Famous for their stocky charm, wrinkly cuteness, and playful personalities, English bulldogs have become one of the most popular dog breeds in the US over recent decades. However, most of these lovable traits are far from natural, and have been bred into these good-natured canines by humans. As a side effect, bulldogs have also become riddled with health problems, and sadly for them, new research suggests that continual inbreeding has left their genetic diversity so narrow that it may no longer be possible to correct these abnormalities using their existing gene pool.

Over the years, English bulldogs have been designed to display a number of phenotypes, including brachycephaly, which refers to a shortened skull, and a skeletal disorder called chondrodysplasia that accounts for their bulky build. As a result, they often suffer from major breathing and joint problems, leading to particular difficulties when mating and giving birth.

As if that weren’t enough, the breed’s wrinkly skin creates folds that are highly prone to infection, while they have also developed a weak immune system.

Correcting these problems requires that the English bulldog genome contain enough diversity for more desirable genes to be bred back into the population. However, writing in the journal Canine Genetics and Epidemiology, researchers claim that after examining the genetic diversity of 102 bulldogs, the possibility of achieving this seems unlikely. As such, it may be necessary to start cross-breeding English bulldogs with other breeds in order to restore their health.

When looking at the number of alleles – or gene variants – at 33 different positions on 25 chromosomes, the study authors found that huge regions of the English bulldog genome have become virtually identical in all individuals. For instance, only four paternal haplotypes – or group of genes passed down the male line – were identified at certain positions, one of which was present in 93 percent of dogs in the sample.

“The extensive loss of genetic diversity is most likely the result of a small founder population and artificial genetic bottlenecks occurring” as a result of continued inbreeding, explain the authors. This extreme heterogeneity, they claim, “will make it very difficult to improve breed health from within the existing gene pool.”

In light of this finding, all dog lovers should bear in mind that, though some breeds may be attractive, they often suffer greatly for their cuteness, and continuing to breed certain characteristics into them is actually rather cruel. Accordingly, study co-author Niels Pedersen explained in a statement that “the English bulldog has reached the point where popularity can no longer excuse the health problems that the average bulldog endures in its often brief lifetime. More people seemed to be enamoured with its appearance than concerned about its health.”

^{Image: brachycephaly, which refers to a shortening of the skull, can lead to serial breathing difficulties. Ammit Jack/Shutterstock}