Why Some Dogs and Cats Are Growing More Infant‑Like—and More Alike: Study Finds

Selective Breeding Is Making Some Dogs And Cats Look More Similar

Some modern dog and cat breeds are beginning to resemble one another because humans have selectively bred them for the same facial traits. Features such as a shortened muzzle, upturned nose and very large eyes — traits that echo human infants — are increasingly common in certain purebreds, producing an uncanny resemblance between, for example, pugs and Persian cats.

Evolutionary biologists Abby Drake (Cornell University) and Jonathan Losos (Washington University) analyzed roughly 2,800 skulls from domestic dogs, domestic cats and their wild relatives. They found that skull shape varies more among domesticated animals than wild ones, reflecting the effects of artificial selection by breeders. When they compared skulls across species, the similarity between some dog and cat breeds surprised them.

“The skulls of a pug or a Pekingese and a Persian cat are more similar to each other than either is to their ancestors, the wolf and the North African wildcat,” Losos said in a press statement.

Drake and Losos attribute this cross-species resemblance to human aesthetic preferences. People tend to favor faces that look infant‑like — a small, upturned nose, large eyes and a shortened face — because those cues activate nurturing instincts. Humans are among the most altricial species, meaning human infants are highly dependent on caregivers for a long time. Those baby‑like features reliably trigger caretaking responses in adults.

By contrast, puppies and kittens are relatively precocial: they can move, explore and cause household chaos within weeks of birth, while human babies typically do not begin crawling until around seven months. Still, breeds that project infantile features appear cuter to many people and have therefore been repeatedly selected for by breeders.

Convergent Evolution Driven By Humans

The appearance of similar facial features in unrelated animals is an example of convergent evolution, where distinct lineages develop comparable traits in response to similar selective pressures. Canids (dogs) and felids (cats) diverged from a common ancestor roughly 50 million years ago, so the modern resemblance among some breeds reflects human‑imposed selection rather than close kinship.

Breed standards for certain dogs and cats often explicitly call for a very short muzzle and a vertical face plane with minimal muzzle protrusion — instructions that produce similar skull shapes across species. As Drake noted in the study release, the language used for breeds such as the Pekingese and the Persian is strikingly similar.

Welfare Concerns And Health Risks

While many people are drawn to infantile features, extreme modifications can harm animal welfare. Flat‑faced (brachycephalic) breeds such as pugs, French bulldogs and Persian cats commonly suffer from breathing difficulties, overheating, eye injuries, dental crowding and an increased need for surgical interventions. These health problems are a direct consequence of selecting for extreme facial shapes rather than natural evolution.

Outcrossing — mating with less related or mixed‑breed animals — can reduce the prevalence of inherited problems linked to extreme traits. Although some owners may resist mixed litters for aesthetic or status reasons, responsible breeding that prioritizes health can mitigate many of the issues the study highlights.

What This Study Means

The research underscores a broader tension between human aesthetics and animal welfare. As breeders and pet owners continue to value infant‑like traits, it is important to weigh those preferences against the real health costs they impose on companion animals. The study offers both a cautionary tale and an opportunity: recognizing how our choices shape animals’ bodies opens the door to more humane breeding practices.