Your dog's genes, but not necessarily its breed, play a big role in its behavior

Your dog's breed may not dictate its behavior, though genes do play a role, a study of the genomes of 4,000 purebred, mixed-breed and wild dogs has revealed. 

In comparing the DNA data of so many animals, researchers found that genetic variations appeared in clusters around different types of dogs. These clusters contained dog breeds that all had one thing in common: the role their ancestors played in human history. 

"Humans have employed dogs for thousands of years to perform tasks such as herding livestock, killing vermin, hunting, pulling loads, guarding, and companionship," the study authors wrote in their paper. "To produce dogs that will [perform these roles] reliably, humans have selectively bred toward a variety of behavioral ideals." 

This selective breeding began around 2,000 years ago, but humans began classifying dog breeds much more recently. The names we use for modern breeds are less than 160 years old, "a blink in evolutionary history compared with the origin of dogs more than 10,000 years ago," the authors wrote in the paper, published Dec. 8 in the journal Cell. 

Instead of grouping dogs by breed, the DNA analysis revealed 10 genetic lineages from which modern dogs descend: the scent hound, pointer-spaniel, retriever, terrier, herder, sled, African and Middle Eastern, Asian spitz, dingo and sight hound. Within these 10 groups, the researchers found distinct genes — and common behaviors. 

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Terriers had more dog-directed aggression and a higher predatory drive. This makes sense in light of the history of the terrier breeds, which were generally used for hunting vermin and in the "sport" of dogfighting. Companion and toy dogs showed high levels of fear of dogs, humans and different situations. Scent hounds demonstrated anxiety-related behaviors, which the authors suggested could be caused by the hunting dogs' need for acute sensitivity to the movements of their targets. 

Herders, which include dogs that were bred for working with sheep and cattle, were some of the most easily trained, and they had decreased levels of aggression and predatory drive. Owners of these dogs commonly report the animals' tendency to herd, even if they've never been trained to work. Sheepdogs, for example, can take to rounding up their toys or even grouping small children. 

As well as a strong herding instinct, the original herders needed to have precise control over their movements, as subtle changes in position can drive a herd in a different direction. But whether these behaviors, shown in generations of herding dogs, had a basis in the dogs' DNA was of particular interest to study first author Emily Dutrow, a postdoctoral fellow at the National Human Genome Research Institute.

Dutrow and colleagues found specific genes in herding dogs' DNA that relate to brain activity. These included genes that link to motor control and vision, as well as one that has been associated with a mothering instinct in mice to gather their litter. 

The study also found genes relating to the heart, the digestive system and other parts of the dogs' physiology, as well as many bits of DNA that are inactive or non-coding, or "junk DNA." While some of these genes were found more commonly in some lineages than in others, the research doesn't directly prove a link between specific bits of DNA and certain behaviors, said Kathleen Morrill, a genomics researcher at the University of Massachusetts. 

Earlier this year, Morrill co-authored a paper on dog genetics that also found common behaviors across large groups of dog breeds. In showing that very few traits are breed-specific, Morrill's paper broke down many of the stereotypes about dog personalities. Behavior, Morrill told Live Science, emerges from a complicated interaction of genes and environment that we still don't understand. 

"It's not as simple as 'all retrievers have a retrieving gene,' or that broad behaviors, like aggression, are genetically ingrained into certain breeds," Morrill said; these studies illustrate the "genetic complexity of dogs."