THE EVOLUTION OF PUPPY DOG EYES
New research has shown that dogs have evolved muscles around their eyes, which allow them to make expressions that prompt a nurturing response in humans. “Puppy dog eyes” helped domesticated dogs bond with their humans.
New research comparing the anatomy and behavior of dogs and wolves suggests dogs' facial anatomy has changed over thousands of years specifically to allow them to better communicate with humans.
In the first detailed analysis comparing the anatomy and behavior of dogs and wolves, 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 raise their inner eyebrow, which wolves do not. This is an effective movement for dogs because it makes the dogs' eyes appear larger, more childlike and also resembles a movement humans produce when they are sad. Humans likely would have an "unconscious preference" to protect and breed from dogs with such an appealing trait, giving them an evolutionary advantage and reinforcing this change in subsequent generations.
The research team, led by comparative psychologist Dr. Juliane Kaminski, at the University of Portsmouth, included a team of behavioral and anatomical experts in the UK and USA.
Dr. Kaminski said: "The evidence is compelling that dogs developed a muscle to raise the inner eyebrow after they were domesticated from wolves. 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."
Dr. Kaminski's previous research showed dogs moved their eyebrows significantly more when humans were looking at them compared to when they were not looking at them. This suggests that dogs use this behavior deliberately, although she does not believe dogs intentionally manipulate their humans. I, for one, might disagree with that! My dog knows how to get treats for sure!
Other parts of the study included behavior testing of dogs and wolves when interacting with humans, and they found that dogs used this behavior regularly and wolves did not.
In an earlier study, Kaminski found that the more dogs pulled the woeful expression, the faster they were adopted from shelters. In that respect, puppy dog eyes proved a more endearing quality to humans than tail wagging or lolling tongues. The sad, pleading look tugs at people’s heartstrings.
There's still a lot to learn about the many ways in which domestication changed wolves as they became dogs, and who would have thought that humans could have played a significant role in the evolution of a single, unique muscle that is used in dog-human social exchanges? It is not known why or precisely when humans first brought wolves in from the cold and the evolution from wolf to dog began, but this research helps us understand some of the likely mechanisms underlying our dogs’ domestication.
If you would like to learn more about this study entitled “Evolution of facial muscle anatomy in dogs” in the Proceedings of the National Academy of Science, find it here https://www.pnas.org/content/116/29/14677.
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