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Those Puppy Dog Eyes Are No Accident

The babyface dog is, according to a study of animal shelters, more likely to be adopted

Recent research has focused on a minor difference between dogs and wolves which might help explain why dogs are loved and wolves are not:

In the first detailed analysis comparing the anatomy and behavior of dogs and wolves, researchers found that the facial musculature of both species was similar, except above the eyes. Dogs have a small muscle, which allows them to intensely raise their inner eyebrow, which wolves do not. The authors suggest that the inner eyebrow raising movement triggers a nurturing response in humans because it makes the dogs’ eyes appear larger, more infant like and also resembles a movement humans produce when they are sad. Paper.(open access) Juliane Kaminski, Bridget M. Waller, Rui Diogo, Adam Hartstone-Rose, Anne M. Burrows. Evolution of facial muscle anatomy in dogs. Proceedings of the National Academy of Sciences, June 17, 2019; DOI: 10.1073/pnas.1820653116

University of Portsmouth, “The evolution of puppy dog eyes” at ScienceDaily

Dr. Kaminski had found earlier that dogs moved their eyebrows much more if humans were looking at them.

And what about wolves? The muscle that allows dogs to raise their eyebrows is “a scant, irregular cluster of fibres” in wolves. She notes,

“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.”

“The raised inner eyebrow movement in dogs is driven by a muscle which doesn’t consistently exist in their closest living relative, the wolf.

University of Portsmouth, “The evolution of puppy dog eyes” at ScienceDaily

In this case, “evolution” appears to mean that, over tens of millennia, humans embellished “a scant, irregular cluster of fibres” by selective breeding of dogs people like.

The resulting muscles, termed RAOL and LAOM, “form two short, straight lines, which connect the ring of muscle around a dog’s eye to either end of the brow above”:

Sometimes, the origins of changes like these aren’t immediately apparent. Certain physical dog traits—including floppy ears and short snouts—likely originate from the same set of developmental cells that code for tameness, a preferable trait in household pets, for instance. In the case of this new research, though, the connection between the physical trait and the related behavior is a bit more direct. “Previous work—and much of it by these same authors—had shown that these muscles were responsible for enhancing positive responses in humans,” Brian Hare, the director of Duke University’s Canine Cognition Center and the editor of the paper, told The Atlantic via email, “but the current suggests the origin of these facial expressions is after dogs split from wolves.”

HALEY WEISS, “Dogs’ Eyes Have Changed Since Humans Befriended Them” at The Atlantic

The ability to mimic a child’s appearance and behavior (“paedomorphism”) is a key advantage for a dog dealing with humans:

Gaze direction is a nonverbal channel of communication among humans; an infant quickly learns to look in the same direction of its parent. Dogs share that ability to a far higher degree than our closest primate relatives or the dog’s closest relative, the wolf. Dog, unlike their wolf cousins, seem to be more motivated to establish eye contact with humans and “mutual gaze between dogs and humans seems to be a hallmark of the unique relationship…”

Chuck Dinerstein, “Why Dogs Are Our Besties” at American Council on Science and Health

The babyface dog is, according to a study of animal shelter adoptions, more likely to be adopted.

One critic points out that the study involved dissection of the heads of only four wolves and six dogs:

The animals have a history of life experiences that may shape how they behave, Clive Wynne of Arizona State University who was not involved with the study tells the Post. Wynne says he is not completely convinced by this study and would like to see a larger sample of dogs and wolves with varying degrees of past experiences with humans, according to the Post. “A study that describes behavior between dogs or wolves and people has to explain the kinds of life experiences the individuals being tested have undergone.”

CHIA-YI HOU, “Domestication Might Have Sculpted Eyebrow Expressions in Dogs” at The Scientist

The researchers plan to study domestic foxes and coyotes next.

Design theorist Michael Behe, author of Darwin Devolves, adds another caution, that the underlying genetics is not examined. The study “is simply a description of dog and wolf anatomy.” The mutation that gets the shelter dog a new home may be stem from a degradation in the genome, as opposed to the addition it is assumed to be:

No studies were done to find the genetic alterations that led to the doggy ability. Thus it tells us pretty much nothing about the evolutionary mechanism. As I discuss in my new book, Darwin Devolves, many studies have shown that the genetic changes leading to the traits of various dog breeds — curly coat, shortened muzzles and legs, and more — are largely degradative. That is, the mutations mostly break or blunt pre-existing genes. For example, one mutation in dogs leads to increased muscle mass; it’s due to “a two-base-pair deletion in the third exon of MSTN leading to a premature stop codon at amino acid 313.” In other words, the increased muscle mass is due to a broken gene.

Michael Behe, “Puppy Dog Eyes for Darwin” at Evolution News and Science Today:

Not that lovers of those adorable puppy dog eyes will care much. The dog can’t talk but, it turns out, he doesn’t need to.

See also: Study: Cats DO recognize their names. They recognize them as signals but not as abstractions


Dogs are not as intelligent as seals, say some researchers.

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Those Puppy Dog Eyes Are No Accident