Or as the University of Portsmouth puts it, "Dogs have evolved new muscles around the eyes to better communicate with humans".
Researchers dissected dog and wolf heads and found that the facial muscle anatomy of both animals was nearly identical - except for an eyebrow muscle, found only in dogs, that allows them to "intensely" raise their eyebrows.
Such a stark diversion in what in evolutionary terms is a short period of time has led the researchers to believe that humans naturally favour canines able to look at them with big "puppy dog" eyes, giving them a selection advantage.
"The findings suggest that expressive eyebrows in dogs may be a result of human unconscious preferences that influenced selection during domestication, "said behavioural psychologist Juliane Kaminski of the University of Portsmouth".
Dogs that move their eyebrows more would thus have a "selection advantage over others and reinforce the "puppy dog eyes" trait for future generations".
"These muscles are so thin that you can literally see through them - and yet the movement that they allow seems to have such a powerful effect that it appears to have been under substantial evolutionary pressure", said co-author Dr. Adam Hartstone-Rose, an anatomist at North Carolina State University.
The dynamic duo of dogs and humans goes back more than 33,000 years to when dogs were first domesticated.
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The researchers also studied the behavior of dogs and wolves and found that when exposed to a person for intervals of two minutes, dogs raised their inner eyebrows more and at higher intensities than wolves.
The team of researchers came to this conclusion after studying the behavior of nine wolves, from New Forest Wildlife Park in the United Kingdom and Tierpark Petersberg in Germany, and 27 domesticated dogs from various shelters within the UK.
Dogs and wolves are different in a range of ways.
Researchers noted that it's also possible that humans have a preference for individuals that show the whites in their eyes and that the muscle exposes more of the white part of the dogs' eyes.
Though the dog and its ancestor have clear physical differences in "body shape and skeletal anatomy", the study stresses that the facial muscle finding is important because it deals with soft tissues, which "are inherently hard to document given that soft tissues do not readily fossilize".
But to be more convinced, he said, he would want to see results from a larger sample that included more dog breeds and wolf subspecies, as well as wolves and dogs with varying levels of experience with humans. "It could also mimic the facial movement humans make when they're sad", which helps highlight the importance of facial expressions in dog-human communication.
Burrows said she planned follow-up studies to examine more breeds.