Researchers have traced the history of eye color evolution across the cat family to a shared ancestor that walked the Earth more than 30 million years ago. In a peer-reviewed report, the researchers outline their conclusions.
Today, both large and small cats show a spectrum of iris colors, with cheetahs commonly displaying golden eyes, snow leopards appearing blue, and leopards often showing green irises.
In the study, eye colors were cataloged across 52 feline taxa, documenting substantial diversity for comparison.
The team then worked to reconstruct what the ancestral eye colors might have looked like in the cat lineage.
Findings suggest the earliest pre-cat lineages, including the relatives closest to cats, carried only brown eyes. After the split in this lineage, gray eyes appeared alongside brown.
Experts propose a genetic mutation that lowered pigment content in the eye as a likely driver of this shift.
Eye color is influenced by melanin, the pigment that exists in two main forms: brown eumelanin and yellow pheomelanin.
Shifting from brown to gray would require a reduction in eumelanin, producing a brownish-gray tone that sits between brown and gray.
The gray stage opened the path for green, yellow, and blue eyes, linking the ancestral brown palette to newer hues.
Researchers found no clear relationship between eye color diversity and activity patterns, geographic distribution, or habitat, leaving the question of possible adaptive reasons for different eye colors.
Earlier studies have explored explanations for color variation in feline eyes, highlighting a mix of genetics and environmental factors.