You need only look at a hulking Great Dane and a tiny chihuahua side-by-side – both having evolved from wolves – to understand how much selective breeding by humans has shaped the huge variation of dog types.
Humans have been molding the characteristics of dogs for about 15,000 years, since dogs were first domesticated, producing distinct breeds for different tasks such as hunting, herding, guarding, or companionship.
Now comes a new study in the Journal of Neuroscience that shows just how much we have shaped dogs’ brains as well as their bodies. The study found that the structure of a dog’s brain varies greatly between breeds, depending on what task or temperament the dog was bred for.
The scientists performed MRIs (medical imaging) on 62 dogs of both genders within one of 33 breeds identified by the American Kennel Club, such as Golden Retrievers, greyhounds and Bichons Frises. They were further grouped into breed groups known for specific tasks such as hunting or herding.
The scientists concluded that humans have significantly altered the brains of domestic dogs in a myriad of ways. The scientists looked at factors such as the overall size of the body or brain, the shape of the skull, and how the brain networks are organized.
Dogs bred for sight hunting, such as the Whippet, had a more developed region of the brain that supports movement, eye movement, and spatial navigation, for example, while dogs bred for scent hunting, such as the Beagle, had a more developed section of the brain for olfactory processing.
Here are some of their key findings:
- Differences in dogs’ brain anatomy and nervous systems are plainly visible across breeds, depending on whether the breed was bred for sight hunting, scent hunting, guarding or companionship.
- Most of the changes have occurred fairly recently in evolutionary time, say in the past few hundred years when modern breeds were developed.
- The sizes of dogs’ brains don’t exactly correspond to their body size. Yes, larger dogs have larger brains, but a dachshund’s brain takes up most of the available skull space, the Golden Retriever has noticeably larger sinuses.
- Smaller-bodied dogs, such as Lhasa Apsos, have more spherical brains than large breeds like Saint Bernards.
“These results tell us something fundamental about our own place in the larger animal kingdom: we have been systematically shaping the brains of another species,” they conclude.
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