The evolution of dog breeds mapped
When people migrate, Canis familiaris travels with them. Piecing together the details of those migrations has proved difficult because the clues are scattered across the genomes of hundreds of dog breeds. However, in a study published in Cell Reports, researchers have used gene sequences from 161 modern breeds to assemble an evolutionary tree of dogs. The map of dog breeds, which is the largest to date, unearths new evidence that dogs traveled with humans across the Bering land bridge, and will likely help researchers identify disease-causing genes in both dogs and humans.
|The map of dog breeds, which is the largest to date, will likely help researchers identify disease-causing |
genes in both dogs and humans [Credit: NIH Dog Genome Project]
Most popular breeds in America are of European descent, but in the study, researchers found evidence that some breeds from Central and South America -- such as the Peruvian Hairless Dog and the Xoloitzcuintle -- are likely descended from the "New World Dog," an ancient canine sub-species that migrated across the Bering Strait with the ancestors of Native Americans. Scientists have previously reported archaeological evidence that the New World Dog existed, but this study marks the first living evidence of them in modern breeds.
"What we noticed is that there are groups of American dogs that separated somewhat from the European breeds," says study co-author Heidi Parker of the NIH. "We've been looking for some kind of signature of the New World Dog, and these dogs have New World Dogs hidden in their genome." It's unclear precisely which genes in modern hairless dogs are from Europe and which are from their New World ancestors, but the researchers hope to explore that in future studies.
|Cladogram of 161 Domestic Dog Breeds [Credit: NIH Dog Genome Project]|
Herding breeds, though largely European in origin, proved to be surprisingly diverse. "When we were looking at herding breeds, we saw much more diversity, where there was a particular group of herding breeds that seemed to come out of the United Kingdom, a particular group that came out of northern Europe, and a different group that came out of southern Europe," says Parker, "which shows herding is not a recent thing. People were using dogs as workers thousands of years ago, not just hundreds of years ago."
Different herding dogs use very different strategies to bring their flocks to heel, so in some ways, the phylogenetic data confirmed what many dog experts had previously suspected, the researchers noted. "What that also tells us is that herding dogs were developed not from a singular founder but in several different places and probably different times," says the study's senior co-author and dog geneticist Elaine Ostrander, also of the NIH.
Understanding dogs' genetic backstory also has practical applications. Our canine compatriots fall victim to many of the same diseases that humans do -- including epilepsy, diabetes, kidney disease, and cancer -- but disease prevalence varies widely and predictably between breeds, while it is more difficult to compartmentalize at-risk human populations. "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," says Ostrander. "Every time there's a disease gene found in dogs it turns out to be important in people, too."
Source: Cell Press [April 25, 2017]