How Years Of (Human-Driven) Selective Breeding Has Shaped Your Pooch's Brain

The structure of the greyhound's brain suggests it is receptive to rewards and has a keen sense of movement. Klaus Hertz-Ladiges/Shutterstock

From Toto the Cairn Terrier to the entire cast of 101 Dalmations and Instagram's favorite pooch, Doug the Pug, there are now more than 340 dog breeds in existence – all varying in color, shape, and size. But it's not just their looks that set them apart from one another. According to a study recently published in the journal JNeurosci, years of selective breeding has molded the structure of their brains. These variations can be correlated to certain traits and functions – whether that be hunting or companionship.

Humans have been domesticating dogs for the last 15,000 years, but it was only during the Victorian era that the concept of dog breeds really started to take off. In the 1840s, there were just two recognized types of terrier. By the turn of the 20th century, there were 10 and today, there are 27. "Gun dogs" like the golden retriever and Irish setter can also be traced back to Victorian England when developments in firearm technology created a demand for these huntsmen-helping canines.

But while they might both be Victorian in origin, the Yorkshire terrier and Irish setter were each bred to fulfill a different function and that process has had a lasting impact on their descendants, researchers have found.

The team, led by Erin Hecht at Harvard University, scanned the brains of 62 pet dogs representing 33 dog breeds. The results show that there are surprisingly high levels of variation in morphology rarely seen in nature, but a dog's brain size does not necessarily reflect its body size. 

What's more, the researchers were able to build maps of six neural networks that are associated with different traits or behaviors (stress response, movement, sense of smell, etcetera) and can be linked to different functions (companionship, vermin control, scent hunting, herding, etcetera). These networks positively correlated with characteristics applied to certain breeds, as per the American Kennel Club. Phylogenetic analysis shows the majority of brain structure adaptations have taken place in the terminal branches of the dog phylogenetic tree, which strongly implies the changes are the result of recent – human-driven – selection pressures. 

And so, a dog bred for police work (think: German shepherds, rottweilers) might show strong correlations in networks associated with olfaction and vision, whereas a dog bred for sport hunting (a pit bull, for example) might show strong correlations in those associated with fear, stress, and anxiety.  

The study authors note that selection pressures may be waning as dogs are increasingly bred to be house pets and not working animals, pointing out that previous studies have found behavioral differences between pooches used as pets, show dogs or working dogs – even when they belong to the same breed. The individual dogs recruited for the study, therefore, may show lower (or more relaxed) correlations to these various adaptations. 

The researchers are hoping to better understand what might lead to differences between "high performers" and "low performers" within the same breed, and plan to build on these findings by looking at how other aspects of the brain might vary between breeds, reports the Washington Post.

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