Dogs: Origins, Evolution, and Breed Concerns of Man’s Best Friend

The English bulldog looks quite different from
its wolf ancestors.

 

“ A dog is the only thing on earth that loves you more than he loves himself.” – Josh Billings

For thousands of years, dogs have faithfully served by man’s side. Along the way, different breeds have emerged with distinctive personalities and skills. German shorthaired pointers are great hunting dogs while Doberman pinschers are loyal guardians. The little Maltese is a popular lap dog, and the Russell terrier is known for its spunky energy. These diverse dogs all share an ancestry and belong to the same species, but human intervention produced both massive working dogs as well as the tiny balls of fluff that inhabit couch cushions today.

Origin of Dogs:

The exact origin of all canine companions remains a mystery. Early evidence suggests that dogs were first domesticated in Europe, but a more recent study claims that man’s best friend first emerged in Asia (see ASO Trending News here). Some scientists, like geneticist Greger Larson, believe that both are true and dogs were domesticated independently in both Eastern Eurasia and Western Eurasia.

Scientists are also working to identify the direct ancestor of the modern dog. A 2014 study compared the DNA of dogs with various species of gray wolf across the world. The surprising results indicated that modern dogs are not descended from gray wolves; rather, both species are descended from a now-extinct ancestral species of wolf (read more here).

Gray wolves are the closest living relative
of domestic dogs.

In the Wild:

Since the split of domestic dogs from their wolf ancestors, humans have taken charge of the evolution of dogs. In nature, however, natural selection is hugely responsible for the changing of a species over time. Here’s how it works:

  1. First, there must be variation in traits. Individuals in a species must have some characteristic that is different than in other individuals. For example, some wolves might have greater muscle mass than others.
  2. This trait must be hereditary, usually meaning that a parent could pass the genes responsible for the trait down to a child. In this example, muscular parents would produce muscular offspring.
  3. Finally, for natural selection to act upon the characteristic, the trait must affect reproduction. For example, more muscular wolves could catch more prey, live longer, and produce larger numbers of healthy babies to carry on the trait for increased muscularity.

In the wild, this process is usually very slow. In the example above, “muscular” individuals might only have a small percentage of increased muscle mass. It could take many years for this small trait to have an impact on the whole population.

Under human influence, however, this process can be largely bypassed. When humans domesticate animals, they provide food, water, and safety. In this way, environmental pressures are removed from the species.

Through a process called selective breeding, or artificial selection, humans can decide which traits the offspring will most likely possess. In the case of canines, this process of artificial selection has created incredibly diverse lines of domestic dogs, which are called breeds.  

Artificial selection has allowed humans to breed great hunting partners, service dogs, drug sniffers, guardians, and affectionate companions. By selecting for certain characteristics like size, temperament, and color, humans have refined dog breeds to certain standards and qualifications. For these reasons, artificial selection can be incredibly useful. Unfortunately, it can also result in a number of complications that wouldn’t otherwise be present in a system governed by natural selection.

The Problems with Artificial Selection:

A modern bulldog.

Image from the study by N. Pederson et al.. Portrays a bulldog on an advertising label from 1935.Over time, the general physique of the English bulldog has gravitated towards certain traits.

Since this 1935 advertisement, the English bulldog has been bred for a shorter snout and stockier, shorter body.

Several breeds, such as the English bulldog, have been bred to unhealthy extremes. Although treasured by the Bulldog Nation, these dogs can be very sick. Once a healthy breed, the English bulldog now faces a myriad of health problems and a shortened lifespan. Relatively healthy bulldogs may live about 8.3 years, but sickly individuals will live only 5-6 years.

 

One of the major health problems that bulldogs face, called brachycephalic syndrome, is due to the breed’s distinctive, flat head shape.These dogs often have small, flattened breathing passages which result in significant respiratory problems. In fact, bulldogs may commonly sleep on their backs in order to breathe easier. This behavior is often seen as “cute,” but it can be a sign of a serious health problem.

Additionally, bulldogs can suffer severe complications during reproduction due to their distinct skeletal shape. The stocky body of the bulldog often makes mating difficult or impossible, and breeders must carefully monitor the process. Instead, many breeders will decide to use artificial insemination to impregnate the female. Once the pregnancy has come to term, human intervention is required again. Up to 86% of bulldog births require a c-section because the puppies’ heads can be unnaturally large for the mother’s pelvis. Once grown, the bulldog puppies have a high risk of skeletal disorders, skin problems, and a host of other health issues that would almost surely result in the extinction of bulldogs if humans did not perpetuate the breed.

A 2016 genetic study of the English bulldog revealed some disturbing truths about the health of the bulldog gene pool. In order for any species to be healthy, there should be a diverse breeding population. If individuals are too genetically similar, their offspring could have compounded health problems from both parents. This is why humans shouldn’t produce offspring with close relatives. In some dog breeds like the English bulldog, however, inbreeding has reduced the health of many lineages. The health problems already present in the anatomical structure of the bulldog have been complicated by unsafe breeding practices designed to keep “pure” lines with certain desirable characteristics.

Both the bulldog and German shepherd dog face health problems due to artificial selection for certain traits.

Human preference has resulted in a number of breeds with significant health problems. The pug, Boston terrier, and Shih Tzu also suffer from brachycephalic syndrome due to their flat faces and small skulls. “Wrinkly” dogs like the Chinese Shar-Pei often face dermatological infection when moisture, bacteria, and yeast build up in deep skin folds. Additionally, the dachshund is subject to intervertebral disc disease in its elongated back. These are just some of the more prominent examples, however, and many other breeds suffer from specific, acute health problems.

The results of these irresponsible breeding methods have been severely damaging to the health of many breeds. As long as certain characteristics remain popular, however, the supply will meet the demand.

Future Outlook:

Humans have engineered many healthy breeds using artificial selection, but irresponsible breeding has resulted in breeds with severe health problems. In order to fix these problems, significant action is required in one form or another.

Unfortunately, “tradition” is likely working against healthy dog breeding. Strict AKC standards, societal preferences, and even mascots like Uga encourage unhealthy dog breeds. Fortunately,  a shift in public attitude away from harmful traits and toward healthier breed standards or crossbreeds could help remedy the problem. Mixed breeds often have a lower incidence of harmful genetic disorders, so adopting a mutt could mean a healthier pet. (See Athens Humane Society for adoptable pups!)

Simply crossbreeding a pug and a beagle produces a much healthier snout length and reduces risk of brachycephalic syndrome. Images from the Royal Veterinary Conference Report 2013.

In a 2013 poll at the Royal Veterinary College at the University of London, a shocking fifth of veterinarians said that they would support a ban of “unhealthy” breeds. Up to a third of vets agreed that a ban should be instated within a decade if the health of certain breeds did not significantly improve. Although any type of ban seems extreme, it would put a halt to the breeding of unhealthy animals and encourage the public to think about their choice in pets.

Over thousands of years, the domestic dog has served mankind faithfully. Whether they are a hard-worker or an enthusiastic cuddler, dogs have a reputation for completely loving their role as man’s best friend. Now it’s time for some careful reevaluation of certain breeding practices and societal preferences to give canine companions the long, healthy, and happy lives that they deserve.

 

About the author:

Amanda Piehler is an undergraduate at UGA double-majoring in Biology and Mass Media Arts. When she’s not adventuring in academia, you can find her dancing, running, cooking, SCUBA diving, or hiding out in a local theatre. Connect with her on Facebook or email her at apiehler@uga.edu! More from Amanda Piehler.