Brow Wow Wow Yippe Yo Yippe Yay: Dogs Use Specialized Eye Muscles to Communicate with Humans

Evolution of facial muscle anatomy in dogs. Juliane Kaminski, Bridget M. Waller, Rui Diogo, Adam Hartstone-Rose, Anne M. Burrows. Proceedings of the National Academy of Sciences Jul 2019, 116 (29) 14677-14681; DOI: 10.1073/pnas.1820653116

Since the beginning of canine domestication roughly 15,000 years ago, each breed has been genetically designed through selective breeding to be adorable in their own unique way. Take for instance the bulldog with its squatty body and droopy jowls. Picture the golden retriever with its lean build and long beautiful locks. And who could forget the chihuahua with its bulgy eyes and rat-like little body- so ugly it’s cute!

Cuteness is actively bred into dogs; however, a recent study conducted at the University of Portsmouth suggests humans might have inadvertently bred the ultimate weapon of curtness into man’s best friend. That’s right, today we are breaking down the evolution of puppy dog eyes.

Puppy Dog Eye Procedure

Turns out all pups possess a special genetic feature that make them even more irresistible: a muscle known as the levator anguli oculi medialis, or LAOM. With this knowledge, a team of scientists lead by Juliane Kaminski of the University of Portsmouth sought to discover how it became part of a pup’s genetic makeup.

A rendering of the facial musculature of domesticated dogs and wolves. Differences in musculature are highlighted in red. Source: https://www.pnas.org/content/116/29/14677

Kaminski and her colleagues analyzed the facial anatomy of various dog breeds and wolves by dissecting cadavers provided by taxidermists, museums, and wildlife organizations. (No animals were harmed for testing). As the researchers expected, all the domesticated dog breeds possessed LAOM. The wolf specimens lacked LAOM; however, they possessed a few weak muscle fibers where LAOM rests in their domesticated counterparts.

The team also conducted research on living dogs and wolves. One at a time, a dog or wolf was observed by a researcher for a two-minute period. During observations researchers recorded the frequency and intensity of eyebrow movement. The researchers found both dogs and wolves displayed some eyebrow movement; however, only dogs could achieve high intensity eyebrow arching.

Brows on Fleek

In recent years, thick manicured eyebrows have dominated the beauty scene. In the 90s, eyebrows plucked razor-thin were all the rage. Around 2,500 BC Egyptian men and women filled in their brows with black makeup to offset their heavily lined eyes. Roughly 130,000 years ago our Neanderthal brethren rocked unkept eyebrows on their pronounced brow ridges.

No matter when or how they were styled, eyebrows have always played a crucial role in nonverbal communication between humans. Kaminski’s study proves that eyebrow movement is an effective form of nonverbal communication between species that might  have inadvertently given dogs of the past a leg up in selective breeding.

                                                                                             

  How Does LAOM Work?

Girl and chihuahua. Source: https://www.maxpixel.net/Girl-Promotion-Puppy-Friendship-Eyes-Look-Dog-3829473

LAOM is small but strong collection of muscle fibers that allow dogs to intensely raise their inner eyebrow. This movement mimics the expression humans make when they are sad or worried.

Try it out for yourself. Go to a mirror. Think sad thoughts and frown. If you notice that the inner corner of your eyebrows arch upwards, then good news: you are either a human or a dog. Congrats!

Kaminski and colleagues believe a dog’s ability to mimic human facial expressions may trigger a nurturing response in their caretaker, thus giving the pooch an evolutionary advantage in selective breeding. The study proves humans actively or inadvertently favored dogs with the ability to enlarge their eyes giving them a baby-like appearance, forever changing the facial anatomy of domesticated canines.

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Laine Farber

Laine Farber

I am recent graduate of Louisiana State University. With a background in journalism and a love of science, I have a passion for making science stories easy to understand and enjoyable to read. I am currently working in the education department of an environmental non-profit based out of New Orleans and stepping into the highly competitive freelance journalism game. When I am not rewriting a textbook or chasing down a story, you can find me walking along the lakefront, painting or feeding dry corn to ducks. For more information follow me on Twitter at @lfarber14 or Instagram @lainefarber.

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