Few animals are so tightly linked to domestication as dogs. While we’ve domesticated a handful of species for agriculture, our relationship with canines predates even that, starting with man and dog hunting side by side more than 10,000 years ago.
According to archeologist Diane Perlov, senior vice president for exhibitions at Los Angeles’ California Science Center, both species would have recognized that the other was good at hunting. Humans and dogs/wolves are pack animals, meaning they are social creatures that thrive on cooperation and relationships with others. It’s how we each evolved as hunters, and so the partnership is understood to have started off as a match made in evolutionary heaven, but whether or not wolves offered their services in exchange for security or humans made a conscious effort to domesticate them for their own benefit is one major question that remains unknown.
But of all the things we’ve learned through the years of domestication’s influence on the canine evolutionary process, new findings from Harvard researchers show just how profoundly humans have shaped dogs as we know them today. Literally. According to the research of Erin Hecht, assistant professor of neuroscience in Harvard University’s Department of Human Evolutionary Biology, selective breeding of canines has changed the overall shape of dogs’ brains. By intentionally and selectively breeding them for specific behaviors, we’ve actually molded and shaped the brains of our own best friends.
As mentioned, our partnership with dogs goes thousands of years back in history, but the practice of selective breeding for desired characteristics and traits doesn’t run as deep into the history books. It’s believed there are three basic categories of dogs that people started breeding dogs to fit into — livestock guardian dogs, hunting dogs, and sighthounds. People would recognize the specific characteristics and traits of certain dogs that fit best into the tasks associated with each category, and eventually started intentionally mating dogs with certain desired characteristics in order to encourage those characteristics in the offspring. The result of this became hundreds of unique breeds that were developed. And the further we moved from the hunter-gatherer life and closer to agriculturally-dependent societies, the more dogs were bred to be smaller and more docile as a way for us to live together comfortably. With the development of breed clubs and kennel clubs in the 19th century, the focus of selective breeding took a sharp turn toward many aesthetic characteristics rather than functional/behavioral characteristics. The newfound popularity of dog shows gave way to breeders preserving very specific mutations like hair color and texture, face shape, limb length, and so on. And with that little history lesson, we can start to wrap our minds around just how the development and influence of breeding practices over generations started to impact something as significant as brain shape.
Hecht used MRI scans from 63 dogs of 33 breeds, finding neuroanatomical features that correlated to different behaviors in dogs, like hunting, guarding, herding, and companionship — many of those same behavioral traits man would have selectively bred for in the initial stages of the practice.
“In my career so far, there have been a couple of times when you look at the raw images (MRI scans) and know there is something there even before you do statistics. This was one of these times,” she said. “I was like ‘Holy cow! How come no one else has done this?’”
Hecht’s work actually came as a side note to her studies of human brain evolution. While watching a nature show, she learned about selectively bred Russian foxes and wondered why the scientist on television was speaking so much about genetics and evolution but not about neuroscience.
From there, Hecht’s first study actually started with half a dozen brains of domesticated foxes and relying on help from a veterinary neurologist at University of Georgia College of Veterinary Medicine who shared dozens of MRI scans. Hecht’s initial data from those two factors were enough to earn her funding for a more in-depth study from the National Science Foundation. With her team, Hecht examined variability in brains by structure and shape and was able to pinpoint six networks of the brain where anatomy correlated with types of processing which are important for different breeds: reward, olfaction, eye movement, social action and higher cognition, fear and anxiety, and scent processing and vision. This taught them things like where skills for hunting, for example, are accessed and located within brain function — something previously assumed to be associated with the anatomy of the olfactory bulb (a neural structure of the vertebrate forebrain involved in the sense of smell).
“Rather, this skill was linked to higher-order regions that are involved in more complex aspects of scent processing,” she said. “It’s not about having a brain that can detect if the scent is there. It’s about having the neural machinery to decide what to do with that information.”
To the common person who doesn’t understand the complexities of neuroscience, there are obviously a lot of “chicken or egg” questions left on the table. For example, does selective breeding ensure an animal is born with desired traits and an innate skill, or have humans simply been giving dogs a greater capacity for the skills we want them to display?
“Border collies are amazing at herding, but they aren’t born knowing how to herd,” Hecht explains. “They have to be exposed to sheep; there is some training involved. Learning plays a crucial role, but there’s clearly something about herding that’s already in their brains when they are born. It’s not innate behavior, it’s a predisposition to learn that behavior. That’s analogous to what goes on with humans with language. They don’t pop out of the womb being able to speak, but clearly, all humans are predisposed in a very significant way to learn a language. If we can figure out how evolution got those skills into dog brains, it might help us understand how humans evolved the skills that separate us from other animals.”