A new study may help us understand our canine companions a bit better. Scientists at the National Institutes of Health say they’ve uncovered some of the ways that genes can influence the behaviors of certain breeds, such as dogs meant to herd livestock.

For about two decades, a team led by Elaine Ostrander at the National Human Genome Research Institute has been working on the Dog Genome Project. The ultimate goal of the project is to get a grasp on how genetics affect everything from a dog’s vulnerability to illness to the shape of their bodies. In their new study, published Thursday in Cell, her team did a deep dive into the genetic underpinnings of doggy behavior.

“Our study analyzed the genomes of thousands of dogs from hundreds of breeds and populations across the world in order to uncover the genetic basis of behavioral diversity across modern dogs,” Ostrander said in an email to Gizmodo. “We wanted to understand what in their genes makes sheepdogs move livestock, terriers kill vermin, hounds help us hunt, etc.”

Overall, they studied the genes of over 4,000 purebred dogs, mixed-breed mutts, semi-feral dogs, and even wild cousins of the domestic dog. Based on this analysis, they identified 10 genetically distinct lineages. The team noticed that breeds with similar behavioral traits often grouped together within these lineages, such as dogs that hunt primarily using their sight compared to hunting dogs that rely on scent. They then cross-referenced what they found with survey data from more than 46,000 purebred dog owners.

From there, Ostrander said, the team “determined that each lineage has their own unique mix of behavioral tendencies that make them good at the jobs they were originally kept for.” Terrier breeds, for example, tend to be more enthusiastic in chasing down potential prey, which makes sense, since these dogs were originally bred to chase down pests. Finally, the team tried to find specific genetic variations that might drive the behaviors of certain breeds, including those that affect early brain development.

“For example, among sheepdogs, a behaviorally unique collection of breeds historically used to herd livestock, we identified variants associated with genes controlling axon guidance, a process that lays the foundation of connectivity in the brain that modulates complex behavioral traits,” Ostrander said. These variants, some of which have been linked to attention-deficit hyperactivity disorder in humans, might help explain why sheepdogs tend to become incredibly focused while herding.

While humans have domesticated many animals, dogs were likely the first. And they’ve since become perhaps the most diverse creature around, especially in the last couple hundred years, when intentional dog breeding became widely practiced (a pug looks very little like a husky, for instance). But importantly, Ostrander and her team’s research also indicates that many of the genetically driven behavioral differences we see in dogs now weren’t created by modern-day breeding.

“Instead, early dog ‘types’ likely rose to prominence in different parts of the world over thousands of years as humans kept them for different purposes,” Ostrander said. “Our work shows that as humans began to categorize dogs into ‘breeds’ a few hundred years ago, they were preserving single snapshots of dog genetic diversity that existed in a certain place at a certain time, and that this genetic diversity was relevant to behavior.”

This work is only the beginning for Ostrander’s team. They plan to continue looking for specific gene variants that drive breed behaviors. The same unique approach developed for this study should also allow them to study how a dog’s genetics can influence other complex traits, including their risk of certain diseases. And just as dogs have done for us so many times in the past, what we learn from this research could someday help humans, too.

“Dogs and humans get the same diseases, those diseases present in much the same way, and anything we learn about canine genetic health impacts our understanding of our own susceptibility to disease,” Ostrander said.