When we think of dogs, we often think of dog breeds, from the tiny Chihuahua to the massive Great Dane, or from the retrieving Labrador to the herding Border Collie. When we meet a cute mixed-breed dog, one of the first questions we often ask its owner is “What is that?” Playing the breed guessing game is a favorite pastime among my dog-owning friends: “I don’t know, but I like to think he’s got some heeler in him – look at that blue ticking!”
But in fact, looking around the world, breeds make up a small proportion of canine genetics. In her 2013 paper, our lab member Kathryn Lord estimated that there are between 700 million and 1 billion dogs in the world. Of those, the great majority – up to 83% – choose their mates on their own, without any interference from humans. In fact, the majority of them live on their own, making their homes near humans but not in human houses, scavenging off of our garbage.
If you trace back through the family tree of most of these dogs, you won’t find ancestors belonging to any particular breed. They are just dogs, breeding the way they have been for tens of thousands of years. Most of these dogs are much like the original dog, living in much the same environment as their ancestors thousands of years ago – in other words, scavenging on what humans leave lying around.
Breeds are, in fact, a relatively new phenomenon in the history of dogs. We don’t yet know quite how long we’ve had dogs on this planet, despite the numerous researchers who are working hard on cracking that particular puzzle, but certainly at least 10,000 years. For much of that time, dogs bred however they chose, and the resulting animal often looked like what we now call a “village dog.” These dogs were generally short haired and weighed around 30 pounds on average, though dogs living in colder climates tended to be a bit larger and have longer, thicker coats, while dogs living in warmer climates tended to be a bit smaller and have shorter, thinner coats. The most common color among these village dogs is a yellow color like a lion’s, with a white underbelly, but we see plenty of other colors as well.
Over time, dogs living near different populations of humans started adapting to that population. At first this wasn’t due to intentional human interference with dogs’ breeding choices. More likely, the first way we selected which dogs would breed was just by tolerating or even feeding those dogs who were less annoying or more helpful to us. Dogs who didn’t chase livestock would have been less likely to be driven off or killed, and dogs who drove away other predators might even get extra food tossed their way. Over time, this unintentional selection resulted in groups of dogs who were actually useful to have around, performing jobs like guarding livestock. The term “landrace” is sometimes used to describe these populations of dogs – dogs adapted for a particular part of the world and perhaps good at being helpful, but not intentionally selected by humans. These dogs still weren’t “breeds” by today’s standards. Because they were loosely bred for ability, any dog of unknown breeding could be considered a useful dog of a particular type so long as they could do the job.
Over time, some people started breeding dogs with some intention, getting dogs who were better at particular jobs, such as herding or retrieving. Dogs became more adapted to their jobs and started performing more jobs during this stage. However, breeds as we know them today didn’t appear until the Victorian era, when the “dog fancy” craze was born in England. Dog fanciers started breeding for very specific looks, like particular coat colors or ear shapes or muzzle lengths. Because their dogs were more likely to be kept in houses and under strict control than dogs in earlier ages, it became easier to control which dogs were bred. For the first time, decisions about who would be bred to whom were made for dogs on a larger scale.
As dog breeders successfully developed some dogs with particular, unusual looks, they started keeping registries – records of who was whose parent – to help them better select dogs to breed (or not breed). At some point, these registries were “closed,” meaning no new dogs were allowed in unless they could trace their ancestry entirely back to dogs who were already in the list. That was when breeds were born, along with kennel clubs to maintain the registries.
In the modern day, we understand a dog to be a member of a breed if his or her ancestry can be traced back to to dogs who were founding members of the breed – in other words, are listed in the original entries in the breed registry. If there is even one dog in a dog’s ancestry who can’t trace her ancestry back to that original breed registry, then technically, that dog isn’t purebred.
What this means for the Darwin’s Dogs project is that sometimes, when we return breed results for your mixed breed dog, we find chunks of their DNA that we can’t match to any breed. What are these chunks? Possibly they are from a breed that we don’t have in our reference panel yet. But possibly these areas of your dog’s DNA are from ancestors who trace back to village dogs – to populations of dogs who were never selected by people and never in a breed. We call these “non-breed dogs,” but really, they’re just dogs, picking their mates on their own, like most of the other animals in the world.
If you are interested in learning more about village dogs and how breeds came about, check out Coppinger and Coppinger’s 2016 book, “What is a Dog?”
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