The domestication of dogs changed the color of their eyes, which with evolution became a friendlier and less threatening brown shade to humans, far from the lighter eyes of their wolf cousin.
“The color of the irises of dogs is darker than that of wolves and this darker color positively influences people’s perception of dogs,” according to a study by scientists from the animal sciences department of Japan’s Teikyo University.
The work, published on Wednesday in the scientific journal Royal Society Open Science, believes that humans naturally selected dark-eyed dogs, with selective pressure favoring animals whose eyes were “perceived by humans as friendly and youthful.”
The domestication of the dog, from the gray wolf, occurred gradually over a period between 50,000 and 15,000 years ago.
This Wednesday, most of the canines associated with wolves have eyes with a light iris, tending to yellow, with the dark pupil in the center conspicuous.
On the contrary, The eyes of dogs from about three dozen breeds selected for the study have large, dark, brownish irises, making it difficult to distinguish the pupil.
This difference will be of great importance in the exchange of views between man and his “faithful companion”. This exchange, which the dog knows how to use to attract the owner’s attention, leads to the production of oxytocin, in a similar way to what happens during the exchange of glances between mother and child.
Teikyo researchers based their findings on studies in primates, particularly humans, where a dilated pupil, for example, is associated with more positive emotions than a constricted pupil.
A large iris is also unconsciously associated with that of a youthful being and therefore more vulnerable and harmless.
According to the study, a dog with a darker eye color is seen “as vulnerable and in need of protection.”
However, scientists admit that there are limits to their research, such as that of ‘familiarity’, i.e. the possibility that people prefer dogs with dark eyes simply because they are the most numerous, or the fact that the tests carried out have a limited number of dog species in relation to all existing species.
“It is the first study on the difference in eye color between dogs and wolves,” the lead author, Akitsugu Konno, told Agence France-Press.
Considering that “factors other than human preference may contribute to many dogs having darker eyes,” the researcher added that he hopes other studies on the subject can “confirm the universality of the phenomenon.”
Source: DN
