados of many dog breeds are now devising strategies to address their welfare. These include to identify healthy dogs to include in breeding programs to move towards a healthier population.

Awareness of genetic health conditions in other animals is growing, too. Reptile and amphibian enthusiast group the International Herpetological Society has of spider royal pythons in their shows. The genetic mutation that results in the snake's beautiful markings is also linked to a nervous system disorder that makes their heads wobble.

Move towards moderate

If you're thinking about adding a dog or cat to your family, choose one with a moderate appearance.

This means avoiding such as short legs, unusual colors (many extremes are linked with neurological issues), flattened faces, excessively muscular bodies or long backs.

How animals are represented in the media is also important. The British Veterinary Association strongly recommends that animals represented in advertising, films and TV are free from exaggerated characteristics and should exemplify .

By changing public perception about the of extreme physical features, we might start reducing the demand for pets bred for exaggerated appearance.

After all, supply will always meet demand.

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