The domestic canine, descended from the wolf, eventually evolved into “man’s best friend.” New research from the University of Portsmouth shows that facial muscles evolved over thousands of years, allowing dogs to better communicate with humans using those big, round, heart-melting “puppy dog eyes.”
The study comparing dog and wolf anatomy and behavior, published in the journal Proceedings of the National Academy of Sciences, found dogs have developed small muscles that wolves lack, allowing them to raise their inner eyebrows. Study authors suggest this eyebrow-raising, dubbed the AU101 movement, triggers a nurturing response in humans.
University of Portsmouth evolutionary psychologist Professor Bridget Waller says, “This movement makes a dogs’ eyes appear larger, giving them a childlike appearance. It could also mimic the facial movement humans make when they’re sad.”
Lead researcher Dr. Juliane Kaminski, a comparative psychologist also at the University of Portsmouth, says, “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.”
The only dog species in the study that did not have the muscle was the Siberian husky, which is among the most ancient dog breeds. It is not known why or precisely when humans first brought wolves in from the cold and the evolution from wolf to dog began, but this research helps us understand some of the likely mechanisms underlying dog domestication.
Perhaps the easiest way to communicate with your pets, or to understand their communication with you, is through observing their body language. Without saying a word, dogs and cats express emotion — and indicate when to come closer and when it’s wise to back away, says Susan Breslow, former head of publications for the ASPCA. Here’s a list of behavioral clues to the most commonly accepted messages your pet may be trying to send you:
Happy
Dog: Tail wagging side-to-side or circles, relaxed mouth, appears to smile
Cat: Eyes closed, ears forward, tail up, fur flat, purring, kneading with front paws
Alert
Dog: Ears up or forward, upright posture, eyes wide
Cat: Eyes wide, ears forward
Excited
Dog: Ears up, tail high, weight on rear legs
Cat: Ears up, direct glance, tail up and waving
Friendly
Dog: Jumps up or offers toy
Cat: Slow blinks
Fearful
Dog: Ears flat, tail between legs, cowers
Cat: Tail tucked or high and fluffed, ears sideways, pupils widen
Aggressive, Angry
Dog: Hostile, tail high, teeth bared, may vocalize, intimidating posture, weight shifted forward
Cat: Ears flattened, pupils narrow, whiskers point forward, tail thrashes, back arches, fur stands up, claws extend
Dominant, Defensive
Dog: Standing tall, tilts the body forward, tail high, ears up, unblinking
Cat: Pupils shrink, tail twitches, growls, snarls, hisses, spits
Submissive
Dog: Tucks tail, avoids eye contact, cowers
Cat: Crouches, flattens ears, tail tucked
Playful
Dog: Bouncy, energetic, bowing, nuzzles or paws at you, tries to get you to chase, squints/blinks eyes
Cat: Ears slightly forward, tail curled upward
Trusting
Dog: Turns back or exposes belly, wants to please
Cat: Kneads you, cat kisses, rubs its face on you, exposes belly, eats out of your hand, brings you presents (usually dead), quivering tail
Nervous, grumpy, tense
Dog: Yawns, licks face, exposes teeth
Cat: Pupils narrow, tail upright, vibrates
Curious
Dog: Tilts head, raises one paw
Cat: Ears up, direct glance, the tip of tail flicking
Sources: Reader’s Digest, Alley Cat Allies, ASPCA, Hills Pets
