Dogs have been in our lives for at least 10,000 years. At first, dogs did not look like today’s common breeds — these appeared only around 160 years ago, or about 50 to 80 dog generations. Back then, dogs mostly stuck around humans for their food scraps and shelters. However, around 2,000 years ago, humans started to selectively breed dogs to perform tasks such as hunting, herding, and guarding. Our focus on breeding changed during the Victorian era of the 1800’s when humans started selecting dogs for specific physical features, such as the short legs in corgis, and to produce genetically pure lineages.
Over the past 160 years, humans have believed that certain breeds have inherited behavior and temperament from their ancestors. Modern breeds that came from guard dogs are thought to be vicious and unsociable with humans while those that came from herding dogs are thought to be highly responsive to human commands. These and many other behavior traits have been assumed without much study.
However, we know that heritage does not control how we behave, so why should it control dogs? We even go so far as to give dogs sophisticated human medicines like psychiatric drugs to help them live happily. This connection between behavior, genetics, and how we provide medicine caught the attention of a group of USA-based researchers who wanted to use dogs as a model organism for understanding this complicated intersection.
The researchers needed to collect a lot of information on dogs from across the world in order to learn what small differences in genetics might be connected to behavior. To do this, the team developed an open data collection resource called Darwin’s Ark, which anyone can join, and asked pet owners to fill out surveys on the physical and behavioral traits of their furry companions.
From the 18,385 dogs whose data was entered, 9,009 were purebred while the remainder were mutts or otherwise had mixed heritage. Of all these dogs, owners answered roughly 100 questions per pup. This generated a lot of data that the researchers broke down into eight behavioral traits: human sociability, arousal level, toy-directed motor patterns, biddability (how well they listen to their owner), agnostic threshold (how easily they are provoked), dog sociability, environmental engagement, and proximity seeking (how affectionate they are).
Using these eight behavioral traits, the researchers divided 16,522 dogs into groups and of those dogs, 1,967 were selected for the experiment, which used a technique called whole genome sequencing. This technique uses the chemistry of DNA, the molecules that make up our genes, to learn the makeup of each gene and what differences are between a gene in Dog A and that same gene in Dog B.
By looking at these gene differences, the team verified that purebred dogs have fewer genetic differences than mutts do. This makes sense as mutts have genes from many different breeds, all with their own markers, while purebreds have almost the same genes as one another and only the markers of a single breed.
With these gene markers in mind, the team next compared the genetic variation between these dogs with their survey results. Immediately, it was clear that different physical traits were controlled by differences in genetics. Things were not as clear when the team looked at behavioral traits. Some behavioral traits, such as human sociability, biddability, and toy-directed motor patterns, seemed to be about 25% explained by the genetics of a dog. So while certain behavioral traits were more common in some breeds, there was a lot of variation that demonstrated that breed did not control behavior. That being said, some specific traits were more heritable, such as the urge to fetch, which was 52% connected to ancestry.
The team tried to expand this study to focus on genes expressed in the brain in order to investigate different neurological disorders and psychiatric conditions. However, after comparing the genes of dogs with survey questions such as, “How often do they howl,” or ,”How often do they get stuck behind furniture,” the researchers were unable to find a clear pattern. Many of these genes seem to connect with behaviors, but not quite strongly enough to make large scale conclusions about neurological traits and disorders.
As more people access Darwin’s Ark and take part in this survey, the team hopes to expand their study and create larger data sets. As the data set increases, the team will come back to some of these studies and further our understanding of genetics and the mind and ultimately hope to use our so-called best friends to better understand ourselves and biology.