Mary Allen
Dogs have faster facial expressions than wolves – this has now been anatomically proven. People prefer animals whose facial expressions are as quick as their own.
Soaking wet dogs, dogs happily snapping at treats, dogs blinking at the camera underwater, or characterful portraits of individual dog personalities: calendars and illustrated books that show the face of man’s four-legged “best friend” in a wide variety of situations are reliable sales successes. Behind people’s fascination with dog faces is probably the unique communication between the two species. The fact that people and dogs often look each other in the face and communicate using facial expressions distinguishes their relationship from that between humans and other pets.
Nimble fibers predominate
The importance of canine facial expressions and their emergence during domestication has meanwhile been the subject of various studies. Anne Burrows and Kailey Olmstead from Duquesne University in Pennsylvania are now adding a new piece to the puzzle. Biologist and anthropologist Burrows and animal physiologist Omstead compared the proportion of slow (“slow-twitch”, Type I) and fast (“fast-twitch”, Type II) muscle fibers in two facial muscles of dogs, wolves, and humans. Immunohistochemical analysis of samples from the orbicularis oris muscle and the zygomaticus major muscle – both muscles of the mouth – revealed that the fast “fast-twitch” fibers in the muscles in dogs account for 66 to 95 percent, while the proportion in their ancestors, the wolves, only reached an average of 25 percent.
The muscle fiber composition in the dog’s face is thus similar to the composition of human facial muscles. Burrows and Olmstead conclude that during the domestication process, humans consciously or unconsciously preferred individuals with fast facial expressions.
Anatomy of the “dog look”
However, the wolf ancestors already had some prerequisites for nimble facial expressions that other animal species do not have – this was shown by a team led by Burrows in 2020 in the specialist magazine “The Anatomical Record”. In contrast to cats, dogs, and wolves, therefore, have a very pronounced layer of connective tissue between the facial muscles and the skin. Humans also have a fiber layer, known as the SMAS (superficial musculoaponeurotic system). In addition to the actual mimic muscles, it is considered a decisive factor for the high mobility of the human face and could accordingly also contribute to mimic flexibility in dogs.
A publication in the Proceedings of the National Academy of Sciences, in which a group around Burrows described in 2019 that dogs have stronger muscles for raising the medial part of the eyebrow than wolves, generated intensive media coverage. This creates the typical “dog look” that triggers caring behavior in humans.
Frequently Asked Question
What does the dog look mean?
Evolutionary experts speak of the selection pressure that created the typical dog look: People probably took care of dogs that had the heart-rending look more often and more intensively, so they were preferred. And so the eyebrow muscle caught on as a survival advantage.
Where does the dog look come from?
The researchers suspect that these developed into domestic dogs in the course of the taming of wolves. The typical dog look makes the animals look childish. Also, they resemble a sad person, which triggers the protective instinct in humans.
Why do dogs have eyebrows?
Eyebrows are an important means of communication and dogs have internalized that. We, humans, communicate with dogs a lot through looks. When a dog is at a loss, it looks a person in the eye, at the top of the eye to be precise.
How does the dog see?
Dogs see colors in the blue-violet and yellow-green ranges. So they lack the perception of the red color spectrum – comparable to a red-green-blind person. Many fish and birds, but also other animals, even have four types of cones, so they see more colors than we do!
Does the dog have a sense of time?
An essential factor that gives dogs a framework for their sense of time is their biorhythm. Like most mammals, dogs live according to a circadian rhythm: their bodies tell them when they can be active and when they need to rest for about 24 hours.
Why does my dog look so sad?
Some dogs exhibit behaviors that indicate they are feeling grief when a loved one dies or is no longer there. Dogs are very receptive to human body language and moods and can embrace our sadness after the loss of someone special.
Can a dog cry properly?
Dogs cannot cry for sadness or joy. But they can also shed tears. Dogs, like humans, have tear ducts that keep the eye moist. The excess fluid is transported through the ducts into the nasal cavity.
Can a dog laugh?
When dogs show teeth, many people still think that this is always a threatening gesture. But what many dog owners have long believed is now also confirmed by research: dogs can laugh.