New research comparing the anatomy and behavior of dogs and wolves suggests that the facial anatomy of dogs has changed over thousands of years specifically to allow them to better communicate with humans.
In the first detailed analysis that compared the anatomy and behavior of dogs and wolves, the researchers found that the facial musculature of both species was similar, except above the eyes. Dogs have a small muscle, which allows them to intensely lift the inner part of the eyebrow, which wolves do not.
Authors from the University of Portsmouth suggest that the internal movement of raising the eyebrows triggers an affectionate response in humans because it makes dogs’ eyes appear larger, more childlike, and also resembles a movement that humans produce when they are sad.
The research team, led by comparative psychologist Dr. Juliane Kaminski from the University of Portsmouth, included a team of behavioral and anatomy experts from the United Kingdom and the United States.
Dr Kaminski said: “The evidence is compelling that dogs developed a muscle to raise the inner brow of the eyebrow after they were domesticated by wolves.
“We also studied the behavior of dogs and wolves, and when exposed to a human for two minutes, dogs raise the inside of their eyebrows more and with greater intensity than wolves.
“The findings suggest that expressive eyebrows in dogs may be the result of unconscious human preferences that influenced selection during domestication. When dogs make the move, it seems to elicit a strong desire in humans to care for them. This would give brow-wagging dogs more of a selection advantage over others and would reinforce the ‘puppy-eye’ trait for future generations. “
Previous research by Dr. Kaminski showed that dogs moved their eyebrows significantly more when humans were looking at them compared to when they were not looking at them.
She said: “The AU101 movement is significant in the human-dog bond because it could elicit an affectionate response from humans, but it could also create the illusion of human-like communication.”
Lead anatomist Professor Anne Burrows of Duquesne University in Pittsburgh, a co-author of the paper, said: “To determine whether this brow movement is the result of evolution, we compared the facial anatomy and behavior of these two species and we found the muscle that allows the increase of eyebrows in dogs was, in wolves, a group of scarce and irregular fibers.
“The raised internal brow movement in dogs is driven by a muscle that does not exist consistently in their closest living relative, the wolf.
“This is a striking difference for species separated only 33,000 years ago and we believe that the remarkably rapid facial muscle changes may be directly related to the improved social interaction of dogs with humans.”
The findings show how important faces can be in capturing our attention and how powerful facial expression can be in social interaction.
Co-author and anatomist Adam Hartstone-Rose of North Carolina State University said: “These muscles are so thin that you can literally see right through them, and yet the movement they allow seems to have such a powerful effect that It seems they have been under substantial evolutionary pressure.
“It’s really remarkable that these simple differences in facial expression may have helped define the relationship between early dogs and humans.”
The only species of dog in the study, published in the journal. procedures of the National Academy of Sciences (PNAS): The one without the muscle was the Siberian husky, which is among the oldest dog breeds.
An alternative reason for the human-dog bond could be that humans have a preference for other individuals who have whites in their eyes and that the intense movements of AU 101 expose the whites of dogs’ eyes.
It is not known why or exactly when humans first brought wolves from the cold and evolution from wolf to dog began, but this research helps us understand some of the possible mechanisms underlying dog domestication.
Source: University of Portsmouth
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