A bulldog named "Roscoe" who is probably lovely. Image: Flickr/Jim Pennucci
When it comes to dogs, few sights are sadder than a tired bulldog, gasping for precious oxygen. You've probably seen one—its watery eyes drooping under folds of skin, while stubby little legs buckle under the weight of its body.Bulldogs are abominations of nature, and it's definitely our fault.A new study shows just how deeply we've warped this canine's genetic makeup. Purebred English bulldogs will never be healthy, thanks to generations of calculated inbreeding in pursuit of "ideal" characteristics. The paper's findings, which were published today in Canine Genetics and Epidemiology, mark the first time the breed's diversity has ever been investigated on a DNA level, rather than by pedigree.
"Just as it took decades, and maybe centuries, to breed the bulldog to its present form, it may take a very long time to reverse what has been done. English bulldogs have lost so much genetic diversity, and the bad traits have become so universal to the breed, that either such positive traits no longer exist, or that they exist in a very small proportion," lead author Niels Pedersen, a professor at the UC Davis School of Veterinary Medicine's Center for Companion Animal Health, told me.
A team of veterinary researchers analyzed the DNA of 102 registered, or "show quality," English bulldogs, both from the US and other countries. After their genes were sequenced, they were compared to those of puppy mill dogs, based on the notion that commercial bulldog breeders were responsible for propagating health issues common to the breed.Among both groups, it was clear that large portions of the English bulldog's genome have been affected by centuries of selective breeding. Researchers identified a significant loss of genetic diversity in the region responsible for normal immune responses. And in regard to problematic traits like skin wrinkling and hip dysplasia, the lack of diversity left in bulldog DNA leaves little hope for "weeding out" issues from within the existing gene pool.Additionally, the study revealed that breathing problems associated with brachycephaly—the flat, wide skull emblematic of most bulldogs—are a product of complex changes to the dog's head structure, and can't be fixed simply by "lengthening" the face.
A 2015 survey conducted by The Kennel Club discovered inbreeding among pedigree bulldogs skyrocketed during the 1980s and 1990s. This genetic bottleneck, or loss of diversity, is thought to have occurred when several popular sire dogs were repeatedly used to build up the population.In a separate study, published in the Public Library of Science Genetics, Swedish researchers also found genes that predispose bulldogs to a certain type of brain cancer called canine glioma, which is cancer of the brain's glial cells. According to their results, the repeated selection of brachycephalic breed traits (basically, a smooshed face with an underbite), which appear in the same region of the genome linked to glioma, could be to blame for its diffusion.English bulldogs originated somewhere in the British Isles, and were used for the now-outlawed sport of bull baiting. Technically "working" dogs, the breed soon outgrew its usefulness as humans selected for debilitating traits, such as stockiness, wide jaws, and massive heads. Today, more than 80 percent of bulldog litters are delivered by Caesarean section.Most English bulldog owners can expect their animals to die of cancer or cardiac arrest, if not old age. A small cohort of breeders is attempting to resurrect the original bulldog, which they call the "Olde English Bulldogge," though researchers warn that rapidly introducing new diversity into the gene pool could be harmful."I think that the attempt to create a dog with many of the desired attributes and physical features of the bulldog, but free of the serious health problems, is laudable. They obviously saw the writing on the wall many years ago, and had the foresight to break away from the established English bulldog breed and make the necessary changes," Pedersen added.When I asked Pedersen whether a hybrid would be a good compromise for people who want bulldogs, but not the health issues, his reply was hopeful."If the cross was to a non-brachycephalic, non-chondrodystrophic dog with a normal tail and unwrinkled skin, I would definitely say that the cross would be healthier than its bulldog parent."