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Dogs Might Have Developed ‘Puppy Dog Eyes’ Just to Make Humans Melt

New research suggests that dogs’ facial anatomy has changed over thousands of years specifically to allow better communication with us.

The dynamic duo of dogs and humans goes back more than 33,000 years to when dogs were first domesticated. And it’s proven to be a remarkable interspecies relationship. Through selection during domestication, dogs have developed behavioral adaptations that have led to a unique ability to read and use human communication in ways that other animals cannot.

“Dogs are more skillful in using human communicative cues, like pointing gestures or gaze direction, even than human’s closest living relative, chimpanzees, and also than their own closest living relatives, wolves, or other domesticated species,” write the authors of a new study looking at the evolution of puppy dog eyes, of all things.

But as innocent (or devious) as they may seem, there is a lot to learn about the big-eyed gazes that humankind’s best friend has mastered so well.

“We hypothesize that dogs with expressive eyebrows had a selection advantage and that ‘puppy dog eyes’ are the result of selection based on humans’ preferences,” notes the study.

The research comprises the first detailed analysis looking at the differences in anatomy and behavior between dogs and wolves. They concluded that the facial musculature of both species were similar, except above the eyes: “Dogs have a small muscle, which allows them to intensely raise their inner eyebrow, which wolves do not.”

Or as the University of Portsmouth puts it, “Dogs have evolved new muscles around the eyes to better communicate with humans.”

dog and wolf
Facial musculature in the wolf (C. lupus) and dog (C. familiaris) with differences in anatomy highlighted in red. Image courtesy of Tim D. Smith (Cambridge University Press, Cambridge, UK)/CC BY 4.0

The authors suggest that this special puppy-dog-eye ability basically makes humans melt into a puddle. Ok, not exactly their words. But they do suggest that the look triggers a nurturing response in humans because it makes the dogs’ eyes “appear larger, more infant like and also resembles a movement humans produce when they are sad.”

(It’s almost like they have been taking lessons from the big, irresistible eyes of giant pandas.)

Further backing up the hypothesis is another recent study showing that dogs seem to produce significantly more AU101 [inner eyebrow raise] when a human is looking at them.

“The evidence is compelling that dogs developed a muscle to raise the inner eyebrow after they were domesticated from wolves,” said leader of the current study, Dr. Juliane Kaminski, a comparative psychologist at the University of Portsmouth, Kaminski.

“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,” she add. “This would give dogs, that move their eyebrows more, a selection advantage over others and reinforce the ‘puppy dog eyes’ trait for future generations.”

Co-author Anne Burrows, an anatomist from Duquesne University, Pittsburgh, says that this anatomical difference between the wolves and dogs occurred relatively quickly. “This is a striking difference for species separated only 33,000 years ago and we think that the remarkably fast facial muscular changes can be directly linked to dogs’ enhanced social interaction with humans.”

With which co-author Rui Diogo agreed: “I must admit that I was surprised to see the results myself because the gross anatomy of muscles is normally very slow to change in evolution, and this happened very fast indeed, in just some dozens of thousands of years.”

In concluding that “domestication transformed the facial muscle anatomy of dogs specifically for facial communication with humans” in a mere 33,000 years, the study leaves much for the dog lovers amongst us to wonder. What evolutionary changes might this unique partnership bring about in another 33,000 years? And can we please have talking dogs someday?

The whole study (and video clips of wolves versus dogs!) can be seen at the Proceedings of the National Academy of Sciences (PNAS).

Source: Tree Hugger