In a surprising new study, researchers have found that domestic cats and dogs—despite being distinct species—have evolved nearly identical facial features due to human selective breeding. The findings, published in PNAS, reveal how human preferences for “baby-faced” traits pushed both species to develop short noses, flat faces, and rounded heads, overriding millions of years of evolutionary divergence.
Convergent Evolution Driven by Human Choice
Jonathan Losos of Washington University in St. Louis and Abby Grace Drake of Cornell University compared skull shapes of domestic pets to their wild ancestors—wolves, foxes, lions, and tigers—using 3D scans and museum collections. While wild canids and felids maintain consistent skull structures, domestic breeds like pugs, Pekingese, and Persian cats showed extreme “paedomorphic” (baby-like) traits.
“These features mimic human infants—big eyes, small noses, round heads,” Losos said. “Humans essentially ‘rewrote’ evolution by selecting for these traits across species.” The team found such features evolved independently multiple times: Pekingese and pugs developed flat faces separately from bulldogs, while Persian and Burmese cats followed different genetic paths to the same look.
Health Costs of Aesthetic Breeding
While the convergent evolution is fascinating, researchers warn of severe health issues in extreme breeds. Shortened skulls often cause breathing difficulties, dental deformities, and eye problems. “We support veterinary efforts to reduce breeding of animals with exaggerated features,” Drake noted. The study highlights a trade-off: human aesthetic preferences have prioritized appearance over animal welfare.
Future Research Directions
The team plans to expand their analysis to modern long-faced breeds like Siamese cats and extinct species like saber-toothed tigers, aiming to map evolutionary changes in skull morphology. “This shows how powerfully humans shape evolution—for better or worse,” Losos concluded. The findings add to growing calls for ethical breeding practices that balance aesthetics with animal health.
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