July 14, 2025
When choosing a dog, should you go for a purebred or a mixed breed? Many believe that purebred dogs are predictable in looks and behaviour, while mixed breeds are healthier and stronger. But is it really that simple?
The debate between purebred and mixed-breed dogs is often shaped by myths rather than facts. In reality, every dog is an individual, influenced by a complex combination of genetics, environment, and life experiences. To truly understand the differences, we need to look at the origins of dog breeds and how human intervention has shaped them over time.
Contrary to popular belief, purebred dogs did not come first—mixed breeds did. The domestic dog (Canis lupus familiaris) has existed for thousands of years, evolving alongside humans. Early dogs were not selectively bred for specific traits; instead, they adapted naturally to their environments, with humans favoring those that proved useful for hunting, guarding, or companionship.
Early dogs adapted naturally to their environments, thriving through survival traits. But in the past 150 years, selective breeding has dramatically reshaped dogs to meet human aesthetic standards—often at a cost.
That intense selective breeding took hold, leading to the establishment of strict standards for physical traits and pedigrees. This modern approach to breeding has accentuated specific features in many breeds. In fact, comparing photos of the same breeds from the early 1900s with those of today reveals significant changes. Traits such as the increasingly flattened faces of Bulldogs and Pugs, or the elongated bodies of Dachshunds, are clear examples of how selection has dramatically altered the dogs’ appearance—sometimes even compromising their health.
While purebred dogs are often seen as the “standard,” it’s important to remember that their ancestors were once mixed-breed dogs. In a way, mixed-breed dogs represent the original, natural state of canine diversity.
When discussing purebred dogs, the focus is often on their physical traits, but selective breeding has also profoundly shaped their behaviour.
By selecting for specific physical characteristics, we inevitably influence brain
development. Conversely, when breeding for specific behaviours, we also shape their
physiology, including the structure of their brain.
The shape and size of the skull adapt to accommodate brain growth, which in turn influences cognitive and behavioural tendencies.
However, brain development is not solely dictated by genetics. Experiences and external stimuli can influence how certain genes are activated or suppressed over time, a process known as epigenetics. This means that while a dog’s inherited traits set a foundation, their behaviour and even some physical traits can change across generations due to lifestyle, environment, and training.
Many breeds were developed for specific tasks, leading to distinct neurological and behavioural traits. For instance, Border Collies, bred for high-energy work, have a brain chemistry rich in dopamine, which makes them highly responsive, driven, and motivated by movement. Guardian breeds, on the other hand, tend to have lower dopamine levels, making them more independent and reserved, with a natural inclination toward vigilance, and less prone to compulsive behaviours. These differences are not just behavioural but have a biological basis, influencing how each breed processes information and reacts to stimuli.
If these dogs are unable to express the behaviours for which they were bred—or if they are not
given alternative outlets that provide similar satisfaction—they can develop compulsive or maladaptive behaviours. Herding breeds, for example, may become fixated on chasing moving objects, such as cars or children, or develop repetitive behaviours like spinning or shadow-chasing. Guardian breeds may exhibit excessive alertness, barking, or territorial aggression, unable to “switch off” their protective instincts. Retrievers, originally selected to carry game, might develop an obsessive need to carry objects or resort to destructive chewing if their need for retrieval is not met.
What is often mistaken for stubbornness or disobedience is, in reality, a response to unmet biological needs. Dogs that cannot fulfil their instincts experience frustration, which can escalate into anxiety, compulsions, or even self-destructive behaviours.
Understanding a breed’s natural instincts is crucial in providing an environment that meets their
needs. Through structured training, enrichment activities, and alternative tasks that mimic their original purpose, we can ensure their well-being and prevent behavioural disorders.
Loss of Genetic Diversity and the Rise of Hereditary Diseases
For thousands of years, dogs have adapted naturally to different environments, developing traits that increased their survival and functionality. However, modern selective breeding has dramatically changed this process, often reducing genetic diversity instead of enhancing it.
Most purebred dogs today come from a limited gene pool, meaning they inherit a high percentage of the same genetic material from their ancestors. This lack of variation weakens their natural ability to resist diseases and adapt to environmental changes. Over time, it has led to a dramatic increase in hereditary conditions, some of which were rare or even nonexistent in earlier generations.
For instance, heart diseases are alarmingly common in certain breeds, such as Cavalier King Charles Spaniels, while Dalmatians frequently suffer from congenital deafness due to genetic mutations that spread within the breed.
Large breeds like Great Danes and Saint Bernards are prone to bone cancers and joint disorders, while small breeds often experience neurological conditions linked to skull deformities.
The irony is that, rather than preserving a “superior” lineage, excessive inbreeding and selective breeding have made many breeds genetically weaker, shortening their lifespans and lowering their quality of life.
To maintain breed purity, many pedigree dogs are bred within a restricted family lineage. In some cases, direct relatives—such as father and daughter or siblings—have been mated to “fix” certain desirable traits. This practice, known as inbreeding, dramatically increases the risk of inherited disorders, as harmful genetic mutations become more concentrated within the breed.
The consequences are severe. Dogs from highly inbred lines often suffer from:
Inbreeding doesn’t only affect physical health—it also impacts behaviour and temperament.
Studies have shown that inbred dogs are more likely to develop anxiety, excessive
fearfulness, and compulsive behaviours. Some lines of working breeds, for example, show
extreme sensitivity to stress, making them unsuitable for family life.
Despite these risks, some breed standards continue to encourage exaggerated features that
require tight genetic control, further limiting the gene pool. This raises a crucial question:
Is maintaining a “pure” bloodline worth the suffering it causes?
The quest for aesthetic perfection in dog breeding has led to the emergence of breeds with exaggerated physical features. While these traits may align with breed standards and appeal to human preferences, they often come at a significant cost to the dogs’ health and well-being.
These examples underscore the ethical dilemma in breeding practices that prioritize appearance over health. While breed standards aim to preserve specific traits, they can inadvertently encourage the perpetuation of harmful characteristics, leading to a diminished quality of life for the dogs.
Inbreeding doesn’t only affect physical health—it can also alter dogs’ social and communicative
abilities. Research has shown that:
For example, English Bulldogs often struggle to convey clear visual signals due to their facial
folds and muzzle structure.
Limited genetic diversity has been linked to…
For example, some heavily inbred Dobermann lines are more prone to obsessive-compulsive disorders.
Addressing the risks of inbreeding requires a shift in breeding priorities — one that values genetic health and diversity over rigid adherence to breed standards.
Outcrossing: Introducing new bloodlines by carefully breeding dogs outside of tightly controlled pedigrees can significantly reduce the risk of inherited disorders. Outcrossing broadens the gene pool, improving immune resilience, reducing the prevalence of genetic mutations, and promoting healthier litters.
Genetic Testing: Advances in genetic screening allow breeders to identify carriers of harmful mutations. Responsible breeders can use this information to make informed decisions, selecting pairings that minimize the likelihood of passing on hereditary conditions.
Rethinking Breed Standards: Some progressive breed clubs have started adjusting their standards to discourage extreme traits that compromise canine welfare. Encouraging breeders to prioritise function and health over aesthetics can foster healthier generations of dogs.
By embracing these strategies, breeders can break the cycle of inherited suffering and help restore the robust vitality that dogs naturally possessed before artificial selection narrowed their genetic diversity.
While selective breeding has led to exaggerated and often harmful physical traits, nature follows a different path. Dogs that develop without extreme artificial selection tend to have more balanced anatomies, supporting better overall health and adaptability.
Mixed-breed dogs, often resulting from generations of natural selection or diverse genetic backgrounds, generally exhibit more proportional body structures. This balance reduces the risk of many hereditary diseases seen in purebred dogs, such as hip dysplasia or brachycephalic airway syndrome. Their broader gene pool also promotes hybrid vigour — a natural advantage where greater genetic diversity strengthens immune function and lowers the likelihood of inherited disorders.
Unlike selectively bred dogs, whose traits are often exaggerated for appearance, naturally adapted dogs retain functional characteristics that enhance their survival. Their skull shapes allow for efficient breathing, their leg proportions support optimal mobility, and their coats align with their environmental needs rather than human preference.
This contrast highlights a crucial point: while human intervention in breeding has shaped many of the dog breeds we recognize today, it has often come at the cost of their well-being. In contrast, dogs with more naturally adapted forms demonstrate how balanced physiology supports a healthier, more resilient life.
Mixed-breed dogs are often praised for their robustness, but what exactly does this mean? The key lies in their genetic diversity. With a broader gene pool, these dogs are less prone to the inherited disorders commonly found in purebred dogs. Conditions such as hip dysplasia, heart defects, and certain eye diseases are typically less frequent in mixed-breed populations.
This genetic advantage, known as hybrid vigour, also supports stronger immune systems, giving mixed-breed dogs better resilience against infections and chronic illnesses. Additionally, their more balanced body structures often result in improved joint stability, respiratory function, and overall mobility — factors that contribute to a healthier and more active life.
Interestingly, this enhanced genetic variety can also influence behaviour. While temperament varies greatly between individuals, mixed-breed dogs often display adaptable and versatile traits, making them well-suited for a wide range of lifestyles.
For dog owners, these benefits can translate into fewer veterinary expenses and a greater chance of enjoying many happy, healthy years with their canine companion.
Choosing a dog is a long-term commitment that goes beyond appearance or breed popularity. While purebred dogs may offer predictability in terms of size and temperament, they often come with inherited health and behavioural challenges due to selective breeding. On the other hand, mixed-breed dogs tend to have greater genetic diversity, which can contribute to better overall health and adaptability.
Regardless of the choice, prospective owners should research thoroughly, considering not just the dog’s physical and behavioural traits but also their own lifestyle and ability to meet the dog’s needs. Understanding the genetic and environmental factors that shape a dog’s behaviour and health can help prevent frustration, unrealistic expectations, and, most importantly, unnecessary suffering for the dog.
It’s also important to remember that, unlike us, dogs don’t get to choose their families. This makes it our responsibility to ensure they are truly cared for—not just in terms of food and shelter but in making them feel like valued members of the family because, in the end, whether purebred or mixed, what truly matters to them is a sense of belonging.
For a deeper understanding of the ethical concerns surrounding fashionable dog breeding and
its impact on canine health, see:
Ethical Concerns about Fashionable Dog Breeding (PUB)
Canine Genetic Diversity and Its Impact on Health (PMC)
The effect of inbreeding, body size, and morphology on health in dog breeds
(ResearchGate)
Brachycephalic Airway Syndrome in Dogs (petmd.com)
Flat-faced (brachycephalic) dog breeds (bluecross.org.uk)
Inbreeding Impact on Litter Size and Survival in Selected Canine Breeds
(The Veterinary Journal)
The Myth of Hybrid Vigor in Dogs (Institute of Canine Biology)
https://pubmed.ncbi.nlm.nih.gov/38473141/
https://pmc.ncbi.nlm.nih.gov/articles/PMC8412370/
https://www.petmd.com/dog/conditions/respiratory/brachycephalic-airway-syndrome-dogs?utm_source=chatgpt.com
https://www.sciencedirect.com/science/article/abs/pii/S1090023314004559
https://www.instituteofcaninebiology.org/blog/the-myth-of-hybrid-vigor-in-dogsis-a-myth
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