Research suggests that humans may have played a role in the development of dogs’ eye color through the process of evolution.
Scientists propose that the desire for a welcoming expression may have influenced the development of dogs’ eye color.
Since the domestication of canines, which occurred sometime between 15,000 and 50,000 years ago, humans have intentionally or unintentionally chosen specific characteristics in their dogs.
Out of all the species, it seems that humans are drawn to the puppy-like facial features of dogs. Researchers have discovered that dogs have developed specific facial muscles that enable them to make a sad expression, which elicits a caring reaction from humans and thus gives these dogs an edge.
New findings indicate that humans may have had an impact on the eye color of dogs. Researchers in Japan conducted a study and discovered that domesticated dogs are more likely to have dark eyes compared to their wild counterparts. Furthermore, humans tend to view dogs with dark eyes as more approachable.
Akitsugu Konno, the lead researcher from Teikyo University of Science, suggests that lighter irises may have provided a survival advantage for wolves in the past. However, due to domestication, this selective pressure has been lost and darker eyes have become more prevalent in certain primitive dog breeds.
The researchers suggest that humans may have unconsciously preferred dogs with dark eyes during the domestication process from wolves to dogs.
Konno mentioned that the breeding of certain dog breeds may have played a role in their eye color. An example is the blue merle coat color found in shelties and border collies, which is often linked to blue eyes.
In a journal published by the Royal Society Open Science, the researchers discuss their analysis of 22 images of grey wolves with varying coat colors and geographical origins. They also examined 81 images of domestic dogs and found that these dogs typically had darker and redder irises.
The scientists produced 12 sets of pictures, where one picture in each set featured a pet dog with light-colored eyes and the other featured the same dog with dark-colored eyes. A subset of these sets was presented to 76 individuals who were tasked with evaluating the dogs based on personality traits and their desire to interact with or own the dog.
The researchers discovered that canines with dark-colored eyes were perceived as more amiable compared to those with lighter eyes, and were also seen as more laid-back, sociable, and reliant, while being viewed as less hostile, intelligent, and mature. This pattern was consistent when the study was replicated with an additional 66 individuals.
According to Konno, it is believed that having a darker iris can make it challenging to accurately perceive the size of one’s pupil. This can create the illusion of a larger pupil, which is commonly associated with a more youthful appearance.
The scientists also mention that the connection between dark eyes and immaturity may lead humans to feel a desire to safeguard and nurture these canines. However, the study did not find a direct correlation between eye color and participants’ inclination to engage with or keep the dog.
The researchers state that dogs with dark eyes may have developed the trait primarily to communicate a non-threatening gaze to humans.