In the 1500s, there was a little dog called turnspit whose job was to roast meat. The dog was a widespread kitchen attendant until the mid-1800s, when new tech took the breed's trade. The turnspit was just one of a vast constellation of dog breeds, past and present.
The immense physical variety of dogs makes them among the world’s most diverse species, and likely the one with the greatest range in size. A Pomeranian, for example, might weigh two kilograms, while a Mastiff could tip the scale to 100. So, why is this?
And what does a dog’s breed actually say about them? All dogs descend from ancient wolves that started living around humans at least 15,000 years ago. Dogs are the first domesticated species, by a landslide of thousands of years.
Over time, it's thought that humans began relying on dogs for specific tasks and selectively breeding them for particular traits, fueling the dramatic diversification of dogs planet-wide. By 11,000 years ago, they’d already assumed an array of appearances. And finally, formalized dog breeding took off in Victorian England.
Instead of mating dogs to emphasize their function, people selectively inbred dogs to achieve particular features and established overarching breed standards. But while maintaining specific lines of inheritance and characteristics is important to kennel clubs, breed genetics are complex. In one study where scientists sequenced the genomes of different dog breeds, 10 major groups emerged that roughly aligned with the lineage’s historic working role— from pointing and flushing to scent-tracking and retrieving.
Within different breeds, scientists may be able to identify distinct genetic signatures, but it's difficult to untangle how those genetic signatures actually shape breed-defining traits. This is especially true when it comes to parsing how much a dog’s breed informs their personality, as defined by their consistent behaviors across a range of scenarios. When researchers in one study compared the genetic data from many different dogs, they found about 9% of a dog’s personality traits were attributed specifically to its breed.
Some of the traits in the study that were most heritable seemed to be derived from long-standing predatory behaviors also exhibited in wolves. This is seen in how border collies stalk with their eyes, and how golden retrievers chase and grab-bite. And other traits also seem to have gotten ingrained along the way.
For example, breeds like Portuguese water dogs do tend to be especially comfortable getting wet; retrievers have an aptitude for fetch; and for dogs like huskies, malamutes, and hounds, howling seems habitual. How well a dog responds to human direction was another of the most heritable behavioral traits by breed, with border collies standing out. Other behaviors— including circling before pooping, and how easily provoked or aggressive a dog is— don’t appear to be super breed-specific.
So, while pit bull terriers are widely considered to be more aggressive dogs, this research casts doubt on their reputation. Toy breeds did appear to be more independent and less sociable with other dogs, but non-genetic factors could be at work. For example, smaller dogs might not initiate much play with other dogs because they're small or how they're socialized, and not necessarily due to how their genes wire their brains.
The same study found that, beyond breed, less than 25% of a dog's personality was accounted for by their genes. So, genetics play a role, but they’re not nearly everything. This is also illustrated in service dog breeding programs, which deliberately breed certain dogs based on their temperament.
This yields lots of dogs suited for service— but because of individual variation, some still don't make the cut. As much as humans have heavily tinkered with canine characteristics, dog behavior is shaped by a complex mix of their genes and environment. And breed alone appears to be a pretty poor proxy for all that makes up the personality of a given pup.
