In a surprising new study, scientists have found that some cats and dogs have evolved to look unusually alike—despite being very different animals.
These similarities didn’t happen in nature, but because of the way humans have selectively bred pets to match certain looks.
Researchers Jonathan Losos of Washington University in St. Louis and Abby Grace Drake of Cornell University studied the skull shapes of both cats and dogs, comparing them to their wild ancestors and relatives.
They found that while wild dogs like wolves and foxes and wild cats like lions and tigers have stayed fairly consistent in shape, domestic pets have become much more varied.
Even more surprising, some of the most extreme-looking breeds of dogs and cats—like Pugs, Pekingese, and Persian cats—have developed nearly identical, baby-like features.
Using 3D scans and skull collections from museums and veterinary hospitals, the researchers discovered that short-nosed, flat-faced pets across both species had evolved those features through “copycat” or convergent evolution.
This happens when different species independently develop similar traits—in this case, because people bred them to have big eyes, small noses, and round heads that resemble human babies.
What’s remarkable is that cats and dogs split from a common ancestor about 50 million years ago. In nature, canines and felines look very different.
But human preferences have driven both to develop the same features, essentially undoing millions of years of evolutionary differences.
The researchers found that this baby-faced look evolved more than once within each species.
For example, among dogs, the Pekingese and Pug developed these features separately from Bulldogs. Among cats, the Persian and Burmese breeds followed separate paths to the same flat-faced appearance.
This shows that even within a species, different breeds were pushed in the same direction by human choices.
While the findings are fascinating, the researchers are also concerned. These extreme facial features often come with serious health problems, like breathing issues and dental deformities.
Losos and Drake support efforts by veterinarians to reduce or ban the breeding of animals with overly shortened skulls for the sake of their health and wellbeing.
The team hopes to expand their work by studying more modern cat breeds, including long-faced ones like the Siamese and other unusual types. They’re also interested in examining extinct animals, such as saber-toothed cats and dire wolves, to better understand how skull shapes have changed over time.
This study, published in the journal PNAS, shows how powerful human preferences can be in shaping the evolution of our beloved pets—and how it can sometimes come at a cost.
