From a genetic standpoint, dogs offer a lot to explore. We find ourselves in the curious situation of an animal where the breeds exhibit little genetic variety, but the species as a whole is incredibly heterogeneous.
Among mammals, dogs have the greatest genetic heterogeneity. This is particularly evident in their phenotype, the expression of genes in the body and behavior.
A 2004 study was able to correctly assign 99% of 414 dogs from 85 different breeds to their correct breed using microsatellites (short, repeating sequences of DNA).
In relation to this, genetic studies in dogs using microsatellites have been almost completely replaced by the use of SNPs (single nucleotide polymorphisms) in dogs.
By 2015, nearly 20 million different SNPs had been registered in this species.
We are talking about a species so diverse that the life expectancy of some breeds is twice that of others.
The very history of breeds and their origins is highly varied.
Modern Breeds and Selective Dog Breeding
Most dog breeds belong to the so-called “modern breeds.” These are breeds that have emerged since the year 1800 through artificial crossings and have a significant detail: most breeders had aesthetic and physical objectives when developing them.
It was during this time that dog shows and competitions began to emerge. The working dog started to be replaced by the modern dog.
Before this, dogs were selected for three main functions: hunting, protection, and herding. These three functions had emerged from the natural hunting behavior of the wolf, their ancestor.
The strict acceptance criteria and breed standards further encouraged the constant pursuit of specific canine physical traits. Traits that served no other function than to please the breeder.
More than 40% of dog breeds originate from the United Kingdom, France, and Germany. If we consider the whole of Europe, more than 80% of dog breeds have their origin on this continent. Clearly, the objective was not to have many different herding dogs.
Additionally, compared to the so-called basal and/or ancient breeds (terminology in this field changes frequently), these modern breeds are more genetically similar. They have been repeatedly crossed in the pursuit of desired physical traits, leading to homogenization among them.
The result is interesting. We find that many dog breeds have significant genetic similarities but maintain distinct and stable regions of the genome.
These regions often carry information for specific traits, the traits that breeders have fixed in the breed through selective breeding. These regions, by the way, allow genetic tests to assign the animal’s breed.
If the main interest in these new breeds was specific physical characteristics (often with aesthetic interest), behavior was relegated to a secondary concern.
Canine Behavior and Human Influence
When comparing dogs to wolves, there are behavioral differences between the two species, all due to human influence.
The first and most obvious difference is the wolf’s distrust of humans. Dogs are less cautious, less timid, and more playful and relaxed than wolves.
Dogs have also learned to understand human language. We don’t mean speaking to them; they are not linguists, but they can interpret facial expressions and body signals.
Wolves reach adulthood earlier, are more intelligent, and do not depend on human presence for anything.
Of all the traits dogs have, docility has the highest heritability. It makes sense. The most important aspect of dogs, in general, was their ability to understand and obey human commands.
Once dogs were obedient and the new breeds were used more for companionship and exhibition than for work, was there an interest in developing specific behavioral traits?
It seems not. A recent study (recent if you are reading this in 2024 when this article was published) has shown that behavioral traits within the same breed vary among individuals.
Therefore, a dog’s breed would not be a reliable predictor of its behavior.
The Heritability of Behavior
For this study, more than 18,000 dog owners were interviewed, half of them with purebred dogs, and more than 2,000 animals were sequenced.
It is true that most behavioral traits were hereditary; the issue is that they were very similar across breeds. What does it matter to inherit certain traits if they are shared with other breeds?
There were exceptions. For example, the docility of an animal, the trait we mentioned earlier as the most heritable. In this case, the breed allowed for more accurate predictions.
Behaviors involving movement patterns were the most inherited, such as retrieving/collecting things.
Other behavioral traits were inherited due to the animal’s characteristics, so calling them “heritable” is somewhat questionable. The way a dog sits or lies down is related to its physique, which in turn depends on the breeds that make it up.
However, in other traits such as agonistic threshold, knowing the animal’s breed had a value close to zero. The individual experiences of each dog, in the environment in which it had developed, had a greater weight.
Agonistic threshold, in brief, can be understood as how easily an animal can strongly dislike you.
Another detail is that there were always exceptions. Among Labrador Retriever owners, 8% reported that their pet howled sometimes or always. Among Greyhound owners, 7% described their dogs as burying their toys, while the rest said theirs never did.
No behavior was exclusive or unique to a breed.
Additionally, consider how difficult it would be to predict behavior based on breed in a mixed-breed dog. It is estimated that, worldwide, more than 80% of dogs are mixed breeds.
Even in first-world countries like the United States, half of the animals had more than one breed in 2018.
In summary, in modern dogs, the focus of their artificial breeding has been aesthetic, with the search for physical traits predominating above all. This has made predicting a dog’s behavior based on its breed less reliable.
Dogs within the same breed show behavioral variability, demonstrating that, currently, the animal’s environment is the main determining factor of its behavior.
However, this does not exclude the genetic aspect. There are behavioral traits that are heritable and will influence the animal. If your dog’s ancestors have spent 500 years retrieving game for their owner, it’s normal for something to persist. Simply, the breed is a lesser determinant than previously thought.
When you do the dog DNA test from Koko Genetics, remember that the most inherited trait they have is trusting us. Do not betray a trait embedded in their genome.