On days when my patients go straight from Shih Tzu to Newfoundland to Whippet, I marvel that all of these dog breeds are the same species. Not only do they look different, but they also have different medical and behavioral needs. Of course, it’s not surprising, since dogs have been bred for specific purposes for thousands of years.
New research on canine ancestry reveals some interesting information about just how related different breeds may or may not be. In today’s globally connected world, it is easy to assume that all working breeds are more related to each other than they are to any of the toy breeds, for example. Geneticist Heidi Parker and her colleagues at the National Institutes of Health performed genetic analysis on more than 160 breeds and found that assumption just doesn’t meet the facts. During most of dogs’ evolution as companions, individual cultures were more isolated and yet each had the need for a variety of types of dogs. This means that dogs with similar geographic origins share more genes with each other than a similar looking breed from halfway around the world. For example, even though they look more similar, Pugs and Boston Terriers are less related than Pugs and Schnauzers.
Phenomena like this are not only found when humans purpose-breed animals. It’s similar to the emu of Australia and the ostrich of Africa. They fill a similar niche in their environment and share many physical traits though they are quite unrelated—an observation known as convergent evolution. In dogs, the giant herd guarders of Europe and the Mediterranean do not share size-associated genes with each other but each shares many genes with Sighthounds developed in the same region.
The researchers confirm previous suggestions that the modern dog originated in Central and East Asia. From there, dogs spread worldwide and were developed into the many types of dogs that were needed in an agricultural society—from protecting animals and land to hunting vermin to entertainment. The original diversification of dogs occurred thousands of years ago. We can thank the Victorian era for the “breed explosion” responsible for the development of our favorite dog breeds.
One unexpected result is that German Shepherd dog gene signatures appear in almost every dog breed founded in the Americas. The researchers suggest this may mean that an ancestor of the modern German Shepherd dog came over with explorers as early as Columbus’s era. This does not mean that a dog like the one we call a German Shepherd today was an early immigrant. Rather that the type of dog that sailed to the New World gave rise to diverse breeds on the American continents and is most directly related to those shepherds in the Old World.
Maintaining Genetic Diversity of Dog Breeds
While this new information probably won’t change anything about how you interact with your dog, it does have implications for how we maintain genetic diversity within breeds today. The research shows that even recently, breeds were often mixed together to enhance or reduce a particular trait. Today, that is against AKC guidelines for registering a purebred dog. So, to help maintain breed health, many good breeders already choose to mate their dogs with champion lines from the other side of the country or even the world. This keeps all of the breed characteristics while mixing in different genes to help reduce the risk of inherited diseases in the puppies. It also reduces the drift of traits in one population of the breed, say to longer or shorter noses.
This kind of careful breeding is important because many of the most popular dog breeds have very high risks for particular diseases. The research shows how quickly traits can change when populations are isolated. This is a concern when it impacts your dog’s health, which can happen very quickly in small isolated populations. For example, one type of heart disease is very common in Boxers and another type in Cavalier King Charles Spaniels. The lesson here is that if you are going to buy a purebred dog, do your homework. It’s important for both the health of the animal you choose and for the entire breed. If people only buy dogs from family lines free of the common diseases in that breed, the entire breed will become healthier. One great example of this is (a third type of) heart disease in Doberman Pinschers. Twenty years ago, many died young due to progressive heart disease, but today we see much less of the disease in Dobermans without loss of any of their best traits.
Hopefully this research will help inform how breeders and breed registry groups maintain genetic health in future generations of our companions. To me, it doesn’t matter what my dog is (I call him an “All-American Mutt”). It only matters that he is happy, healthy, and loves me and my human family.
Dr. Elfenbein is a veterinarian and animal behaviorist located in Atlanta. Her mission is to provide pet parents with the information they need to have happy, and healthy, and fulfilled relationships with their dogs and cats.