This explains everything.

By Meghan Overdeep
June 19, 2019

Anybody who has ever been on the receiving end of a pair of puppy dog eyes knows they're capable of melting hearts from miles away. And according to a new study, that's no accident.

Experts in the UK and USA found a difference in the musculature of the faces of domesticated dog faces that allows them to "better communicate with humans."

Their findings, published in the Proceedings of the National Academy of Sciences found that dogs' faces can make complex expressions that wolves' can't, thanks to a special pair of muscles—the RAOL and LAOM—framing their eyes.

That's right: dogs have evolved to more effectively pull on our heartstrings.

A dissection of dog and wolf heads found that the facial muscle anatomy of both animals was nearly identical, save for eyebrow muscles, found only in dogs, that enable them to raise their eyebrows. Moving these muscles, researchers wrote, makes dogs' eyes "appear larger, more infant like, and also resembles a movement humans produce when they are sad."

Juliane Kaminski, a comparative psychologist at the University of Portsmouth in the UK and the study's first author, told CNN that this prompts a "nurturing" response in humans.

"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," Kaminski explained.

Experts believe that the facial change has occurred over thousands of years of domestication.

"The raised inner eyebrow movement in dogs is driven by a muscle which doesn't consistently exist in their closest living relative, the wolf," lead anatomist Anne Burrows of Duquesne University, another of the paper's co-authors, said in a statement. "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."

Give them another 33,000 and we have no doubt that dogs will be running the whole show.