From the tiny Chihuahua and fluffy poodle to the swift greyhound and massive Great Dane, dogs come in an array of looks and personalities. There are about 350-400 different breeds of modern dogs, and they all trace back to when dogs were first domesticated tens of thousands of years ago.
Now, a team of researchers has used DNA analysis from 161 of those breeds to determine how they evolved and which ones are most closely related to each other. They've created an elaborate dog family tree that shows those relationships. In addition to helping us understand evolution and canine history, the data could also help us understand dog diseases and why certain breeds are more susceptible than others.
Study lead author Heidi Parker, a dog geneticist with the National Institutes of Health, and her colleagues began studying dog genomes two decades ago. The research involved taking dog DNA samples, studying preexisting genetic collected data, and talking to dog owners and traveling to dog shows to compare their findings to real-live dogs.
"We wanted to understand how something that descended from the gray wolf some 15,000 to 30,000 year ago could come in so many shapes and sizes today," Parker tells MNN.
People began developing these adaptable animals for different purposes: to hunt or to herd, to guard or to be companions.
"We ask them to take on different jobs, to move around the world with us. We're constantly changing requirements," Parker says. "We kept putting these different sorts of pressures on them."
Using the DNA samples they had collected, Parker and her colleagues created this map. It, along with their study, was published in the journal Cell Reports.
Using DNA, researchers grouped 161 breeds based on genetic backstory. (Photo: H.G. Parker et. all/Cell Reports)
Nearly all the breeds fell into one of 23 groupings called clades. They're signified on the wheel by color. Most of the dogs in a clade have similar traits, such as they're all herding dogs, retrievers bred for hunting or large dogs bred for strength.
Although many of the groupings appear to make sense, others seem quizzical. In two clades that come out of the rural United Kingdom and the Mediterranean, leggy, sleek sighthounds and large, hairy working dogs that used to guard flocks were linked by DNA. Although the dogs looked nothing alike and had totally different jobs, they had some common background and ancestors. Likely some would go out hunting and others would stay home to guard the farm, but they were initially related and bred from the same dogs, Parker says.
Spotting genetic issues
Knowing which breeds are related can also help researchers and veterinarians predict diseases in specific breeds. They can look at genetic traits and determine which are mutations.
"There are floppy ears in a basset hound and floppy ears in a cocker spaniel. How closely related are they?" Parker say. "We can go back and trace mutations and look to find mutations that cause disease."
And the genetic information they find may also translate to their two-legged best friends, as humans and dogs often share the same diseases, such as diabetes, cancer and kidney disease.
"Using all this data, you can follow the migration of disease alleles and predict where they are likely to pop up next, and that's just so empowering for our field because a dog is such a great model for many human diseases," said senior co-author and NIH dog geneticist Elaine Ostrander, in a statement. "Every time there's a disease gene found in dogs, it turns out to be important in people, too."