Melvin is an avid reader and a retired chemist after working for a major pharmaceutical company for 32 years.
Selective Breeding in Dogs
Today there is a myriad of animals in the world due to natural selection by the process of evolution. Natural selection ensures the survival of a species by selectively transferring the best genetic information from one generation to the next to improve that species' chances of survival.
However, there is another way specific genetic characteristics of animals such as size, strength, fur color, etc., can be transferred from one generation to the next generation. This is called selective breeding or artificial breeding. It is the same process as natural selection but involves the intervention of man, and the results of the process can be observed in a much shorter timeframe as compared to natural selection.
The timeframe of natural selection can be short or very long, depending on the species under observation. Also, natural selection is a result of a chance encounter with another animal of that species or an environmental pressure such as regional climate, food availability, predators, or population size. This means it may take thousands of years to observe a change in a species in natural selection.
For some animals and some plants (crops), selective breeding has been going on for thousands of years. Corn was once wild grass seeds until it was developed by selective breeding into what it is today; yellow, large, and edible kernels.
Consequently, dogs have become the most popular animals for this type of activity, and over the last 200 years, selective breeding has produced more than 400 breeds of dogs, specifically as show dogs in dog shows and as companions in many homes around the world. But the downside to all this selective breeding of dogs is that it has taken a terrible toll on man's best friend in terms of their health. Today, many of these dogs have a lot of health problems. In some cases, behavior problems are a result of selective breeding.
A Brief Lesson About the Origin of Dogs
Before I proceed further on the details of selective breeding with dogs, let me start off with a brief introduction to the classification of dogs in the animal kingdom. I hope you know your Latin.
In the animal kingdom, dogs are located at the following address in the tree of life. They are in the Chordata phylum of the Animalia kingdom since they have a backbone and are in the class called Mammalia because they are endothermic, which means they produce heat internally and have three bones in the middle ear, have hair, and have mammalian glands to produce milk for their young.
Dogs are meat-eaters, so they are in the subgroup or order of mammals called Carnivora. They are in the family of carnivorous mammals called Canidae since they are descendants of wolves. This family also includes foxes, jackals, and dingos. Dogs are in the Canis genus and are specifically classified in the subgroup of the Canis genus called Canis lupus or C. lupus, which designates the grey wolf as the main ancestor of dogs. Dogs are in the subspecies of Canis lupus called Canis lupus familiaria.
History of Dog Breeding by Human Intervention
About 14,000 years ago, the evolutionary path of some wolves, Canis Lupus, was altered when some of them wandered into prehistoric camps in search of scraps. According to Dr. Joshua Akey, assistant professor of genomics at the University of Washington, it was this pivotal point in time when some wolves started down the path of domestication to become the dogs we see today. So for the next few thousand years, dogs basically remained wolf-like in appearance but their behavior slowly changed from a wild predator-type personality to a more friendly, domesticated one. They became more approachable to humans as a result of this change in behavior.
Even though selective breeding has been going on for thousands of years with dogs, most of the 400 breeds we see today were created by selective breeding in the last 200 to 300 years by farmers, hunters, and royal families. It was this observation made by Charles Darwin on the multitude of dog breeds that lead him to develop the Theory of Evolution. He knew at the time that all these breeds of dogs were due to different genetic information being transferred from one generation to the next depending on the parents of the dogs. But he could not explain how this was happening at the time.
Scientists today know that there are approximately 155 regions in the genome, total hereditary information, of dogs totally responsible for all the different breeds we see today. Each region contains about 11 genes that cause the changes such as fur color, dog size, leg length, tail length, dog size, etc. Dog breeders use these characteristics of dogs to produce larger dogs, smaller dogs, dogs with short legs, dogs with short tails; the list goes on. But all this selective breeding with dogs has come with a price.
Many of these relatively new breeds of dogs are suffering from a myriad of health problems and a lot of it has to do with inbreeding through selective breeding. The majority of these breeds have more than one health problem and the interesting thing about all of this is that the more wolf-like a dog is in appearance, the fewer health problems it has when compared to the least wolf-like dogs such as pugs and toy dogs.
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Today, a lot of these traits are fatal for some domesticated dogs and these traits would put a lot of dogs at a disadvantage if they were released into the wild. These dogs simply would not survive long out there if they were to encounter one of their ancestral wolf cousins or a dog that has become feral.
Common Dog Health Problems of Popular Breeds
Selective breeding has created a number of health problems, affecting both body and behavior of the dogs. For example, the flattened face of a pug or bulldog is one of many traits brought on by selective breeding, but all these dogs have breathing problems since their nasal cavity is much shorter than that of their ancestors and other dogs.
Many skin problems of dogs are caused by selective breeding. For instance, the Chinese Shar-Pei has an unusual trait of very loose skin, but they are especially prone to skin infections. The folds in their skin are ideal places for staphylococcus bacteria to breed. Some dogs such as the Dalmatian, Boston Terrier, and many other terriers suffer from a skin condition called atopic dermatitis, which is an inflammation of the skin accompanied by itching.
Diabetes, a disease we are all very familiar with and is prevalent in humans, is also a serious health problem among such dogs as Samoyeds and Australian Terriers. They face the same consequences we do, such as leg and foot amputations, blindness, and kidney damage if their blood sugar levels are not well managed.
Doberman Pinschers and Bassett Hounds are two breeds of dogs that suffer from blood disorders that cause clotting problems. They bleed profusely and bruise very easily after injuries. Dobermans also suffer from sudden death from cardiovascular diseases. Also, many dogs suffer from high blood pressure. These dogs are generally small dogs such as Poodles and Cocker Spaniels.
Cancer, Leukemia, and Brain Tumors
Big dogs such as the Great Dane, Rottweiler, Labrador, and Irish Wolfhound also have their own set of health problems, basically because of their size. These dogs have a higher risk of cancer than smaller breeds. The incidence of bone cancer is prevalent in large dogs because their bones are under a lot of stress from the extra weight on them. Also, the incidence of leukemia and brain tumors is high in this group of dogs. The poor Scottish Terrier has an 18 times higher chance of getting bladder cancer than other dogs.
Despite the fact that dogs are able to hear better than us, many of them suffer from hereditary hearing loss. English Settlers, Dalmatians, and Australian Cattle Dogs are the main carriers of this genetic defect magnified by selective breeding. Another sense affected by breeding is vision. Siberian Huskies, Samoyeds, and Bichon Frise are dogs that suffer from a hereditary form of cataracts as they get older.
Finally, many small dogs and dogs with short legs suffer from orthopedic problems, problems that are bone-related. Dogs such as the Saint Bernard and German Shepherd are heavy and large dogs. Their weight puts a lot of pressure on the bones of the hip. Large dogs with long necks and large heads often have problems with their spinal cord. The weight of their head places a lot of pressure on their vertebra in the neck, causing them to pinch or compress the spinal cord. These dogs have the tendency to wobble and sometimes fall while walking. Small dogs such as the Basset Hound and Dachshund suffer from bowed legs because of their short legs. Toy dogs have a higher incidence of kneecap dislocations.
Even though I only mentioned a few of these health problems here, there are many more illnesses and other health problems that other breeds of dogs have, but it would have been a lengthy article for me to elaborate on all of them. In addition, a recent study published in the Journal of Neuroscience entitled, "Significant neuroanatomical variation among domestic dog breeds," found evidence that selective breeding over thousands of years has changed their brain as well, thus affecting their behavior.
Selective Breeding Comes With a Heavy Price
Selective breeding has created hundreds of breeds of dogs that many dog owners proudly present annually at the New York Westminister Dog Show and other dog shows around the world. The show is something to watch and enjoy, and it is the only chance where you can see a wide variety of dogs under one roof.
Unfortunately, as I mentioned earlier, these dogs are paying a heavy price to become the top dog at these shows. When we watch these shows, we can clearly see that many of these dogs would not be here if it was not for selective breeding. Many of them simply would not survive in the wild with these artificially created traits.
© 2012 Melvin Porter
L. Jay on April 30, 2020:
Some breeds look similiar to wolves in appearance. Are they healthier?
Melvin Porter (author) from New Jersey, USA on May 29, 2012:
DrMark1961, thanks for the comment. Mixed breeds generally do not have as many of these health problems I mentioned in the article. Most of the problems occurred because of inbreeding to produce purebred dogs with the desire features breeders are trying to archive. Mixed bred dogs are very close to what would have happened naturally with dogs in the wild. This is what natural selection is about, animals meeting by chance to perpetuate their species.
Dr Mark from The Atlantic Rain Forest, Brazil on May 29, 2012:
Thanks for the research. Selective breeding has its good and bad points. I have a mixed breed dog at the moment because she is so much healthier than the pure breds but I definitely would not want a wolf, no matter how healthy she was.
By the way, have you looked at wild corn? It is nothing like the fine plant we have produced with thousands of years of selective breeding
Melvin Porter (author) from New Jersey, USA on May 29, 2012:
Nettlemere, you are right. Selective breeding is not always a bad thing. In some cases it has improved the health of some breeds of dogs but the vast majority of them are suffering from the consequences of selective breeding. Thanks for your comment.
Nettlemere from Burnley, Lancashire, UK on May 29, 2012:
Very well researched and evidenced article and certainly some of the breeds you have mentioned are renowned for health problems and shorter lifespans.. In a few cases though I would argue that selective breeding has improved the health of dogs over the wolf. Wolf lifespan in captivity is reported to be around 15 years (less in the wild). A few of the smaller breeds of dog like the Parson Jack Russell quite regularly exceed that lifespan as does the Border Collie which is an indicator that they are fairly sound genetically.
Melvin Porter (author) from New Jersey, USA on May 29, 2012:
mwilliams66, thanks for your comment. Selective breeding has its advantages and disadvantages depending on what are the end results of the breeding. Unfortunately, for dogs and cats, selective breeding has created a host of health problems for them.
mwilliams66 from Left Coast, USA on May 29, 2012:
Melpor, you have presented a very comprehensive and truly outstanding argument against the practices of selective breeding. I am in absolute agreement with you.