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An atypical museum assortment in Bern, Switzerland, contains the most extensive scientific compilation of purebred dogs globally, featuring 2,800 skulls from over 100 breeds. Long ago, a scientist from Cornell University, Abby Grace Drake, analyzed many of these skulls to examine the variety among dogs and contrast it with wild members of the canine family. Her findings revealed that dog breeds exhibit a far greater diversity in skull morphology compared to wild canines like wolves, foxes, and coyotes.
WashU evolutionary biologist Jonathan Losos appreciated the paper and, as his focus shifted to felines, he questioned whether cat breeds exhibited a similar level of diversity when compared to their wild counterparts.
In a recent investigation published in PNAS during the week of April 28, Losos and Drake unveiled their astonishing discoveries pertaining to our two most cherished companion animals.
Similar to dogs, cat breeds differed more from one another than wild felines like tigers, lions, and ocelots do. However, another revelation was entirely unforeseen.
“The initial plan was to correlate the cat morphology onto the same graph used for dogs and evaluate how varied the cats were,” Drake recounted. “We didn’t anticipate witnessing what we found, which was that the cat shape space overlapped with the dog shape space. When I observed that, I thought, ‘What’s happening? That’s incredible.’”
It appears that humans have molded certain cats and dogs into strikingly similar forms. The biologists documented proof of a type of “copycat” evolution between extremely brachycephalic breeds of cats and dogs. Decades of deliberate breeding have resulted in these animals converging on a round, flat-nosed cranial shape favored by humans — even though this form often leads to various health issues.
“The skulls of a Pug or a Pekingese and a Persian cat share more resemblances than either does to their ancestors, the wolf and the North African wildcat,” stated Losos, the William H. Danforth Distinguished University Professor in Arts & Sciences at Washington University in St. Louis. “I doubt anyone would have predicted that.”
“The canid and felid families diverged evolutionarily 50 million years ago. Considering the appearances of canids and felids in nature, they seem quite distinct,” Losos noted. “Currently, what’s occurring is that breeders are choosing for comparable juvenile traits in both dogs and cats: prominent eyes, diminutive noses, and round heads. Who would have assumed that it was possible to significantly diminish differences accumulated over 50 million years merely through selecting for those traits?”
Losos probably should not have been astonished. Much of his lifelong research has concentrated on how species subjected to similar natural selection pressures evolve analogous features as adaptations.
This phenomenon of “convergent evolution” elucidates how birds, bats, and pterosaurs — unrelated species — developed comparable modes of flight. In pursuit of the advantages that flight provides, these creatures “converged” on similar methods of wing development. This new research reveals that a different form of selection — artificial selection influenced by human decisions — can also lead to convergent evolution.
Humans have influenced dogs and cats to take on a juvenile shape because breeders of both species have been choosing for the same characteristics in their breed standards, Losos and Drake asserted.
“If you examine the breed standards for the Pekingese and the Persian, the terminology is quite alike concerning the desired placement of the nose between the eyes and the face maintaining a vertical plane without muzzle protrusion,” Drake explained. “They established these breed standards and successfully achieved them.”
What Breeders Desire
Current breed standards for extreme juvenile-faced breeds of dogs and cats are strikingly similar. For instance:
The Cat Fanciers’ Association standard for Persian cats specifies: “Head … round and substantial … When seen in profile, the prominence of the eyes is noticeable, and the forehead, nose, and chin appear to be vertically aligned … Nose … situated centrally between the eyes.”
The American Kennel Club standard for Pekingese dogs states: “The topskull is substantial … When viewed from the side, the chin, nose bridge, and brow align in a single plane … A horizontal line drawn across the top of the nose intersects just above the center of the eyes.
Losos, who co-directs the Living Earth Collaborative at WashU, stands as a repeatedly recognized expert in the domain of evolutionary biology. Researchers in his laboratory mainly focus on the behavioral and evolutionary ecology of lizards. Recently, Losos has shifted his focus to felines and authored a popular science book,
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“The Cat’s Meow: How Cats Evolved from the Savanna to Your Sofa,” and he conducts an upper-level course on the biology of household cats.
Drake serves as a senior instructor in the ecology and evolutionary biology department at Cornell. The group also comprised researchers from seven additional institutions both nationally and internationally.
Losos and Drake employed 3D shape assessments to investigate convergence and divergence in the evolution of cranial structures in domestic cats (Felis catus) and domestic dogs (Canis familiaris). They scrutinized a total of 47 3D reference points across 1,810 skulls from dogs, cats, the wildcat (Felis silvestris) and wolf (Canis lupus) ancestors of the two domesticated species, as well as other extant members of the feline and canine families.
While the researchers had abundant resources for canine skull data, they were missing a similar museum collection of feline specimens. Thus, the team sought a broader data source: digital CT scans of living cats, obtained as part of contemporary veterinary care. Losos reached out to veterinary clinics and other establishments to request their scans, from which Drake extracted measurements for comparison with the existing canine data.
Losos and Drake also revisited the evolutionary background of the short-faced dog and cat breeds, respectively. They discovered that some of the most identifiable examples of today’s baby-faced fads are not actually interconnected.
“We realized that the Asian short-faced dogs such as the Pekingese and Pugs have no real relation to bulldogs — or the English short-faced breeds,” stated Drake. “This short-faced characteristic has evolved twice among dogs, and also twice among cats, emerging in the Persians and the Burmese. Therefore, we are witnessing not only convergence between the two species — cats and dogs — but also convergence within each species.”
Losos and Drake emphasize that they do not endorse the human inclination toward short, flat faces in cats and dogs. The artificial selection for baby-faced animals has led to significant health complications that have been thoroughly documented, according to the scientists.
“Some groups led by veterinarians are working to prohibit the breeding of such extreme types,” remarked Losos. “And we definitely need that, for the welfare of the animals. There are numerous skull issues with these cats and dogs, due to the alterations they have undergone.”
The team aspires to expand their research by gathering additional data on modern dogs and cats, while also exploring the wide range of extinct species — for instance, saber-toothed cats or the dire wolf.
Lastly, Losos pointed out that the findings from this research may likely underestimate the variety of skull shapes among cat breeds since the researchers did not consider any instances of contemporary Siamese cats (whose faces have recently become notably long and angular) or other breeds with distinctive head shapes, like Havana Browns, Cornish Rex, or Savannahs. “We hope to acquire CT scans of such individuals in the future as we advance our studies,” he stated.
Drake AG, Revell LJ, Klingenberg CP, Lattimer JC, Nelson NC, Schmidt MJ, Zwingenberger AL, Moyer JK, Losos JB. Copy-Cat Evolution: Divergence and Convergence Within and Between Cat Dog Breeds. PNAS, Apr. 2025. https://doi.org/10.1073/pnas.2413780122
The article Copycat evolution was originally featured on The Source.
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