After 20 years of collecting DNA samples from dogs all over the world, geneticists at the National Human Genome Research Institute in Bethesda, Maryland finally have enough data to determine how the more than 350 modern breeds emerged around the world. The research also reveals which breeds are closely related to one another, and why some dogs are more susceptible to certain diseases.
Canines have more diversity within their species than any other land mammal. This becomes clear when you see a tiny teacup Poodle standing next to a Great Dane. From their size differences to the variations in coat color, length and texture, it’s almost hard to believe they are related, let alone from the same species!
Simply put, this diversity was man-made. Once dogs were domesticated about 15,000 to 30,000 years ago, humans began to choose the best hunters, house guards, and herding animals to breed. Some were chosen to help us survive, others to be our companions. The long-term result was the 350+ breeds we recognize today, each with their own unique traits and behaviors.
Although smaller studies have provided insight into the genetics of a small number of breeds, Elaine Ostrander and Heidi Parker’s research at NHGRI provides the only data set comprehensive enough to show how and when most came into existence.
The geneticists contacted breeders, attended dog shows and utilized previously collected data to unlock the mystery of how canine breeds developed. Over a 20 year period Ostrander and Parker obtained samples from 1346 dogs representing 161 breeds – or not quite half of all kinds of dogs. They compared the differences at 150,000 spots on each dog’s genome, to build their revolutionary “family tree”.
Almost all of the 161 breeds fell into 23 larger groupings called clades. The clades are based on genetics, but also seem to bring together dogs with similar traits like herding breeds, hunting dogs and canines bred for their strength. This shows that ancient breeders bred dogs for specific jobs. Over the past 200 years when the majority of recognized breeds appeared, modern humans subdivided those larger groups into breeds.
The data also shows how some breeds helped create others, as evidenced by a single breed sharing DNA with multiple clades. For example, the Pug was one of the first small breed dogs. Pugs were brought from China to Europe in the 1500s to breed with larger dogs and “shrink” them down. Pug DNA now represents a part of many other toy and small dog genomes.
The most important thing about these clades is that they will help veterinarians spot potential genetic problems in pets by revealing which breeds are closely related.
Peter Savolainen, an evolutionary geneticist at the Royal Institute of Technology in Solna, Sweden says the work “is a very good first step into the origins of all dog breeds, but half of all breeds are still missing.” But Ostrander and Parker assure that they are just getting started. They hope to eventually compare whole genomes—the entire 2.5 billion bases.
“We had reached a point where we could begin to do some of the things we wanted to do,” Ostrander explains. “By no means are we done.”
H/T to ScienceMag.org
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