It may be hard to see that the Chinese crested dog is descended from the wolf, but it’s easier to grasp that two poodles of different sizes are related. In her dissertation presented on May 3, Susanne Björnefeldt, at the Department of Evolution, Genomics, and Systematics at Uppsala University, shows that dogs of the same breed differ more genetically than was previously thought.
The wolf is the first animal that humans domesticated. Even though all dogs descend from the wolf, today dogs occur in more variants than any other mammal. These variations are not only the result of breeding, but also of the comfortable life dogs lead, a life that has entailed genetic changes. We might expect dogs to be genetically different from those of another breed, but we might also be led to believe that they are relatively similar within a single breed.
But in fact dogs of the same breed are genetically more different than we thought, according to Susanne Björnefeldt. She mentions the poodle as an example: it is genetically divided into five groups, although kennel clubs divide the poodle into four distinct groups.
In her dissertation Susanne Björnefeldt has primarily compared the mitochondrial DNA of the dog with that of the wolf and found that more protein changes have taken place in dogs over a shorter period than in the case of their wolf ancestors. Dogs have mutated more rapidly than wolves. Many of these mutations can be harmful to the animal. Whereas wolves have eliminated most altered characteristics through natural selection (a wild wolf with inferior characteristics will not be allowed to mate), dogs have been able to pass on their mutations, for better or worse.
“One advantage is that it is easier to use the dog as an experimental animal in scientific studies in order to facilitate the search for pathogenic genes. A drawback, however, is that thoroughbred dogs are more susceptible to diseases,” says Susanne Björnefeldt, who is the owner of two Welsh Springer spaniels. “One of these dogs, Higgins, has actually contributed to my work by donating hair to a study in which I determined what method works best for extracting DNA from a hair,” says Susanne Björnefeldt.