Though dogs and cats are not genetically related, selective breeding is making certain breeds of each species look surprisingly similar. Features like flat faces and large, round eyes are being favored, which is why breeds such as pugs and Persian cats are beginning to resemble each other more than their wild ancestors.
Researchers Abby Drake from Cornell University and Jonathan Losos from Washington University studied the skull shapes of 2,800 cats, dogs, and their wild relatives. Their findings showed that domestic breeds display far more skull variation than wild species because of artificial selection. In fact, the skull of a pug or a Pekingese dog was found to be more similar to a Persian cat than to a wolf or a wildcat.
This shift is driven by human preference. People are naturally drawn to infant-like features—flat faces, big eyes—because they trigger parental instincts. Humans are one of the most helpless species at birth, requiring long-term care. This instinctive desire to nurture extends to pets, making animals with baby-like features seem cuter and more desirable.
While puppies and kittens are self-sufficient much earlier than human babies, breeding animals to appear more infant-like boosts their appeal. This trend is an example of convergent evolution, where unrelated species evolve similar traits due to shared environmental pressures. Though dogs and cats diverged from a common ancestor 50 million years ago, modern breeding practices are pushing their appearances closer together.
Breed standards often use similar language for these desired traits. For example, both Pekingese dogs and Persian cats are bred for noses that sit high between the eyes and a vertical facial plane with no muzzle protrusion.
However, this human-driven evolution comes with health risks. Flat-faced breeds like pugs and Boston Terriers suffer from respiratory issues and can even face life-threatening nosebleeds, which prevent them from flying. Historically, pugs had longer faces and limbs, but selective breeding for flatter features has changed their appearance—and not always for the better.
While many people adore animals that don’t resemble humans, the overall trend of breeding for “cuteness” continues. Yet, from a health perspective, mixing breeds or allowing for natural genetic diversity often results in healthier pets. So, while a stray puppy might lack a pedigree, its genetics could spare it from many of the health problems linked to extreme breeding practices.
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