Your dog is the bestest dog ever. You know it. You’ve posted that sentiment a hundred times on Facebook. No one had better deny his adorable supremacy, right? Right. Now here’s something you don’t know about that cute canine goofball. He evolved those precious puppy dog eyes to manipulate you.
That’s what scientists now say, according to a new study published in the journal Proceedings of the National Academies of Sciences.
Domesticated dogs have evolved a specific muscle called the levator anguli oculi medialis, or LAOM, that allows them to raise their inner eyebrows. That muscle allows dogs to make their eyes appear larger, more appealing and almost helplessly baby-like.
You know that look well, because you see it all the time. You imagine that it’s saying “Couldn’t I have another treat?” or “Surely you don’t think it was me who left that odorous gift on the carpet while you were at work.” Who can say no to that face? You can’t, clearly.
Wolves, on the other hand, have never developed this muscle and don’t have such an expression. Why? They don’t need it. Wolves don’t depend on the kindness of humans for anything.
“What is so provocative about this finding is the likelihood that our unconscious biases shaped the evolution of the dog’s eye musculature,” Brian Hare, a Duke University evolutionary anthropologist and canine cognition expert, told The Washington Post. “The presence of these anatomical differences between wolves and dogs is a smoking gun for the role of our desire to cooperate and communicate with dogs being a driving force in dog evolution.”
Because soft tissue from thousands of years ago can’t often be found, the research team analyzed the facial musculature of wolf and dog cadavers they obtained from museums, taxidermists and a state wildlife organization. Refreshingly, there were no dogs or wolves killed for this research. The team discovered that the LOAM muscle so evident in domesticated dogs is, in wolves, only “a scant, irregular cluster of fibres.”
Behavioralists also studied humans interacting with domesticated dogs and captive wolves. They tracked the number of times the animal made the puppy dog eye expression during a two-minute interaction with humans. Dogs did it more frequently and with more intensity. It appears wolves can do it to a small extent, but they didn’t do it often.
How did dogs come to evolve this particular trait? In the 20,000 to 33,000 years since dogs and wolves split evolutionarily, it’s likely that humans responded with more interest, care and nurturing to dogs that looked cute and expressive, says the study. We chose to raise the pups who had this engaging appearance, ensuring the trait would carry on through dog generations to come.
We do this even today, picking the dogs with the sweetest expressions when we adopt one from an animal shelter.
“The findings suggest that expressive eyebrows in dogs may be a result of humans’ unconscious preferences that influenced selection during domestication,” lead author Dr. Juliane Kaminski said in a press release. “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.”
Earlier research showed that dogs use their eyebrows intentionally. They move them more when they’re interacting with us, but not when we’re ignoring them. If we’re paying attention to them, they’re engaging us with their eyes.
“It’s just that kind of behavior that causes lots of dog owners to think: ‘Oh my gosh, they want something. What do they need?’” Duquesne University biological anthropologist and study co-author Prof. Anne Burrows told The Washington Post.
“I’m speculating here, but the process of domestication must produce dog evolutionary changes much more quickly than evolutionary changes that you would see in the wild,” she added.
If we needed any further proof that human interaction with animals causes them to change, this is it. To ensure the dog/human bond, canines use their eyes in ways they don’t when we’re not around. They know they can get help or food if they just look at us and whimper.
Photo credit: Susan Bird