Those irresistible puppy dog eyes are the result of evolution, scientists explain

Puppy dog eyes.

They’re so stinkin’ cute, and according to a recent study from researchers at the University of Portsmouth, dogs developed the ability to make that sad, innocent look in order to better communicate with humans.

For the study, researchers compared the anatomy and behavior of dogs and wolves and discovered that while the arrangement of their facial muscles was similar, there was a portion above their eyes that was different.

Dogs, which were domesticated from wolves about 33,000 years ago, have a small muscle that allows them to “intensely” raise their eyebrow.

Dr. Juliane Kaminski, who led the research, called the evidence “compelling” that dogs did in fact develop a muscle to raise their eyebrow.


In addition to studying dogs’ and wolves’ anatomy, they studied the animals’ behavior.

The research, which was published in Proceedings of the National Academy of Sciences (PNAS), found that when exposed to a human for two minutes a dog raised their inner eyebrow “more and at higher intensities than 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.”


In order for researchers to determine if puppy dog eyes are the result of evolution they compared the facial anatomy and behavior of dogs and wolves and learned that the muscle that allows dogs to lift their eyebrow is “a scant, irregular cluster of fibers” in wolves.

“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,” Lead anatomist and co-author of the paper, Professor Anne Burrows said.


Researchers are astounded how the muscle, which is so thin it’s see-through, has evolved in such a short period of time and has had such impact on the human-dog relationship.

“It is really remarkable that these simple differences in facial expression may have helped define the relationship between early dogs and humans,” co-author and anatomist Adam Hartstone-Rose said.

Can you believe that?

Dogs have evolved over time to better communicate with humans and the result is those puppy dog eyes that are so hard to ignore.

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