Breeding for Cuteness Made Some Dogs and Cats Evolutionary Look-Alikes
Researchers analyzed 1,800 skulls and found that “baby-faced” breeds have converged evolutionarily, but at the cost of our beloved pets’ health.
By Sarah Simon
Monday, June 15, 2026
Nancy Wong, CC BY-SA 4.0, via Wikimedia Commons
EARTH, Laniakea Supercluster—Big eyes, a button nose, and a sweet little round head. Humans find these “baby-face” features so endearing that we’ve bred our pets (namely, our cats and dogs) to have them.
Pugs and Persian cats? We go goo goo ga ga for them.
But researchers now say our involvement in their evolution has done something stranger than we realized. In work published in the Proceedings of the National Academy of Sciences (PNAS) last year, a team led by Washington University evolutionary biologist Jonathan Losos 3D shape-analyzed upwards of 1,800 skulls.
They aimed to assess the evolution of skull shapes in domestic cats (Felis catus) and domestic dogs (Canis familiaris), as compared to wildcats (Felis silvestris) and wolves (Canis lupus)––living ancestors of our domesticated darlings. Surprisingly, they found baby-face cats and dogs to be more similar to each other than to those very same living ancestors.
“Who would have thought that you could substantially erase differences accumulated over 50 million years, just by selecting for those characteristics?” Losos remarked in a press release.
Originally, researchers were curious to see whether cats showed as much within-species variation as dogs do. What they ended up finding was both a resounding yes, along with their main discovery.
“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,” added Losos. “I don’t think anyone would have expected that.”
Losos and his colleagues already study “convergent evolution,” or how similar environmental pressures drive adaptation across species. For example, different flying species, from pterodactyls to bats, evolved to take flight due to similar natural selection pressures. But what this study shows is that this can also be done artificially—not through natural selection, but human selection.
While this finding is striking, and maybe even kind of cool, there’s a downside: The negative health effects of baby-faced breeding have been documented for decades. And with that, anyone with a pug might already be rolling their eyes, thinking about vet bills.
The smooshed-in snouts (which are required to attain that “button nose” charm) are well known to lead to breathing problems and other respiratory issues. Just have a pug play fetch the next time you can (you’ll hear that pant).
What’s more, the selection pressures that gave our pets baby faces aren’t exactly natural—just take a look at how breeders describe what they’re looking for.
The American Kennel Club described their standards for Pekingese dogs: “The topskull is massive … When viewed from the side, the chin, nose leather and brow all lie in one plane … A line drawn horizontally over the top of the nose intersects slightly above the center of the eyes.”
In this case, then, breeders’ selection pressures appear to worsen our pets’ health rather than help them survive and adapt to environment.
“There are all kinds of skull problems with these cats and dogs, because of the way they have been altered,” Losos said. “There are efforts by some groups led by veterinarians to outlaw breeding such extreme types…and we really need that, for the benefit of the animals.”
As long as baby-faced pets still exist, however, Losos and colleagues plan to extend their research across more breeds, as well as older ancestors, such as saber-toothed tigers.
Perhaps this research will continue to shed light on how natural selection helps animals adapt to their environment—rather than to aesthetic preferences, no matter how much we coo over them.
About Sarah Simon
Almost psychologist, interested in humanity's cosm as micro of the macro. Constantly connecting the dots.
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