You know that look. Those big, shiny eyes fixed on you from under the dinner table. The wet nose wiggling, and the eyebrows and ears moving up down to the movement of your fork. “Please, can I have some food?” You relent, and toss some food on the floor. Mission accomplished!

Most dog owners are very familiar and susceptible to their pet’s “puppy dog eyes” trick. But did you know that this phenomenon isn’t just limited to your own spoiled pooch? In fact, it is a result of thousands of years of canine evolution!

On Monday, researchers at the University of Portsmouth in the UK and Duquesne University in Pittsburgh published their study on “Evolution of facial muscle anatomy in dogs,” in the journal Proceedings of the National Academy of Sciences of the United States of America (PNAS). The team examined the facial structures of wolves and domesticated dogs, as well as observing the behavior of live wolves and dogs when in contact with humans. They concluded that dogs likely developed facial muscles around their eyes in order to appeal to humans.

The study, lead by Dr. Juliane Kaminski in the UK and Professor Anne Burrows in the US, focused on a region of muscle they called Action Unit 101. They found that dogs had more muscle fibers in this area than wolves, giving them the ability to move their eyebrows in ways that wolves cannot.

“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,” says Professor Burrows. According to Dr. Kaminski, “the AU101 movement is significant in the human-dog bond because it might elicit a caring response from humans but also might create the illusion of human-like communication.”

Overall, they conclude that “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.”

So next time your friend laments her inability to resist those “puppy dog eyes,” let her know she’s not alone – and that dogs have been perfecting that look on humans like her for thousands of years!

Want an example of “puppy dog eyes” in action? Check out this fun “silent film” starring our DogWatch Office Dog Biz!

Our featured dog is Darby the Cavachon (Cavalier King Charles Spaniel and Bichon Frise mix) from DogWatch Hidden Fence of North Alabama