Recent research centers on anatomy and behavior of dogs and wolves. According to the study facial anatomy of dogs has evolved over the years which allows them to communicate better with humans.
The team of researchers observed that both wolves and dogs have similar anatomy, except the facial musculature above the eyes. Dogs have developed new muscles around the eyes, which allegedly makes them communicate more efficiently with humans. The study suggests that dogs have a small muscle due to which they can intensely raise their inner eyebrow, which the wolves are not capable of. The raising of the eyebrows makes the dog’s eyes appear large, and infant-like. According to the authors of the study, this feature stimulates an affectionate response among humans, since the eyebrow rising movement resembles an action which humans make when they are sad. This is allegedly also one of the reasons why humans chose dogs for domestication over wolves.
“The evidence is compelling that dogs developed a muscle to raise the inner eyebrow after they were domesticated from wolves. We also studied dogs’ and wolves’ behavior, and when exposed to a human for two minutes, dogs raised their inner eyebrows more and at higher intensities than wolves,” says Dr. Juliane Kaminski, a comparative psychologist at the University of Portsmouth.
“The findings suggest that expressive eyebrows in dogs may be a result of humans unconscious preferences that influenced selection during domestication. When dogs make the movement, it seems to elicit a strong desire in humans to look after them. This would give dogs, that move their eyebrows more, a selection advantage over others and reinforce the ‘puppy dog eyes’ trait for future generations,” Kaminski adds.
Moreover, Kaminski suggests that dogs raised their eyebrows more when humans were looking at them. This further intensifies the human-dog bond, because it creates an illusion of human-like communication.
This movement of the eyebrows does not exist in the dog’s closest relative, the wolf. This action of raising an inner eyebrow is named as Action Unit (AU) 101. According to Co-author and anatomist Adam Hartstone-Rose, at North Carolina State University, the muscles responsible for the movement are very thin, and yet their effect is very powerful.
The team adds that the discovery in the gross anatomy of muscles was surprising since muscles change slowly through evolution. Moreover, soft tissues, along with muscles don’t survive the fossil record. However, AU101 has happened rapidly within some dozens of thousands of years. The only dog species in which AU101 is absent is Siberian husky, belonging to an ancient dog breed.
The research study was published in the journal Proceedings of the National Academy of Sciences of the United States of America (PNAS) and draws attention to the role, faces and facial expressions play to capture attention and in social interactions. Moreover, it has also highlighted the human-dog bond, where humans prefer individuals with whites in their eyes, and AU 101 exposes the white part in a dog’s eye. The study also helps to understand the mechanisms of dog domestication