If variety is the spice of life, dogs are ahead of the game. From tiny Chihuahuas to towering Great Danes, from fluffy Chow Chows to the hairless Xoloitzcuintli, our canine companions span every shape and size.
After centuries of selective breeding, the influence on dogs’ bodies is obvious. But now, a new study shows that humans have actually reshaped the canine brain, as well.
For the study, researchers at Harvard University analyzed MRI scans of 62 dogs, representing 33 breeds. Even after accounting for breed size and skull shape, they found significant differences in brain structure.
After determining which parts of the brain varied most across breeds, the scientists identified which functions the areas were responsible for, such as smell or hearing. The team found that these areas “correlated significantly” with common traits associated with each breed.
“These results indicate that through selective breeding, humans have significantly altered the brains of different lineages of domestic dogs in different ways,” wrote the authors.
When dogs are bred, certain traits are selected, such as a small stature and long coat for Yorkshire Terriers, or the lean build of a Greyhound.
“However, it’s important to remember that genetics is not that simple,” says Dr. Lauren Jones, a veterinarian in the Philadelphia area. “Many of these selected physical traits are linked to other physical changes, health conditions and personality traits—some of which are less desirable.”
Responsible breeders perform a variety of screenings and genetic tests prior to breeding. The goal is to decrease the incidence of common breed-specific conditions, such as hip dysplasia, progressive retinal atrophy and heart defects.
“While this is the best way to ensure that future generations of a certain breed are in the best health possible, it is not perfect,” says Jones. “Human intervention in selective breeding can have some unintentional and undesirable consequences.”
Before adding a new pet to the family, it’s important to carefully consider the breed's characteristics.
“If a dog was bred to hunt, expect them to have endless amounts of energy that needs an outlet,” says Jones. “If a breed was purposed as a guard dog, be wary about the potential for aggression-related issues. The genetic component of these traits is rooted deeply.”