Humans adore dogs with soulful brown eyes, whereas their wild cousins, wolves, frequently have piercing yellow eyes. According to a new study, this eye-dye preference may be rooted in our shared evolutionary history. Wolves evolved into friendly pups over time, shedding their wild ways for couch cuddles. This shift resulted in changes in appearance, including changes in eye color. The bright yellow eyes of wolves, which were once necessary for hunting in low light, became less important for domesticated dogs. Meanwhile, darker eye colors appeared, possibly attracting human affection. According to the study, which was published in Royal Society Open Science, human preference for puppy-dog eyes may have unintentionally influenced canine evolution.
Dogs with dark eyes may have evolved the trait largely as a means to send non-threatening gaze signals to humans
Akitsugu Konno, a behavioral scientist at Teikyo University of Science, and his team conducted a study to investigate the rationale behind this evolutionary phenomenon, according to a press release. They altered photos of dogs representing 33 different breeds, ranging from corgis to Irish wolfhounds, to make the eyes lighter or darker. Following that, the researchers showed the edited images to a group of 142 Japanese volunteers, the majority of whom were students. The participants were tasked with rating each dog on various characteristics such as friendliness, aggression, maturity, and intelligence.
According to the findings, volunteers perceived dogs with dark eyes as social and non-aggressive, giving them lower intelligence and maturity ratings while associating them with puppy-like characteristics.
“I speculate that lighter irises have some evolutionary advantage for wolves, but domestication has lost this selective pressure and darker eyes have emerged in some primitive dogs,” Akitsugu Konno, the first author of the research from Teikyo University of Science, told The Guardian.
“We speculate that a darker iris makes it more difficult to distinguish the size of the pupil and thus gives the illusion of a large pupil, which is associated with our perception of being more infant-like,” Akitsugu said.
“Overall, dogs with dark eyes may have evolved the trait largely as a means to send non-threatening gaze signals to humans,” the team writes